essay on migration of birds

Bird migration is one of nature’s great wonders. Here’s how they do it.

Some fly 11 days nonstop. Others trek 8,000 miles. Each year, thousands of bird species leave home in search of food.

Every spring and fall, a spectacle unfolds in the night sky as millions of birds attempt long, perilous journeys between their summer breeding and wintering grounds.

Most of the thousands of bird species that engage in this annual migration travel at night, when wind currents are smoother and the moon and stars guide their way.

The birds typically follow established flyways , generally north-south routes that offer the best opportunities for rest and refueling along the way.   Multiple bird species share these flight paths as they contend with rough weather, dehydration, starvation, and the threat of predation. ( Read more about the legendary treks of migratory birds .)

Arctic terns , for instance, undertake pole-to-pole roundtrips spanning more than 60,000 miles —a record, believed to be   the world’s longest migration of any animal . Other migrations involve birds flying east-west or up and down mountains. Even flightless birds migrate, such as the Adélie penguin , which makes a nearly 8,000-mile trek through frigid Antarctica.

Because migration is such an integral part of the avian life cycle, it was likely almost as prevalent thousands of years ago as it is today, says Martin Wikelski , director of the Max Planck Institute for Ornithology and a National Geographic Explorer .

Why some birds migrate and others don’t is the focus of a complex and active field of research. Finding food generally is believed to be the main driver. Additional motivations could include to escape from inclement weather and to reduce exposure to predators or parasites, especially during breeding season.

New technological advances, such as sophisticated GPS tags and radar-detection systems, are giving scientists unprecedented opportunities to observe bird migration.

As part of his ICARUS project , for instance, Wikelski has outfitted some birds with Fitbit-like devices that track their movements and the environmental conditions they encounter.

These miniature solar-powered satellite transmitters could one day reveal animal migrations and behavior at a global scale from space.  

“There’s just so much to learn,” Wikelski says. “I’ve been tracking birds for over two decades, and the ease with which birds seamlessly migrate between worlds is absolutely astounding.”

Which birds migrate?

Roughly half of the world’s nearly 10,000 known bird species migrate, including several songbirds and seabirds, waterfowl and waders, as well as some raptors. The Northern Hemisphere has the most diverse array of migratory birds .

Among the most well known are Arctic-breeding bar-tailed godwits, champions of endurance. In 2020, scientists recorded a godwit undertaking the longest-known nonstop migratory flight between Alaska and New Zealand, traveling more than 7,500 miles across the Pacific Ocean for 11 days straight. ( Learn why birds matter, and are worth protecting.)

There are also feathered migrants that fly far and fast. The great snipe, for instance, covers distances exceeding 4,200 miles and reaches speeds of up to 60 miles per hour when traveling nonstop between Europe and sub-Saharan Africa, making it the fastest flying migratory bird.

Even tiny birds embark on gargantuan journeys.   Calliope hummingbirds—North America’s smallest bird—make 5,600-mile roundtrips between the high-elevation meadows and open forests of the northern Rockies and the pine-oak forests of Mexico.

Most species of migratory birds may be partial migrants , meaning that some populations or individuals within the species migrate while others stay put. A fraction of American robins, for example, remain near their breeding grounds across seasons while others travel south and then return north.

Yellow-eyed juncos breeding at high elevations along southeastern Arizona’s mountains are most likely to migrate up to a mile downslope during severe snowy winters, compared to those at lower elevations facing fewer food constraints. Even tropical birds , especially insectivores, undertake short-distance elevational trips.

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How do they know where to go  .

In addition to following celestial cues, such as the position of the sun, stars, and the moon, adult birds use a magnetic compass to navigate. Even when there are no landmarks, this internal “GPS system” can prevent them from getting lost.

Such navigational acumen can enable individual birds to move through regions not typically traveled. In experiments, when solo-flying common cuckoos were transported nearly 1,500 miles away from their breeding grounds prior to migration, they often steered back to their normal migratory routes.

But what about inexperienced birds migrating for the first time? In one experiment, geographically displaced young common cuckoos navigated back to roughly the same flight path used by those birds that weren't displaced from their home.   ( Read about amazing animal navigators .)

Whether this navigational capacity is inherited and innate or learned is an ongoing debate . “I think it’s a combination of innate tendency, but you learn from others on the way,” says Wikelski, who has been tracking common cuckoos since 2012.

One way to learn might be tuning into nocturnal flight calls from other migrating birds. Distinct from a bird species’ regular vocalizations, these acoustic signals could especially guide the inexperienced, sometimes even those of other species, Wikelski says.

How do they know it’s time to go?  

For some birds, changes in environmental conditions, such as the length of the day, may trigger migration by stimulating hormones, telling the birds it’s time to fly.

Birds’ internal biological clocks can also detect when a season shifts, using cues such as changes in light and possibly air temperature.

Once the birds are in migration mode, a feeding frenzy ensues. This allows the birds to accumulate fat to power their journeys, says Lucy Hawkes , a migration scientist at the U.K.’s University of Exeter who currently tracks Arctic terns.

“Somehow, [the birds] know that they have to migrate soon and get massive,” Hawkes says.

Local and regional weather conditions , such as rain, wind, and air temperatures can also influence decisions about when migratory birds take to the skies.

Migrating in a changing world  

Overall, migration schedules seem to be shifting, as a result of climate change . “It looks like bird migrations are commencing a little earlier in the spring,” says   Kyle Horton, an aeroecologist at the University of Colorado who uses radar technology to map realtime and historical bird migrations in the United States.

Black-throated blue warblers, for example, are migrating almost five days earlier now, on average, than they did in the 1960s. Canada-bound American robins are arriving 12 days earlier in the spring than they did in 1994. Migrating whooping cranes are showing up nearly 22 days earlier at their stopover site in Nebraska in the spring and leaving almost 21 days later in the fall than they did in the 1940s. ( Learn how climate change has affected the annual migration of the yellow warbler .)

Such early starts to migration may benefit birds if plant and insect productivity at the breeding grounds mirror the trend. However, not all migratory birds may be able to adapt to a warming world, and if they did, the full costs of doing so remain unclear.

As scientists continue to unravel the mysteries of bird migration, the phenomenon remains one of nature’s great wonders.  

“They’re flying all night, feeding all day, and doing it again,” Horton says. “That’s sort of remarkable."

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A Brief History of How Scientists Have Learned About Bird Migration

Bird migration is one of the most fascinating and inspiring natural phenomena—but how do scientists figure out where all those birds are going?

From the earliest origins of bird banding to high-tech approaches involving genomic analysis and miniaturized transmitters, the history of bird migration research is almost as captivating as the journeys of the birds themselves. My book Flight Paths , forthcoming in 2023, will take a deep dive into the science behind these techniques and the stories of the people who developed them, but in the meantime, below you can read a selection of milestones that trace our unfolding understanding of migration.

Early History

Indigenous cultures develop a range of legends and stories about migratory birds. Athabascan peoples in Alaska, for example, tell the story of “Raven and Goose-wife,” in which Raven falls in love with a beautiful goose but cannot stay with her because he can’t keep up when the family of geese migrates south over the ocean.

While Aristotle correctly recognized some aspects of bird migration in his Historia Animalium in the 4th century, BC, he hypothesizes that swallows hibernate in crevices and that some winter and summer residents are actually the same birds in different plumages.

Inspired by Aristotle, Swedish priest Olaus Magnus suggests that swallows hibernate in the mud at the bottom of lakes and streams. This misconception will persist into the 1800s.

English minister and educator Charles Morton theorizes that birds migrate to the moon for the winter. Although this sounds ridiculous today, he correctly conjectured that birds may be spurred to move to new areas by changing weather and a lack of food and even noted that body fat might help sustain them on their journey.

John James Audubon ties silver thread to the legs of Eastern Phoebe nestlings and identifies them when they return to the same area the following spring—or, at least, so will later claim. Biologist and historian Matthew Halley cast doubt on this in 2018 when he noted that Audubon was actually in France in spring 1805 when the phoebes would have returned.

German villagers shoot down a White Stork that had a spear made of African wood impaled in its side. Dubbed the “pfeilstorch” (or “arrow stork”), this unfortunate bird provides some of the first concrete evidence of migration between continents.

Ornithologist William Earl Dodge Scott is touring the Princeton University astronomy department when he’s offered a view of the full moon through a telescope. Astonished to see migrating birds silhouetted against the face of the moon, he is able to use his observations to calculate a rough estimate of how high they must be flying.

Climbing a hill outside Madison, Wisconsin, historian and amateur ornithologist Orin Libby counts 3,800 calls by migrating birds over the course of five hours on one September night. Many of the calls seemed “almost human,” he will later write, “and it was not difficult to imagine that they expressed a whole range of emotions from anxiety and fear up to good-fellowship and joy.” These calls will eventually be dubbed “nocturnal flight calls" and be used as one way of monitoring bird migration.

Hans Christian Cornelius Mortensen places metal rings around the legs of starlings in Denmark to study their movements, the beginning of the scientific use of bird banding.

At a meeting in New York City, members of the American Ornithologists’ Union vote to form the American Bird Banding Association, the direct forerunner of today’s USGS Bird Banding Laboratory. Its mission is to oversee and coordinate bird-banding efforts at a national scale.

The U.S. Bureau of Biological Survey assumes authority over the bird banding program after the Migratory Bird Treaty Act passes in 1918. The agency's Frederick Charles Lincoln will use banding records from waterfowl to develop the concept of “migratory flyways”—four major North America flight routes around which bird conservation is still organized today.

David Lack and George Varley, biologists working for the British government, use a telescope to visually confirm that a mysterious military radar signal is being generated by a flock of gannets. It’s the first concrete proof that radar can detect flying birds, but the idea is not immediately embraced: “At one meeting,” Lack later writes, “after the physicists had again gravely explained that clouds of ions must be responsible, Varley with equal gravity accepted their view, provided that the ions were wrapped in feathers.”

Louisiana State University ornithologist George Lowery’s moon-watching observations in the Yucatan, using techniques inspired by Scott’s original full moon observations in 1880, provide evidence that some birds do indeed migrate across the Gulf of Mexico instead of taking a land route over Mexico.

Oliver Austin, an ornithologist leading wildlife management in Japan under the Allied occupation that followed World War II, describes the traditional Japanese method of catching birds for food using silk nets strung between bamboo poles. Mist nets will soon become the primary method for capturing songbirds for ornithological research. 

George Lowery and his collaborator Bob Newman oversee a massive effort to recruit volunteers across the continent to record moon-watching observations during fall migration. “Telescopes swung into operation at more than 300 localities as people by the thousands took up the new form of bird study,” writes Newman. “By the end of the season, reports had been received from every state in the United States and all but one of the provinces of Canada.” Due to the difficulties in analyzing such large amounts of data without computers, Lowery and Newman will not publish the full results until 1966. Their work provides the first continent-wide snapshot of migration patterns.

Illinois Natural History Survey ornithologist Richard Graber and engineer Bill Cochran record nocturnal flight calls for first time, rigging up a tape recorder with bicycle axles to hold the six thousand feet of tape needed to record a full night of migration.

Richard Graber tags a migrating Gray-cheeked Thrush in Illinois with a miniature radio transmitter developed by Bill Cochran. That night, he follows it for 400 miles in an airplane as it continues its migratory journey. “Each of us, at times, must stand in awe of mankind, of what we have become, what we can do,” Graber will write in Audubon . “The space flights, the close-up lunar photographs, the walks in space—all somehow stagger our imagination. I was thinking about this as I flew south from Northern Wisconsin [the next morning], having just witnessed an achievement of another kind by another species.”

Ornithologist Sidney Gauthreaux, who studied for his PhD under George Lowery, publishes “Weather radar quantification of bird migration,” the first systematic study of bird migration patterns using the relatively new technology of weather radar.

Bill Cochran tracks a radio-tagged Swainson’s Thrush for 930 miles on its migration, following it from Illinois to Manitoba over the course of a week in a modified station wagon with a radio receiver sticking out of the top.

Johns Hopkins University's Applied Physics Lab carries out the first field tests of satellite transmitters on birds using the  Argos satellite system —launched in 1978 for the purpose of tracking oceanic and atmospheric data. Swans and eagles are early subjects. 

British seabird biologist Rory Wilson tracks the movements of foraging penguins using a device of his own invention that he calls a Global Location Sensor. It uses ancient navigation principles to calculate and record a bird’s location using only a tiny light sensor and clock. These devices will later be better known as light-level geolocators.

Canadian scientist Keith Hobson and his colleagues publish a paper demonstrating that it’s possible to determine where a migrating songbird originated by analyzing the amount of deuterium—a rare isotope of hydrogen that occurs in varying amounts across the landscape—in its feathers.

“Selective availability,” a U.S. government practice which intentionally limits the accuracy of GPS technology available for non-military use, is switched off. Ornithologists quickly begin creating GPS devices for tracking the movements of birds.

The Cornell Lab of Ornithology launches eBird, a community science platform that lets birdwatchers upload records of what they observe to a database that is accessible to ornithologists, ecologists, and other researchers. Today more than one billion sightings have been contributed from around the world. 

A satellite transmitter implanted in a Bar-tailed Godwit dubbed “E7” tracks the bird’s astonishing nonstop 7,000-mile migration from Alaska to New Zealand over the open water of the Pacific Ocean—“the equivalent,” according to a USGS press release , “of making a roundtrip flight between New York and San Francisco, and then flying back again to San Francisco without ever touching down.”

Ornithologists Kristen Ruegg and Tom Smith launch the Bird Genoscape Project, an effort to map genetic diversity across the ranges of 100 migratory species. It will enable ornithologists to identify where in North America a migrating bird came from by analyzing its DNA.

The Cornell Lab of Ornithology scientists kick off the second iteration of BirdCast , a project that uses weather radar data to predict nights of especially intense bird migration activity. (The original BirdCast, started in 2000 by Sidney Gauthreaux, was discontinued after a year due to the limits of the technology available at the time.) One major result of the project is initiatives that encourage cities to shut off disruptive nighttime lighting when large numbers of migrating birds are likely to be on the wing.

The Motus Wildlife Tracking System , which uses miniature radio transmitters and an automated network of ground-based receiver towers, is launched in Canada. More than 30,000 animals (mostly birds) will be tracked by the system in the next decade.

Light-level geolocators  confirm  long-held suspicions that Blackpoll Warblers, songbirds that weigh roughly the same as a ballpoint pen, make a nonstop 1,400-mile, three-day flight over the eastern Atlantic Ocean during their fall migration from New England to South America.

Project Night Flight,  the largest nocturnal flight call monitoring project to date, operates more than 50 recording stations in Montana’s Bitterroot Valley. Spearheaded by Kate Stone and Debbie Leick, staff members at private research and conservation property MPG Ranch, Project Night Flight will record more than 100,000 hours of data in the next two years.

Icarus,  a new space-based wildlife tracking system with receivers on the International Space Station, begins operations. The initiative's overseers aim to provide transmitters that are lighter, lower-cost, and provide better-quality data than any trackers used before.

This piece originally ran in the Spring 2022 issue as “A Brief History of Discovery.” To receive our print magazine, become a member by  making a donation today .

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The Basics: How Birds Navigate When They Migrate

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Staying On Course

Birds have a remarkable homing instinct, allowing them to return to the same area year after year, even when their migration takes them halfway around the world. How this remarkable feat is accomplished has been the topic of many studies.

Young birds

Research indicates that young birds that do not migrate with their parents have an innate knowledge of the direction and distance they should travel, but lack a specific goal. After it arrives at its wintering grounds, the young bird will select a winter range to which it imprints during that winter. After the first year the bird has the ability to return to the same area, even if blown off course during migration.

Adult birds

Adults seem to have even more homing skills. Two classic experiments illustrate this point.

Manx Shearwaters were flown by plane from their nesting island off the coast of Great Britain to two different locations. One group was released near Boston, MA, and another near Venice, Italy. Shearwaters do not fly over land so both groups must have taken an over water route, which would be especially convoluted from Venice. Both groups of birds returned to their nesting burrows within 14 days, covering approximately 250 miles per day. How they were able to achieve this remarkable return is not fully understood.

In another experiment, several hundred White-crowned Sparrows were captured in their winter grounds near San Jose, California. One group was flown to Baton Rouge, Louisiana, and released, while a second group was flown to Laurel, Maryland, and released. The following winter thirty-four of the birds were recaptured in the same 1/4 acre plot in California they had been captured in originally, presumably after having visited their northern breeding grounds during the summer.

Homing Pigeon Studies

Homing pigeons have been used extensively as test subjects in order to develop a better understanding of migration and homing abilities. They have exhibited almost unbelievable navigation skills.

In one noted experiment, German scientist Hans Wallraff transported homing pigeons to a very distant location. To ensure that the birds did not receive any external navigational information, they were transferred under stringent conditions. The pigeons were transported in closed, airtight cylinders and provided bottled air. Light was turned on and off at random times and loud white noise was played. The cylinders were enclosed in magnetic coils that provided a changing magnetic field. Finally, the cylinders were mounted on a tilting turntable connected to a computer that varied both the rotation and tilt of the cylinders. After release at the distant and completely unknown area, the birds were able to fly home to their roost, apparently without trouble (other than an initial case of nausea).

The pigeons’ ability to fly home from a totally strange and distant location indicates that somehow the birds have both an internal compass and an internal map. A compass by itself would not be helpful, since the bird would not know if it were north, south, east or west of its home. The question of how a bird has a map of a location to which it has never been before (and was transferred to under such isolated conditions in the above test) and the sense of the direction it must take to return home remains a puzzle. Some possible explanations have been proposed, as follows:

Internal Maps

The nose knows theory.

How could a bird possibly have a map of places it has never been? One very surprising theory suggests that homing pigeons may use an olfactory map.

Visualize a pigeon in its home loft with the smell of pine trees from one direction and the smell of an onion farm in another. If the bird moves closer to the pine trees, the odor of pine will presumably grow stronger while the odor of onions grows weaker. In theory, a gradient map of odors could be created that would provide some directional information, even if the pigeon were suddenly dropped into a new location. Floriano Papi and others from the University of Pisa initiated this theory and have some evidence that olfactory navigation may extend to a distance of 310 miles. This theory remains controversial.

Magnetic map theory

A second theory suggests that birds use the earth’s magnetic field to obtain at least a partial map of its position. The earth’s magnetic field becomes stronger as you travel away from the equator and toward the poles. In theory, a bird might be able to estimate its latitude based on the strength of the magnetic field. While the change in strength is very small from one location to the next, there is some indication that homing pigeons have the sensitivity to detect even tiny changes in the strength of the magnetic field. Even if true, this would provide only a limited indication of the bird’s latitude.

At this time there is no clear evidence that either of these theories is the complete story and the mapping skills of birds remains largely unexplained.

The Compass

The other half of the navigation requirement is the compass. The internal map provides a bird with the general location of where it is relative to its homing or migration goal and its internal compass guides its flight and keeps it on course. Migrating birds are apparently utilizing several different compasses.

The sun compass

In 1951 Gustav Kramer discovered the sun compass. He performed his experiments by placing European Starlings in orientation cages and then used mirrors to shift the apparent location of the sun. In response, the birds shifted their migratory restlessness to match the compass direction indicated by the apparent new position of the sun.

Further research revealed that the bird’s sun compass is tied to its circadian rhythm. It seems birds have a time compensation ability to make allowances for changes in the sun’s position over the course of the day. This theory is supported by another experiment in which pigeons were placed in a closed room with an altered cycle of light and dark. Over a period of a few days their circadian rhythm was reset. The birds were then released on a sunny day. Because their “internal clock” had been reset, they misinterpreted the position of the sun and made a predictable error in their homing direction. The pigeons actually ignore the position of the sun relative to its position in the sky, relying on its azimuth direction, i.e. the compass direction at which a vertical line from the sun intersects the horizon.

Further study has also revealed that pigeons have to learn the sun’s path to use it in navigation. Young pigeons allowed to see the sun only in the morning lack the ability to use the sun for navigation in the afternoon.

The star compass

The sun compass plays a role in homing and may be used by birds that migrate during the day. Many songbird species, however, migrate at night. For many years scientist suspected that birds use the stars for navigation. In 1957 Franz and Eleanor Saur collected data from a series of experiments in which birds were placed inside an enclosed planetary dome. The Saurs were able to demonstrate that birds do use the stars for migration but not, as it turns out, in the way they thought. The common belief at the conclusion of the Saur experiments was that birds have a genetically coded map of the stars. In 1967 Cornell scientist Stephen Emlen used Indigo Buntings to prove that the actual story was a little different.

Dr. Emlen also used a closed planetarium for his tests. He started by collecting young birds and then hand raising them in a lab.  His research included the following:

A. One group of birds was raised in a windowless room and was never exposed to a point source of light.

B. A second group also never saw the sun but was exposed on alternate nights to a simulated night sky in the planetarium, with normal rotation around the North Star.

C. A third group was also raised in a windowless room, but on alternate nights was exposed to a simulated night sky in the planetarium. In this case, the sky was manipulated to rotate about a different star, Betelgeuse.

When the fall migration period started, the birds were released into a special cage inside the planetarium.

Group A was placed in the planetarium under a normal fixed sky. The birds oriented themselves in random directions, showing no ability to recognize a southerly migration direction.

Group B was placed in the planetarium with a normal rotation around the North Star. The birds oriented themselves away from the North Star, in the appropriate southern direction for migration.

Group C was also placed into the planetarium. They had been raised with Betelgeuse as the central point of rotation. When exposed to a normal sky these birds oriented themselves away from Betelgeuse.

This research indicates that young birds do not learn star patterns themselves but learn a north-south orientation from a rotational star pattern.

The Magnetic Compass

Another German team did research with the European Robin in the early 1960s. In their tests, robins showing migratory restlessness were placed in covered cages to eliminate sun, star and other light clues. Despite the lack of visual clues, the robins were observed hopping in the correct migratory direction.

As an additional refinement to the test, a Helmholtz coil was placed around the covered cages. The coil allowed the researchers to shift the direction of the earth’s magnetic field. When the direction of the magnetic field was changed, the robins changed their hopping direction.

Further research indicates that while birds can sense the north and south ends of a compass, they cannot tell the difference between the two. To determine which direction is north, the birds apparently have the capability to sense that the magnetic lines of force align toward the poles of the earth. They can also detect the dip in the lines of force as they approach the earth and, through some currently unknown method, seem to be able to detect and make navigational decisions based on the dip angle.

The Sunset Cue

Patterns of polarized light also appear to play a key role in navigation. Many of the nocturnal migrants start their flights at sunset or a little after. Birds apparently use the polarized light patterns to provide information on initial migratory flight directions.

Birds that migrate during the day often follow, and may recognize, natural landforms such as mountain ranges, rivers, and lakes.

There is some indication that birds use multiple compass methods and calibrate them against each other. Some species use one type of compass as the primary navigational aid while others rely on a different primary system. The complexity of migration and the skill with which it is accomplished is one of the many marvels that make birds so interesting to study.

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• 03 March 2021

A bird’s migration decoded

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Simeon Lisovski is at the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Polar Terrestrial Environmental Systems, 14473 Potsdam, Germany.

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Miriam Liedvogel is at the the Institute of Avian Research, 26386 Wilhelmshaven, Germany, and also at the Max Planck Institute for Evolutionary Biology, Plön, Germany.

Migration is a ubiquitous feature of the animal kingdom, and is arguably studied most comprehensively in birds. Writing in Nature , Gu et al . 1 provide a range of insights into possible factors driving the evolution of migration in peregrine falcons ( Falco peregrinus ). These birds are probably best known for their record-breaking flight speed, which reaches more than 320 kilometres per hour when they dive for prey while hunting.

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Nature 591 , 203-204 (2021)

doi: https://doi.org/10.1038/d41586-021-00510-4

Gu, Z. et al. Nature 591 , 259–264 (2021).

Article   Google Scholar  

Magnus, O. Historia de Gentibus Septentrionalibus (Giovanni Maria Viotto, 1555).

Google Scholar  

Bridge, E. S. et al. BioScience 61 , 689–698 (2011).

Bay, R. A. et al. Science 359 , 83–86 (2018).

Article   PubMed   Google Scholar  

Wilcove, D. S. & Wikelski, M. PLoS Biol. 6 , e188 (2008).

Delmore, K. E. et al. eLife 9 , e54462 (2020).

Ramenofsky, M., Campion, A. W., Pérez, J. H., Krause, J. S. & Németh, Z. J. Exp. Biol. 220 , 1330–1340 (2017).

Delmore, K. E. et al. Proc. R. Soc. B 287 , 20201339 (2020).

Mueller, T., O’Hara, R. B., Converse, S. J., Urbanek, R. P. & Fagan, W. F. Science 341 , 999–1002 (2013).

Grönroos, J., Muheim, R. & Åkesson, S. J. Exp. Biol. 213 , 1829–1835 (2010).

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The Avian Migrant: The Biology of Bird Migration

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The purpose of migration, regardless of the distance involved, is to exploit two or more environments suitable for survival or reproduction over time, usually on a seasonal basis. Yet individual organisms can practice the phenomenon differently, and birds deploy unique patterns of movement over particular segments of time. Incorporating the latest research on bird migration, this critical assessment offers a firm grasp of what defines an avian migrant, how the organism came to be, what is known about its behavior, and how we can resolve its enduring mysteries. The book clarifies key ecological, biological, physiological, navigational, and evolutionary concerns. It begins with the very first avian migrants, who traded a home environment of greater stability for one of greater seasonality, and uses the structure of the annual cycle to examine the difference between migratory birds and their resident counterparts. It ultimately connects these differences to evolutionary milestones that have shaped a migrant lifestyle through natural selection. Rather than catalogue and describe various aspects of bird migration, the book considers how the avian migrant fits within a larger ecological frame, enabling a richer understanding of the phenomenon and its critical role in sustaining a hospitable and productive environment. It concludes with a focus on population biology and conservation across time periods, considering the link between bird migration and the spread of disease among birds and humans, and the effects of global warming on migrant breeding ranges, reaction norms, and macroecology.

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• Migratory Routes and Patterns
• Communication
• Feeding Behaviors
• Mating and Breeding
• Types of Migration
• Navigational Techniques
• Migration Challenges and Conservation
• Social Structures
• Learning and Intelligence
• Sleeping Habits and Behavior
• Bathing & Preening
• Human Interaction
• Understanding Migratory Routes
• Major Migratory Routes
• Patterns of Migration
• Conservation of Migratory Routes

Journeys Across the Globe

Each year, billions of migratory birds switch between spring/summer breeding grounds and overwintering grounds, although their movements vary greatly between species and populations. Their journey may be just a few miles into a nearby valley or thousands of miles across the breadth of an ocean, but no matter the route, these birds rely on seasonal migrations for survival.

While some birds undergo somewhat random and nomadic movements, many follow highly predictable routes year after year, so identifying and protecting these pathways is increasingly important for bird conservation in the modern world.

This guide introduces the fascinating secrets of bird migration routes and patterns. Read along with us to learn about the eight major flyways and much more!

Pictured: A small flock of Barnacle Geese in-flight

Definition and Importance

A migratory route is the pathway birds choose to move between their breeding and overwintering grounds. These may be very direct where long-distance water crossings are involved, but many other factors come into play for birds migrating over land.

Many birds select routes that avoid major obstacles like ocean crossings, high mountains, and habitats that don’t provide their natural food sources.

Other birds choose routes that follow specific habitats, and large soaring birds like Golden Eagles may take advantage of certain features like mountain ridges to assist their flight.

Pictured: A Golden Eagle. A migratory route is the pathway birds choose to move between their breeding and overwintering grounds

Most medium and long-distance migrants move between high and low latitudes to take advantage of the changing seasons. The major migratory routes between these areas are simplified into units known as flyways. Each flyway includes the breeding range, migratory path, and overwintering range of the latitudinal migrants that use them.

Continue reading to learn about the world’s eight major flyways.

North & South American Flyways

Many North and South American birds are latitudinal migrants that move north and south, either crossing between the continents or remaining on either one. These migratory birds typically use the following important migratory routes or flyways:

Pacific Americas Flyway

The Pacific Americas Flyway passes through 18 countries, running from Alaska in the north and along the west coast of the United States, passing through Mexico and reaching Chile in South America. This flyway is used by many bird species, including the Surfbird and the Violet-green Swallow.

Central Americas Flyway

The Central America’s Flyway extends through 27 countries from the Arctic zones of Canada in North America to the Southern tip of South America, passing through Central America and the central regions of each continent. This flyway is used by over 380 different bird species, including the Whooping Crane and the Buff-breasted Sandpiper.

A Surfbird standing on a rocky mountain close to the shore

A family of Whooping Cranes, two adults, and one juvenile (middle), preparing for take-off

Atlantic Americas Flyway

The Atlantic Americas Flyway is used by nearly 400 bird species, including familiar birds like the Baltimore Oriole and Summer Tanager.

This important flyway extends along the East coast of North and South America, from Greenland to the southernmost tip of South America.

Crossing between the continents involves following the coast of the Gulf of Mexico or crossing the open ocean, with or without stops in the Caribbean.

The four flyways of North America

While the three flyways mentioned above link migrants between North and South America, four flyways are typically recognized in the United States. From west to east, these are the Pacific Flyway, the Central Flyway, the Mississippi Flyway, and the Atlantic Flyway.

Close-up of a Baltimore Oriole perching on a branch

The Summer Tanager is a medium-sized songbird

Eurasian Flyways

Over in Europe, Asia, Africa, and Australia, birds follow broadly similar north/south migration patterns to those seen in the Americas. These migrations may occur within each continent or see birds travel extraordinary distances between East Asia and the Southern tip of Africa or even from Western Alaska to New Zealand.

Continue reading to learn about the major Old-World flyways.

East Atlantic Flyway

The East Atlantic Flyway is used by about 300 hundred bird species and connects about 75 countries on four different continents.

This migratory pathway brings birds from the Arctic of Canada and Greenland in the west and Northern Russia in the east to the United Kingdom and other parts of Europe. It also connects Europe with Western and Southern Africa.

Black Sea & Mediterranean Flyway

This flyway connects Northern Asia and Central and Southern Europe with much of Africa and Madagascar. About 300 bird species use this massive flyway, which includes roughly 100 countries.

Long-distance migrants using this flyway may cross the Mediterranean Sea into Africa or use the Isthmus of Suez in Egypt to avoid a water crossing.

Pictured: A European Honey Buzzard - this species migrate south for the winter to sub-Saharan and southern Africa

East Asia/East Africa Flyway

About 331 bird species use this flyway linking Southern, Central, and Eastern Africa with Asia and even Alaska. Birds that use this route include long-distance migrants that travel the entire length of the flyway, as well as intra-African migrants that move between Eastern and Southern Africa.

Central/South Asian Flyway

This short flyway links central and northern Asia with the Indian Subcontinent in the south, remaining within the boundaries of the world’s largest continent.

Birds that migrate along this flyway must negotiate the Himalayas, which are the highest mountains on the globe. Some of the over 300 species that use this route circle around the Himalayas, while others fly directly over this formidable barrier.

East Asian/Australasian Flyway

Nearly 500 species migrate along this far eastern flyway that extends from the Arctic zones of Alaska and Eastern Russia in the north and New Zealand in the south.

Species that move between these continents must make ocean crossings ranging from a few hundred to several thousand miles!

Nearly 500 species migrate along this far eastern flyway which include the Bar-tailed Godwit (pictured)

Bird Corridors

Natural habitats vary across the landscape due to various factors, including altitude, local weather patterns, geology, drainage, and, increasingly, human development.

Bird corridors link areas of suitable habitat and create suitable pathways for migratory birds at a much finer scale than flyways.

Migrating birds may follow natural corridors such as mountain ranges or wooded river courses in arid areas. Managed corridors of natural habits through fragmented urban, agricultural, and industrial areas may provide safe passage for migratory birds passing over-developed areas.

Pictured: A Prairie Merlin. Migrating birds may follow natural corridors such as mountain ranges or wooded river courses in arid areas

Cyclical Patterns

Bird migrations are generally highly cyclical, with well-defined nesting seasons, overwintering periods, and predictable migration times and routes between these important life stages. These natural rhythms and routes have evolved to maximize the bird's chances of successfully reproducing and then surviving the periods of migration and overwintering.

The timing of their movements may vary slightly due to natural variations, but bird movements are generally guided by hormonal changes, day length, and predictable patterns like snowmelt, the thawing of waterbodies, the budding of deciduous plants, and the emergence of insects.

Navigational Patterns

How birds stay on course during migration has long fascinated ornithologists, and through clever scientific study, some of the secrets of bird navigation have been revealed.

Birds navigate using a combination of cues, including:

• Position of the Sun
• The center of rotation in the night sky
• The Earth’s magnetic fields and intensity
• Memory of landmarks
• An innate sense of direction

While rapid changes in the environment may impact a bird's ability to navigate by landmarks, they have less impact on their other navigational techniques. Failing to adapt could cause birds to stick to migratory routes that pass through areas with fewer and fewer resources.

Pictured: Flock of Canada Geese during migration

Threats to Migratory Birds

Migration is an essential behavior for a large proportion of the world’s birds, although their journey is filled with dangers like predation, exhaustion, and extreme storms.

The impacts of human population growth and development have put increasing pressure on birds by damaging their habitats. Habitat destruction and fragmentation are particularly harmful to migratory birds because many rely on specific environments throughout their migration paths.

Climate change also affects migratory birds negatively by altering their habitats and the timing of seasonal events like insect emergence and plant budding.

These events are critical in the breeding cycle of migratory birds, and arriving late at their breeding grounds can increase competition and decrease their chance of successful reproduction.

Conservation Efforts

At a local level, conserving migratory birds requires focused efforts to protect important habitats along flyways and corridors. This includes everything from growing native plants that support hungry Hummingbirds to engaging with landowners and the proclamation and management of protected areas.

On a broader scale, the conservation of migratory birds requires collaboration between various nations, both neighboring and distant.

International conventions like the Migratory Bird Treaty Act and the CMS (Convention on the Conservation of Migratory Species of Wild Animals) promote cross-border conservation.

Pictured: A Rufous Hummingbird. Conserving migratory birds requires focused efforts to protect important habitats along flyways and corridors

Whether skirting mountains, following river courses, or committing to long open-water crossings, migratory birds are on the move all across the globe.

Various bird species have evolved to use different migratory pathways and corridors, both within political boundaries and across continents.

However challenging it may be, it’s vital that natural habitats all along the length of these flyways are protected if migrating birds are to survive.

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Why migratory birds?

Avian migration is a natural miracle. Migratory birds fly hundreds and thousands of kilometres to find the best ecological conditions and habitats for feeding, breeding and raising their young. When conditions at breeding sites become unfavourable, it is time to fly to regions where conditions are better.

There are many different migration patterns. The majority of birds migrate from northern breeding areas to southern wintering grounds. However, some birds breed in southern parts of Africa and migrate to northern wintering grounds, or horizontally, to enjoy the milder coastal climates in winter. Other birds reside on lowlands during the winter months and move up a mountain for the summer.

Migratory birds have the perfect morphology and physiology to fly fast and across long distances. Often, their journey is an exhausting one, during which they go to their limits. The Red Knot has one of the longest total migration routes of any bird, travelling up to 16,000 kilometres twice a year. It breeds in Siberia and overwinters on the west coast of Africa, some even going down to the tip of South Africa.

It is truly amazing how migratory birds can navigate with pin-point accuracy. Exactly how migrating birds find their flyways is not fully understood. It has been shown that they are able to orientate by the sun during the day, by the stars at night, and by the geomagnetic field at any time. Some species can even detect polarized light, which many migrating birds may use for navigation at night.

Why Migratory Birds Need Protection

Migration is a perilous journey and involves a wide range of threats, often caused by human activities. And as diverse as people and their habits in different countries are, so are threats the birds face. As migratory birds depend on a range of sites along their distribution area, the loss of wintering and stopover sites could have a dramatic impact on the birds’ chances of survival.

Flying long distances involves crossing many borders between countries with differing environmental politics, legislation and conservation measures. It is evident that international cooperation among governments, NGOs and other stakeholders is required along the entire flyway of a species in order to share knowledge and to coordinate conservation efforts. The legal framework and coordinating instruments necessary for such cooperation is provided by multilateral environmental agreements such as CMS and AEWA .

World Migratory Bird Day has a global outreach and is an effective tool to help raise global awareness of the threats faced by migratory birds, their ecological importance, and the need for international cooperation to conserve them.

This site is maintained by the UNEP/CMS Secretariat and UNEP/AEWA Secretariat © 2006 - 2022     Disclaimer | Impressum UNEP/CMS and UNEP/AEWA Secretariat | Platz der Vereinten Nationen 1, 53113 Bonn, Germany | Tel. (+49 228) 815 2454, Fax. (+49 228) 815 2450 |  Contact

Audubon Adventures

Background for Teachers

Most of the approximately 700 avian species that breed in the United States and Canada spend much of the year migrating between breeding ranges and wintering ranges. Among these travelers are more than 350 neotropical migrants—birds that breed in Canada and the United States and spend winter in tropical parts of Central and South America and the Caribbean.

Time: Late spring. Place: A tidal marsh near the coast of North Carolina. A large bird probes in the mud with its downward-curving bill, searching out worms, crustaceans, and mollusks. This Whimbrel is stopping to feed as it makes its way from its winter home in the Caribbean to the Arctic tundra, where it will breed and raise its young with its lifelong mate.

On any day, birds are migrating somewhere, but spring and fall are the busiest seasons—a time when billions of birds wing their way through the skies, day and night. Birds that migrate do so because it’s proven to be an effective strategy for survival and reproduction.

Insect-eating land birds, for example, can’t depend on a steady supply of insects during a northern winter. Nor can a nectar-feeder, such as a hummingbird, rely on flowers. By migrating to tropical regions, however, they can tap into resident birds’ year-round supply of food.

Why, then, don’t migrants stay put in springtime? Because staying means competing for a limited supply of nest sites and food during the breeding season, when birds need a plentiful supply of protein-rich food to feed their young. By migrating farther north, however, birds can exploit a new crop of insects and nectar-laden flowers. In Arctic regions, for example, huge numbers of insects take advantage of warmth and long sunny days to fulfill their own breeding and feeding needs.

Thus, insect-eating birds benefit from an incredible seasonal abundance of food. Likewise, migratory raptors can prey on spring’s bounty of rodents, fruit- and nectar-feeding birds find fresh meals, and fish-eating seabirds and plant-eating waterfowl also benefit by traveling to where the getting is good.

Challenges and Threats

While the benefits of migration are substantial, migratory species pay a price for them. Migration is hazardous and exhausting. Of the more than 5 billion individual birds that migrate south for the winter, it’s estimated that about half (mostly young birds from the previous breeding season) do not make it back to their breeding range in spring. Some of these birds die due to natural causes: disease, predation, bad weather, storms that blow them off course. But human activity has added to the perils faced by migrants.

Time: Early summer. Place: An eastern Tennessee forest. A Wood Thrush lands on the edge of its nest, greeted by the gaping mouths of its hungry hatchlings. In the fall, they will all head south toward Central America. When they reach the coast of the Gulf of Mexico, they will fly across it nonstop.

Some birds are weakened or killed by pesticides. In the mid-1990s, for example, thousands of Swainson’s Hawks died on their Argentinean winter range, poisoned by a pesticide used to kill grasshoppers, the birds’ main prey; more than 20,000 hawks—5 percent of the world’s total population—perished. Brightly lit high-rise buildings are another major threat to migrating birds. In May 2017, nearly 400 migrating warblers were killed in a single night when they crashed into a high-rise building in Galveston, Texas.

The biggest threat to birds, however, is the loss and fragmentation of habitat in breeding and wintering ranges and along migratory routes. Coastal development, deforestation, oil production, ranching, and conversion of grasslands to farmlands (and wild areas and farmlands to paved developments) all take a toll on habitat, not only in breeding and wintering areas, but in the places they stop during migration to rest and feed. Increasingly, climate change is being examined as a threat factor. The population of the endangered Piping Plover is estimated to be about 8,000 individuals. Their breeding grounds along the Atlantic Coast face not only degradation and destruction because of human development, but because of rising seas associated with a warming climate.

Audubon’s 2014 report, Birds and Climate Change , found that more than half—314 species—of the 588 North American bird species studied are in trouble because of global warming. The changing climate is altering habitat and reducing birds’ ranges, putting them at risk. An example is the Pacific Brant, which appears to be changing its migratory habits as a result of warmer temperatures and more food on its winter range. About 30 percent of the Pacific Brant population now winters in Alaska instead of flying south to Mexico.

Acting to Identify and Reduce the Threats

Many efforts are underway to combat threats to migratory birds described above. Argentina, for example, restricted the use of the pesticide that killed Swainson’s Hawks in the 1990s, and banned it in 2000. The problem of bird collisions with windows was first recognized in Toronto, Canada, leading to the establishment of FLAP (“Fatal Light Awareness Program”). In the United States, a project called “Lights Out” has a similar mission: to reduce bird collisions with windows, especially in high-rise buildings. In cities all across the country, building owners and managers are turning off excess lighting at night during the months migrating birds are passing through. On the local level, birders, schools, and other community organizations work to protect local habitats.

Time: Early fall. Place: The foothills of the Rocky Mountains. A tiny Rufous Hummingbird dips its long bill into a nectar-filled flower. It is pausing here to refuel on its annual fall migratory journey of nearly 4,000 miles from Alaska to Mexico.

Given the global nature of the threats and the fact that birds are world travelers, cooperation across international borders is essential to identifying threats and protecting birds throughout their ranges. An example is Audubon’s partnership with the Virginia Tech Shorebird Program and the Bahamas National Trust to map the migratory journeys of banded Piping Plovers in order to identify breeding, stopover, and wintering grounds in the United States, the Bahamas, and the Caribbean. That’s the first step in monitoring and taking steps to protect essential habitat for the endangered plovers.

On local and global levels, the effects of climate change on migratory birds will continue to be studied. Cutting down on factory and automobile emissions, conserving energy whenever possible in homes and businesses, and other efforts to combat global warming will benefit not only migratory birds but all living things. The same is true for actions at all levels that conserve and protect habitat for birds, other wildlife, native plants, and human beings.

Photos: Frank Leung/iStock; Kajornyot Krunkitsatien/AdobeStock; Ashley Peters.

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Bird Migration: Definition, Types, Causes and Guiding Mechanisms

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In this article we will discuss about the Migration of Birds:- 1. Definition of Bird Migration 2. Types of Bird Migration 3. Causes 4. Guiding Mechanisms 5. Disadvantages.

• Disadvantages of Bird Migration

1. Definition of Bird Migration:

The word “migration” has come from the Latin word migrara which means going from one place to another. Many birds have the inherent quality to move from one place to another to obtain the advantages of the favourable condition.

In birds, migration means two-way journeys—onward journey from the ‘home’ to the ‘new’ places and back journey from the ‘new’ places to the ‘home’. This move­ment occurs during the particular period of the year and the birds usually follow the same route. There is a sort of ‘internal biological clock’ which regulates the phenomenon.

Definition :

According to L. Thomson (1926), bird migration may be described as “changes of habitat periodically recurring and alter­nating in direction, which tend to secure optimum environmental conditions at all times” .

Bird migration is a more or less regular, extensive movements between their breeding regions and their wintering regions.

2. Types of Bird Migration:

All birds do not migrate, but all species are subject to periodical movements of vary­ing extent. The birds which live in northern part of the hemisphere have greatest migra­tory power.

Migration may be:

(i) Latitudinal,

(ii) Longitudinal,

(iii) Altitudinal or Vertical,

(iv) Partial,

(vi) Vagrant or Irregular,

(vii) Seasonal,

(viii) Diurnal and

(ix) Noctur­nal.

(i) Latitudinal migration:

The latitudinal migration usually means the movement from north to south, and vice versa. Most birds live in the land masses of the northern temperate and subarctic zones where they get facilities for nesting and feeding during summer. They move towards south during winter.

An opposite but lesser movement also occurs in the southern hemisphere when the seasons are changed. Cuckoo breeds in India and spends the summer at South-east Africa and thus covers a distance of about 7250 km.

Some tropical birds migrate during rainy season to the outer tropics to breed and return to the central tropics in dry season. Many marine birds also make considerable migra­tion. Puffinus (Great shearwater) breeds on small islands and migrates as far as Greenland in May and returns after few months.

It covers a distance of 1300 km. Penguins migrate by swimming and cover a considerable distance of few hundred miles. Sterna paradisaea (Arctic tern) breeds in the northern temperate region and migrates to the Antarctic zone along the Atlantic. It was observed that Sterna covers a distance of 22 500 km during migration!

(ii) Longitudinal migration :

The longitudinal migration occurs when the birds migrate from east to west and vice- versa. Starlings (Sturnus vulgaris), a resident of east Europe and west Asia migrate towards the Atlantic coast. California gulls, a resident and breed in Utah, migrate westward to winter in the Pacific coast.

(iii) Altitudinal migration :

The altitudinal migration occurs in moun­tainous regions. Many birds inhabiting the mountain peaks migrate to low lands during winter. Golden plover (Pluvialis) starts from Arctic tundra and goes up to the plains of Argentina covering a distance of 11 250 km (Fig. 9.54).

Birds migrate either in flocks or in pairs. Swallows and storks migrate a distance of 9650 km from northern Europe to South Africa. Ruff breeds at Siberia and travels to Great Britain, Africa, India and Ceylon thus travelling a distance of 9650 kilometers.

(iv) Partial migration:

All the members of a group of birds do not take part in migration. Only several members of a group take part in migration. Blue Jays of Canada and northern part of United States travel southwards to blend with the sedentary populations of the Southern States of U.S.A. Coots and spoon bills (Platalea) of our country may be example of partial migration.

(v) Total migration :

When all the members of a species take part in the migration, it is called total migration.

(vi) Vagrant or irregular migration :

When some of the birds disperse to a short or long distance for safety and food, it is called vagrant or irregular migration. Herons may be the example of vagrant or irregular migration. Other examples are black stork (Ciconia nigra), Glossy ibis (Plegadis falcinellus), spotted eagle (Aquila clanga), and bee eater (Merops apiaster).

(vii) Daily migration :

Some birds make daily journey from their nests by the influence of environmental factors such as temperature, light, and humidity also. Examples are crows, herons and starlings.

(viii) Seasonal migration :

Some birds migrates at different seasons of the year for food or breeding, called seasonal migration, e.g., cuckoos, swifts, swallows etc. They migrate from the south to the north during summer. These birds are called summer visitors. Again there are some birds like snow bunting, red wing, shore lark, grey plover etc. which migrate from north to south during winter. Th ey are called winter visitors.

Nocturnal and Diurnal Flight :

(i) Diurnal migration :

Many larger birds like crows, robins, swal­lows, hawks, jays, blue birds, pelicans, cranes, geese, etc. migrate during daytime for food.

These birds are called diurnal birds and gene­rally migrate in flocks.

(ii) Nocturnal birds :

Some small-sized birds of passerine groups like sparrows, warblers, etc. migrate in darkness, called nocturnal birds. The darkness of the night gives them protection from their enemies.

3. Causes of Migration :

Most species of birds migrate more or less on schedule and follow the routes in a regular fashion. The actual causative factors deter­mining the course and direction of migration are not clearly known.

The following factors may be related to the problems of migration:

i. Instinct and Gonadal changes :

It is widely accepted that the impulse to migrate in birds is possibly instinctive and the migration towards the breeding grounds is associated with gonadal changes.

ii. Scarcity of food and day length:

Other factors, viz., scarcity of food, shortening of daylight and increase of cold are believed to stimulate migration. Migration in birds depends upon two important factors— stimulus and guidance.

Scarcity of food and fall of daylight are believed to produce endocrinal changes which initiate bird migration.

iii. Photoperiodism:

The increase of day length (Photoperiodism) induces bird’s migration. The day length affects pituitary and pineal glands and also caused growth of gonads which secret sex hormones that are the stimulus for migration. In India, Siberian crane, geese, swan those come from central Asia, Himalayas, begin to return from March and onwards with the increase of day length.

iv. Seasonal variation:

The north-to-south migrations of birds take place under stimulus from the internal condition of the gonads which are affected by seasonal variation.

The experiments of Rowan with Juncos (summer visitor to Canada) have esta­blished that light plays an important role in the development of gonads, which has indirect role on migration. If the gonads undergo regression, the urge for migration is not felt. So the seasonal changes in illumination appear to be a crucial factor for determining migration.

Despite all these suggestions, it is not clear how birds — through successive generations — follow the same route and reach the same spot. The instinctive behaviours like migration, breeding, moulting are phasic occurrences in the annual cycle which are possibly controlled by the endocrine system. In all migratory birds, accumulation of fat takes place for extra fuel during prolonged flight in migration.

4. Guiding Mechanisms in Bird Navigation :

For more than a century the celestial navigations of birds have fascinated the ornithologists. Different explanations have been advanced to explain how birds navigate. It is difficult to generalize on the means of orientation and navigation in migration. The different groups of birds with different modes of existence have evolved different means of finding their way from one place to another (Pettingill, 1970).

The other reasons may be:

Fat deposition :

Migratory birds become greedy and fat is deposited in the subcutaneous region of the body. The fat deposition plays an important role in the migration of birds. Birds, those migrate a long distance, reserve enough fat which provides energy in their arduous jour­ney and helps the birds to reach its desti­nation, following a particular route. After fat deposition, restlessness (Zugunruhe) is seen among birds for migration.

Inherited instinct :

Birds that take part in migration or follow a more or less definite goal, evidently possess an inherited instinct. Both the direction and the goal must have been implanted in the bird’s genetic code when a population can adjust to a particular location or environment.

Experienced Lead the Flock :

The theory is sometimes advanced that old and experienced birds lead the way and thereby lead the whole route and show the whole route the younger generation. This the­ory may be applicable to some birds like swans, geese and cranes because they fly in flocks but not applicable in all species where old and youngs migrate at different times and mainly youngs start ahead of the adult.

Werner Ruppell of Germany, a leading experimenter on avian migration, found that Starlings of Berlin find their way back to their nestling places from about 2000 km away. A sea bird named Manx shearwater collected from the western coast of England after being flown by plane to Boston was found back in its nest in England within 12 days.

The shearwa­ter had flown its own way about 4940 km across the unknown Atlantic Ocean! The gold­en plover of North America migrates from its winter home in the Hawaiian islands to its breeding place in northern Canada.

This bird lacks webbed feet and it is quite natural that it must fly for several weeks over thousands of kilometers of ocean to reach its destination. The birds have wonderful power of navigation and orientation to find their destination even under odd conditions.

There are many theories regarding the phenomenon of migration in birds.

Various theorists propose that birds are guided by a number of agencies:

a. Earth’s magnetic field—as the guiding factor:

Some ornithologists believed about the existence of a “magnetic sense” as the impor­tant factor in the power of “geographical orientation”. The theory was conceived as early as 1885 but conducted by Yeagley in 1947 and 1951. Yeagley suggested that birds are sensitive and guided by the earth’s mag­netic field.

The Coriolis force arising from rotation of the earth plays the guiding role in migration of birds. The basic question of the theory may be asked — “can birds detect such minute differences in the earth’s magnetic field and can these forces affect bird’s behaviour?”

Attempts to demonstrate by experimental evidences have not supported Yeagley’s experiment. Experiments, in which the earth’s magnetic field was changed, had no effect on the direc­tion which the birds undertook.

b. Sun—the guiding agent in diurnal migration:

The concept that birds are guided by the position of the sun was advanced by Gustav Kramer in Germany and G. V. T. Matthews in England. They have shown by intensive experimentations those homing pigeons and many wild birds use the sun as the compass and that they possess a ‘time sense’ or ‘internal clock’ which allows them to take account of motion of the sun across the sky.

Kramer (1949, 1957, 1961) performed experiments on Starlings (diurnal migrants) and showed that these birds use the sun for setting their migratory course. When the sky remains clear, the Starlings succeed in taking the right direction.

If the sky remains overcast they become bewildered and fail to orient themselves. Mechanical placement of a mirror which deflects rays of the sun result into con­siderable deviation of orientation to a pre­dictable extent. The experiments of Kramer and others failed to explain the navigation and orienta­tion of night migrants. This aspect was exten­sively worked out by E.G.F. Sauer (1958).

c. Stars—the guiding agent in nocturnal migration:

The warblers and many other birds orient themselves during navigation by the sun during daytime. But the warblers as well as many other birds navigate mainly at night. What sorts of system do these birds use to the pathways during navigation at night?

Sauer performed experiments on white throat warblers to give an insight to the prob­lem. Sauer put the birds in a cage placed in a planetarium having an artificial replica of natural sky. When the light of the planetarium was poorly illuminated, i.e., when the stars were not visible, the warbelers failed to orient themselves.

When the illumination was better and the planetarium sky matched with the natural night sky, the birds followed up the proper direction. It has also been shown by Sauer that a warbler which has spent its life in a cage (i.e., never navigated in natural sky) has an inborn ability to follow the stars to navigate along the usual route the members of the species follow.

Sauer has suggested that the warblers possess hereditary mechanism to ori­ent themselves by the stars during nocturnal migration. The warbler can adjust the direc­tion perfectly at the latitude.

Suggestions have been advanced by many workers that the configuration of the coastline possibly helps in navigation, but Sauer has dis­proved the idea and advocated that the birds are exclusively guided by the stars during night.

d. The ‘compass’ and the ‘internal clock’ in bird migration:

It is a known fact that mil­lions of birds fly to their winter ‘home’ in every autumn. In doing so they cover often thou­sands of kilometers from their native ‘home’. In the following spring they again return to their breeding grounds. This is a regular bio­logical phenomenon in avian life.

It has been established that the young birds caught during migration, when released afterwards, follow exactly the original route their undisturbed fellows followed. This phe­nomenon suggested the presence of a sort of ‘compass’ the birds use during navigation.

But Kramer’s experiment gave a clue to the problem. The position of the sun is vital in con­trolling the navigation pathways. During the day the position of the sun in the sky is changed from east to west via the south. Despite such changes birds tried to navigate in the same direction. This means they have the inherent ability to make appropriate allowance for the time of day.

How do the birds know the time of day? They have possibly a built-in time­keeping mechanism (internal clock) which is synchronized with the earth’s rotation. The ‘internal clock’ can be made to synchronize with external happenings.

Existence of biological clocks is a pro­perty of living organisms. It is not confined to animals, it is found in plants and even in sim­ple cells too. It is a common experience that if we are in the habit of getting up every day at a particular time, we frequently wake up at the same time. Besides, many of our bodily func­tions have a rhythm of their own. These are possibly controlled by an ‘internal clock’ of which we are normally unaware.

Telemetry means methods of tracking of the movement of birds or other migratory ani­mals by using radio. This is the most promising method that has been applied to trace the route of bird’s migration. The method consists of attaching a small radio transmitter, weighing about 2-3 gm. that sends periodic signals or “beeps”.

The miniature transmitter can be placed on birds and it does not interfere flight and the signals can be detected by means of a receiving set mounted on vehicles or aero planes that can detect the routes of migratory birds.

Though there are some limitations of telemetry but this technology gives encoura­ging results. More recently researchers are engaged largely to track the routes of the migratory birds with the aid of satellites and radar tracking instruments.

5. Disadvantages of Bird Migration:

i. Many youngs are not, able to reach the destination because they die during the course of the continuous and tiresome journey.

ii. Sudden changes in the climate such as storms and hurricanes, strong current of wind, fog are the causes for the death of a sizeable number of migrants.

iii. Sometimes man-made high tours and light houses cause the death of migratory birds.

iv. Man themselves are responsible for the death of the migrants. They shoot at these poor birds just for their own leisure and amusement.

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• Bird Migration

CCB is a leader in conservation research involving bird migration

Populations of many migratory birds depend not only on places to breed and spend the winter but also on the quality and continued availability of habitats along migration routes. The importance of identifying and protecting these non-breeding habitats has been recognized by conservation organizations throughout the world and represents a formidable international conservation challenge. CCB continues to be a leader in migration research.

The broad objectives of our research program are to determine 1) the location of migratory pathways, 2) the resource and habitat requirements of birds in passage and 3) the ecological role that geographic areas play in the lifecycle of migrant species.

Whimbrel flying over Boxtree Creek on Virginia’s Eastern Shore, heading north to their Arctic breeding grounds. Photo by Alex Lamoreaux.

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Essential Migration: A Study of Surjeet Kalsey’s “Migratory Birds”

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Migratory Birds

About the basics of bird migration.

Our world is full of biodiversity, we can see different kinds of birds, animals and plants all around us. There are different species of animals and plants that use various strategies to survive and keep the cycle of life going. One such strategy that birds use is called migration. Migration is a regular seasonal movement of birds in large groups. 

It happens in the case of migratory birds when they have to leave their home place to migrate to some other favourable place and for that, they have to adopt a long journey in which there is no guarantee whether they will be able to return back or not but if they do not migrate, in that case as well, their survival is not possible, thus they used to have migrated in any case. In this article, we will be talking about migratory birds and all about their migration. This article will help you to understand one of the most important behavioural patterns of the animal world, and will increase your subject knowledge as well.

What is Migration?

Migration of birds is one of the most fascinating phenomena in which birds travel from one habitat to another in search of favourable conditions and increased resources for survival and it also involves the journey to return to the original place. It also happens during seasonal change or movement between breeding and non-breeding locations. Migration is not an easy process, as birds have to cover long distances in order to reach their destinations and during these journeys, they need a lot of energy, food, water, sufficient rest, etc and not all the migration journeys become successful and some of the birds die as well in these journeys.

What are Migratory Birds?

Those birds who migrate from one location to another location in order to breed, feed, and raise their offspring, are known as migratory birds. They usually migrate from unfavourable locations to some favourable places which are having suitable conditions along with sufficient food and water resources and are also safe as well. The majority of the birds migrate during the breeding season and others migrate for food resources and because of change in seasons.

Types of Migrating Birds

The types of migrating birds can be judged through the type of migration they adopt which can be cleared from the following:

Seasonal Migration: It happens with the change in seasons. Birds migrate from a location when they are not able to survive in harsh conditions.

Latitudinal or Longitudinal: This kind of migration happens between different latitudinal or longitudinal locations. Either North to South or East to West or vice - versa.

Altitudinal: It generally happens for those birds who give birth at high altitude areas, and when they have to migrate again because of the harsh conditions over there.

Loop: Those who follow this kind of migration, those birds usually follow annual migration in a cycle again and again to enjoy the resources of two locations.

Nomadic: Understanding exact patterns and their timings are not easy, they stay in one place until sufficient resources are available otherwise they will migrate.

LeapFrog: It is a kind of skip migration in which birds migrate to long distances in order to skip a sedentary population.

Reverse: Aberration among birds is seen when they are confused and choose an unexpected path and go in the opposite direction.

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Features of Migratory Birds

These birds are known to have good morphology as well as physiology because of which they can cover long distances by flying fast and observing various other things.

They have the ability to navigate things with good accuracy. They use the sun, the stars, the Earth's magnetism, etc.

They know when to migrate and when to return. For their specific reasons, they do not hesitate to migrate to far present locations.

They can fly as far as 16000 miles and some of the birds fly at a speed of 30mph to reach their destination. With this speed, they can reach in 533 hours whereas if they fly on the Basis of 8 hours per day, they can reach the final destination in 66 days.

They fly at different speeds and at different altitudes. Some fly at low altitudes where we can see them whereas some birds fly at high altitudes as well such as Songbirds who travel at 500 to 2000 feet whereas if we talk about Geese or Vultures, they used to fly at 29,000 to 37,000 feet altitudes.

Before migration, they prepare themselves for the journey by increasing their body weight or by keeping food reserves.

Different birds migrate at different timings but most of the birds prefer to fly at night because usually, the night is much safer for them due to fewer predators or having cooler air at night with which they can fly and rest easily.

They also prepare for their return as well because, after exhaustion of their whole energy in the long-distance journey, they usually feel hungry and require food and water.

Why do Birds Migrate?

There are several reasons, a few of which are mentioned below:

Food is one of the major reasons for their migration. If they all stay at one place then food will be exhausted & scarce during the breeding time and thus breeding will be less successful. Thus, they migrate to food-abundant areas.

During the nesting season, the depletion of food will not only affect the adult birds but also attract a lot of predators because they become an easy meal for them.

Birds usually migrate for their family or we can say for healthy breeding. They always require healthy conditions for raising their offspring. These conditions depend upon different species such as sources of food, weather, habitat , adequate shelter, breeding colonies, safety, etc.

Another reason can be a change in the climatic conditions. Any severe change in these conditions can cause their migration because it makes it difficult for them to survive in harsh conditions be it extra warm or extra cold.

They also can migrate to save themselves and their offspring from predators and diseases. They usually migrate to places that are inaccessible to predators.

How do Birds Migrate?

They make different physical adaptations for the travel journey such as building extra fat supplies to provide extra energy during the journey.

Keeping food and water reserves by increasing their body weight before the migration and this phenomenon of increasing weight is known as hyperphagia and a lot of birds experience this phenomenon.

They also shed their old feathers in order to make their flight easy so that it takes less energy to fly.

They used to change the altitudes as well. They fly at higher altitudes for a speedy and fast journey.

They change their behaviour of flying as well. Sometimes those birds who used to fly in the day, during migration fly at night.

Sometimes they also fly in a V pattern or we can say in a group by following the leader who has much experience and this pattern makes the journey much easier.

Migratory Birds With Names

Let's see some of the examples of migratory birds which are mentioned below:

Siberian cranes and Greater flamingo are migratory birds that are usually seen in India in the winter season.

Asiatic Sparrow Hawk migrates to India and Myanmar during winters.

Swallow, which is a small bird, migrates from Southern England to Southern Africa.

Red Wing lives in Eurasia or the Himalayas but flies to Africa in Winter.

Sand Martin that live in Eurasia or North America usually migrate to southern areas which depend on their zones.

Whinchat who lives in Europe flies to Africa between October to March.

Common Rosefinch lives in Eurasia and flies to southern parts of Asia in Winters.

Names of other migrating birds are Black-headed gull, Green Sandpiper, Northern Lapwing, Eurasian Hobby, Gray Heron, etc.

Threats and Conservation of Migratory Birds

When birds migrate from one place to another there can be many threats to them. It took a lot of energy to cover these long-distance journeys. The major threats include exhaustion, starvation, injuries, threats from predators or hunters, diseases, pollution, natural calamities or disasters, etc.

For their conservation, we have CMS which means Convention on Migratory Species at the international level which is also famous as the Bonn convention which aims to protect migratory species such as territorial, avian, or marine,  throughout their ranges and all the countries coordinate with each other for their conservation.

To sum up we can say that avian migration is not an easy task but also important for the birds as well. They require favourable conditions in order to survive and raise their young ones for which they adopt long journeys which are exhausting for them and in these journeys they have to cross the boundaries which can lead to more problems and threats for them and for which every country should adopt conservation measures for them. In this article, we have covered everything about migratory birds, why and how birds migrate, several features, their examples, etc. We believe that this comprehensive article will help you to understand this important topic and you will also think about the conservation of these species.

Migratory Birds - Survival out of their Habitat

The birds who migrate from one unfavourable location to some favourable location in order to breed, feed, and raise their children are known as migratory birds. They migrate to some locations which are having abundant food and water resources with good climatic conditions. They make different physical adaptations for the travel journey such as building extra fat supply and keeping food and water reserves by increasing their body weight before the migration. 

Migratory birds shed their old feathers in order to make their flight easy and on the other hand, they used to change their attitudes as well. They fly at higher altitudes for a speedy and fast journey along with the change in their behaviour of flying as well. Sometimes those birds who used to fly in the day, during migration fly at night. Sometimes they also fly in a V pattern or we can say in a group by following which makes the journey much easier. Some of the examples of migratory birds with names are the Black-headed gull, Green Sandpiper, Northern Lapwing, Eurasian Hobby, Gray Heron, Siberian Cranes or Greater Flamingo, etc.

FAQs on Migratory Birds

What are the Major Reasons For Bird Migration?

There can be several reasons for the birds' migration. Food is one of the major reasons for their migration. If they all stay at one place then food will be exhausted & scarce during the breeding time. Thus, they migrate to food-abundant areas. During the breeding season, the depletion of food will not only affect the adult birds but also attract a lot of predators because they become an easy meal for them. 

Birds usually migrate for their family or we can say for healthy breeding for which they require healthy conditions for raising their offspring. Another reason can be a change in the climatic or weather conditions of the locations and if any change occurs in these conditions can cause their migration because it makes it difficult for them to survive in these harsh conditions. On the other hand, they also can migrate to save themselves and their offspring from predators and various diseases. They usually migrate to places where they are safe and are inaccessible to predators.

What is Latitudinal Migration?

There are different types of bird migration. In latitudinal migration,  birds migrate from north to south (or south to north) between their breeding and non-breeding area. Some migrant species breed in temperate North America and migrate to tropical America.

What is Altitudinal Migration?

Altitudinal migration is not as common as longitudinal Migration but has the same principle. Unlike the latitudinal migration when the migrants cover long distances, altitudinal migrants cover short distances from montane regions to lower elevations outside of their breeding season. This is usually triggered by food abundance in these areas.

How do birds navigate during migration?

The secrets of amazing navigation skills of birds aren't fully understood, they combine several different types of senses during the journey to navigate. They use information from the sun, the stars, and by sensing the earth’s magnetic field they are able to navigate easily. Birds get information from the position of the setting sun and from landmarks seen during the day. There is even proven evidence that sense of smell plays a role, at least for homing pigeons.

Biology • Class 11

World Migratory Bird Day

4 Of The Most Beautiful Migratory Birds That Visit India Every Year

By Aishwarya Das Pattnaik

World Migratory Bird Day is a global celebration dedicated to raising awareness of birds and nature. 🕊️🐧🦅

This year's theme of " Sing, Fly, Soar – Like a Bird !" is a way to inspire and reconnect people back to nature by actively listening to and watching birds - wherever they are.

Birds can be spotted everywhere. From soaring on high peaked icy mountain caps to marshy wetlands, forests, grasslands and even our balconies – their energetic presence is felt like no other animal. This year, because of the COVID-19 pandemic, bird watchers are documenting migratory birds from their backyards too!

These migratory feathered visitors not only connect all these diverse habitats, but they restore our connection with our biodiverse planet and with themselves too.

Many migratory birds take excruciating journeys by flying thousands of kilometres while some elevate to just a few hundred feet. Birds migrate from one region to another to avoid harsh climate, search for food, and find nesting locations.

Catching a glimpse of them is a dream for every avid bird watcher.

But, it can be the same for you too.

A birder's guide

Every year birds from 29 countries take a flight to India. We can spot large incoming flocks during September-October, marking the beginning of migration .

A whopping number of approximately 1,349 species of birds have been recorded as of 2019. 78 are endemic to the country, and 212 species are globally threatened, according to the Government of India.

Jacobin Cuckoo - Harbinger of the monsoon rains Famously known as Piped Cuckoo or Chatak, these species are of culturally great significance to many in our country. Its presence is considered auspicious as they welcome the onset of monsoons in India. These crest-headed species with a black and white plumage belong to the cuckoo order of birds found in Africa and Asia. Known to be partially migratory, they can be seen in Southern India year-round. However, this species migrates from the eastern parts of Africa during summers to North and Central India. In North India, they breed from June to August, and in South Nilgiris, they breed from January to March.

Indian Pitta: The six o’clock bird The Indian Pitta is a sight to watch! Colourful as they appear, they sing the chirpiest bird songs and have a loud whistle call. It has a unique stubby tail and a body filled with different shades of cerulean blue feathers. These dawn to dusk callers often heard during sunrise and sunset (around 6 o'clock) can be listened to the most during its breeding season.    The species is termed as a "local migrant" – they fly within the Indian borders. During summers, they breed in India's Central and Northern parts while migrating to the south in winters.

Blue-tailed Bee Eater: The real Angry Birds It's obvious where the Blue-tailed bee-eaters get their names. These skilled bee hunters seal any deal with one another with a bee! The slender boned species belong to the Meropidae family and are widely distributed across South and Southeast Asia. They make their way to North India and the Himalayan states during the summer season. These birds catch their prey in the open air, returning to a perch with it. They do not eat the insect or bee directly but rather toss and swallow it.

Steppe Eagle: The majestic national bird of Egypt The Steppe Eagle is a large bird with strongly hooked bills and remarkably well-feathered legs. Classified as an 'endangered' species, these long-winged beasts of the skies are believed to be the second-largest long-distance migratory birds. It has an extensive breeding range from Southeast Europe, Central Asia, Russia, northern Kazakhstan to west Manchuria, north Tibet and Mongolia. From October onwards, they move south to undertake their winter sojourn to the Indian sub-continents. The national bird of Egypt, they can be spotted mainly in North India and the Himalayan ranges. But, last year, a lone migratory Steppe Eagle was sighted in a paddy field at Velagaleru near Vijayawada – a relatively rare occurrence!

Importance of migratory birds:

Presence of migratory birds is a positive indicator of a healthy ecosystem. They have various indispensable roles in the places they travel through and areas they reside. Some of their key contributions include, controlling pests by devouring insects and other organisms that harm crops, dispersing seeds, and playing a critical role in pollination.

How are migratory birds passage impacted?

The most critical step for protecting migratory species is to identify their stopover sites and wintering grounds. With rising habitat loss, Arpit mentions that solid engagement with communities is essential to safeguard these key habitats for our winged friends.

Enjoy more images of migratory birds found in India

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Open Access

Peer-reviewed

Research Article

Modeling the Distribution of Migratory Bird Stopovers to Inform Landscape-Scale Siting of Wind Development

* E-mail: [email protected]

Affiliation The Nature Conservancy, Wyoming Chapter, Lander, Wyoming, United States of America

Affiliation Wyoming Natural Diversity Database, University of Wyoming, Laramie, Wyoming, United States of America

• Amy Pocewicz, 
• Wendy A. Estes-Zumpf, 
• Mark D. Andersen, 
• Holly E. Copeland, 
• Douglas A. Keinath, 
• Hannah R. Griscom

• Published: October 2, 2013
• https://doi.org/10.1371/journal.pone.0075363
• Reader Comments

Conservation of migratory birds requires understanding the distribution of and potential threats to their migratory habitats. However, although migratory birds are protected under international treaties, few maps have been available to represent migration at a landscape scale useful to target conservation efforts or inform the siting of wind energy developments that may affect migratory birds. To fill this gap, we developed models that predict where four groups of birds concentrate or stopover during their migration through the state of Wyoming, USA: raptors, wetland, riparian and sparse grassland birds. The models were based on existing literature and expert knowledge concerning bird migration behavior and ecology and validated using expert ratings and known occurrences. There was significant agreement between migratory occurrence data and migration models for all groups except raptors, and all models ranked well with experts. We measured the overlap between the migration concentration models and a predictive model of wind energy development to assess the potential exposure of migratory birds to wind development and illustrate the utility of migratory concentration models for landscape-scale planning. Wind development potential is high across 15% of Wyoming, and 73% of this high potential area intersects important migration concentration areas. From 5.2% to 18.8% of each group’s important migration areas was represented within this high wind potential area, with the highest exposures for sparse grassland birds and the lowest for riparian birds. Our approach could be replicated elsewhere to fill critical data gaps and better inform conservation priorities and landscape-scale planning for migratory birds.

Citation: Pocewicz A, Estes-Zumpf WA, Andersen MD, Copeland HE, Keinath DA, Griscom HR (2013) Modeling the Distribution of Migratory Bird Stopovers to Inform Landscape-Scale Siting of Wind Development. PLoS ONE 8(10): e75363. https://doi.org/10.1371/journal.pone.0075363

Editor: Claudia Mettke-Hofmann, Liverpool John Moores University, United Kingdom

Received: April 28, 2013; Accepted: August 13, 2013; Published: October 2, 2013

Copyright: © 2013 Pocewicz et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: This study was funded by a grant from the Mayer and Morris Kaplan Family Foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Introduction

Conservation of migratory birds requires an understanding of habitat, behavior and threats faced by birds during breeding, wintering, and migration. Migration is the most poorly understood of these annual activities, and of particular importance is understanding the distribution of stopovers and pathways used by migrating birds [1] . Recent technological advances, including telemetry devices, radar, stable isotope analysis, and genetic markers, permit the tracking of birds during migration [2] . Geographic Information System (GIS) modeling is also being used increasingly across large regions to evaluate conservation strategies and assess risks to migrating birds [3] , [4] .

One risk to migrating birds is wind energy development, which is expected to increase substantially in the United States in the coming decades due to evolving policies aimed at increasing renewable energy production [5] – [7] . Wind development can negatively impact birds through direct mortality from turbine collisions, avoidance behavior, and indirect effects of habitat fragmentation [8] – [12] . The U.S. Fish and Wildlife Service, Partners in Flight, The Wildlife Society, and the American Bird Conservancy, among others, have raised concerns about the long-term impacts of wind energy on bird populations [9] , [13] . Mortality related to wind turbines could have especially great effects on declining species and long-lived species with low fecundity, such as raptors [14] .

Wind development impacts to migratory birds may be reduced if facilities avoid major migration stopovers and flyways or if turbine operations are reduced in these areas during peak migration [13] , [15] . However, the lack of information on the distribution of migratory concentration areas, and their overlap with wind energy resources, impedes conservation and proactive development planning [16] . Several studies have examined bird migration patterns and modeled stopovers and pathways in the eastern U.S. [3] , [4] , but much less is known about migration patterns in the western U.S. [17] , especially in the Rocky Mountains. Limited regional information exists as incidental sightings [18] , migration counts [19] , [20] , local or species specific research reports, e.g. [21] – [23] , and expert knowledge, but has not been synthesized.

We developed a deductive modeling approach based on a synthesis of literature and expert knowledge concerning bird migration, and represented through GIS datasets, to map migratory concentration areas across the state of Wyoming. We produced deductive models due to concerns regarding the quality and quantity of available occurrence data needed to generate reliable inductive models. Deductive models, often referred to as habitat suitability models, are based on knowledge from literature or experts that is represented directly via environmental variables, while inductive models relate environmental variables to species occurrence locations using statistical algorithms [24] . Researchers have begun generating nationwide models depicting species’ distributions throughout the year based on inductive modeling of occurrences [25] ; these efforts contribute significantly to our understanding of migration timing at broad scales. However, these efforts are limited by a lack of occurrence data from migration seasons for sparsely populated areas like Wyoming, and by the inclusion of only a few general predictors of distribution. We were able to identify, create, and tune model parameter layers (e.g., topographic leading lines) that represent important drivers of local migratory concentration. It will likely be many years before there is sufficient occurrence data to model migration concentration across Wyoming using inductive methods, and there is an urgent need for these models now.

The goals of our research were to 1) create and test spatially-explicit models representing migratory concentration areas for four functional bird groups and 2) assess the potential exposure of bird migration concentration areas to future wind energy development, to illustrate the utility of migration concentration models for landscape-scale planning. Wyoming has abundant wildlife resources, relatively intact ecosystems, and also some of the nation’s best wind energy resources. Wyoming currently has nearly 1000 wind turbines, and an additional 5000 turbines could be installed during the next 20 years [26] . Wind development has the potential to impact bird populations within the state and beyond its borders, if development occurs without regard for migrating birds. The migratory concentration maps presented here provide preliminary data to companies and land management agencies planning for wind development in Wyoming, and our methods could be replicated in other places where maps of migration hotspots are lacking.

Our study area encompasses the state of Wyoming, which lies on the boundary between the Central and Pacific Flyways ( Figure 1 ). Wyoming’s several large mountain ranges are dominated by conifer forests and are the source of several major rivers. Sagebrush and other shrublands dominate the inter-mountain basins, and grasslands are found in the lowest elevations of eastern Wyoming.

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(A) Wyoming lies on the western edge of the Central Flyway and eastern edge of the Pacific flyway. Flyways are identified in varying shades of gray. (B) Key features influencing bird migration include topography (shown in brown shading) and major rivers (shown in blue). County boundaries are displayed for reference.

https://doi.org/10.1371/journal.pone.0075363.g001

Wyoming is the least populated state in the United States. Lands are primarily used for livestock grazing in the western two thirds of the state and for both crop production and grazing in the eastern third. Despite Wyoming’s low human population, much of the state is experiencing energy development [27] . In addition to extraction of fossil fuels, including coal, oil, and natural gas, Wyoming has received considerable interest in its wind energy potential recently due to wind resources that rank it 8 th out of the 50 U.S. states [28] .

Modeling Bird Migratory Concentration

We created models representing where four functional groups of birds concentrate in Wyoming during their migration. We focused primarily on groups of birds species that concentrate at stopovers during migration to stage, forage or rest [29] , because migrants that are concentrated in large densities are at greater risk for collisions with wind turbines [15] , [30] . We used functional groups having similar migration behaviors, because insufficient migratory behavior information and occurrence data are available for many individual species. The four functional groups were wetland birds, riparian birds, raptors and sparse grassland birds, and species represented by each group are listed in Tables 1 and 2 . Sparse grassland birds are those species that use sparsely-vegetated grasslands. All groups are comprised of species that concentrate during migration, except sparse grassland birds, which were included because many of these species are declining. We modeled spring migration patterns for wetland and riparian birds and fall migration patterns for raptors, because migration is most concentrated during these seasons for each group. We did not model both spring and fall migration for these groups, because we were most interested in when birds are most concentrated. For sparse grassland birds, we modeled spring migration because preliminary analysis indicated that our model was more indicative of spring than fall migrant distribution. We initially considered forest and shrubland birds but did not include them because they concentrate less during migration and may be partly represented by the riparian group, because they often follow riparian corridors during migration [17] , [21] , [22] , [31] .

https://doi.org/10.1371/journal.pone.0075363.t001

https://doi.org/10.1371/journal.pone.0075363.t002

The conceptual models were represented spatially using raster-based GIS data, at 90-m resolution, through commonly-applied methods for integrating multiple factors into suitability maps [77] . Raster cells in datasets representing factors (e.g., streams) were scaled from 0 to 1, where 0 = no importance for migration, 0.25 = low importance, 0.5 = medium importance, and 1 = high importance. Raster cells in datasets representing modifiers of factors (e.g., orientation of streams) were assigned values ranging from 0 to 2, where values of 0 reduced the importance of associated factors to zero, values of 1 left associated factor values unchanged, and values of 2 doubled the importance of associated factors in those locations. After multiplication by one or more modifiers, the value of an individual factor was normalized to range from 0 to 1. This normalization assured that each factor had the same relative importance in the model. However, for factors identified as being of greater importance than other factors, we multiplied that factor by a weight greater than 1 [77] . Finally, the individual normalized weighted or unweighted factors were added to cumulatively represent factors important to migration concentration. The final MIS values were normalized to range from 0 to 1.

More than fifty Wyoming bird experts, who represented state and federal agencies, non-profit groups, and the University of Wyoming, were identified and invited to provide input on a an earlier version of the models presented in this paper. We received feedback and suggestions from more than 25 of these experts through in-person and phone meetings and written comments, and we made modifications to the models based on this input.

Wetland bird migration concentration.

The wetland bird group includes waterfowl as well as birds that feed by wading in shallow water and mudflats along the shore of wetlands (hereafter “shorebirds”; Table 1 ). We identified that streams, wetland density, wetland size, and forage availability are important factors for wetland bird spring migration concentration, and that the importance of these factors varies with elevation, proximity to rivers, and location within or outside the Central Flyway. The model was implemented as: w 1 *(Streams)+w 2 *(Wetland density * Elevation * Proximity to river * Flyway location )+w 3 *(Wetland size * Elevation * Proximity to river * Flyway location )+w 4 *(Forage availability * Proximity to river )+w 5 *(Take-off/approach buffer), where modifiers are italicized and w 1 , w 3 , w 4 , w 5  = 1 and w 2  = 3. Value ranges of model factors and modifiers are described in Table 3 .

https://doi.org/10.1371/journal.pone.0075363.t003

Wetland birds generally migrate at night, stopping and feeding during the day. Wetland birds are among the species that attain the highest altitudes during migration, and are often capable of flying long distances (>3,200 km) non-stop unless forced by exhaustion or weather to land [32] . Wetland birds often use rivers to navigate during migration [32] – [34] . Rivers in the arid west may not only serve as navigation aids, but also a source of reliable stopover habitat in the form of reservoirs, off-channel wetlands, and agricultural fields [33] , [35] , [36] . Stopover habitat is typically similar to breeding habitat for a given species, though a wider range of resources may be used during migration [37] – [41] . Thus, stopover habitat for wetland birds includes marshes, wetlands, lakes, reservoirs, and other water bodies, e.g. [32] , [33] , [41] – [49] . In Wyoming, wetland birds concentrate in locations where wetlands are clustered in high densities. We weighted wetland density higher than other factors because its importance was emphasized by experts. This importance is also supported by the establishment of hundreds of national wildlife refuges for waterfowl encompassing important wetland clusters, and the use of these and similar wetland preserves by migrating waterfowl and shorebirds [32] , [46] , [50] . Larger lakes and wetlands can support large groups of migrating birds and provide safety from predators and are valuable even if not part of a wetland cluster. Heavy wing-loading in many wetland bird species can result in slow climbing rates [29] , [32] , placing them at risk of collisions with turbines during approach and take-off at stopover and foraging sites [30] , [51] . We buffered wetlands and streams by 1 km to account for long approach/take-off distances needed by many wetland birds [8] . Agricultural lands can also provide food for migrating birds at stopover sites [52] . Many species of ducks, geese, and gulls forage in agricultural areas with grain crops [32] , [53] – [56] , and some wetland birds forage in irrigated pasture or hay meadows [47] , [48] .

The importance of wetlands and foraging areas varies with location. Wetlands and foraging areas closer to major streams are more likely to be used because of the tendency of wetland birds to travel along rivers. Wetland birds are unlikely to use high elevation wetlands during spring migration, because they may still be covered with snow or ice. We reduced the importance value for clusters of wetlands when they were located at high elevations that would likely be under snow cover during spring migration, using an elevation cutoff suggested by wetland bird experts. Eastern Wyoming overlaps the Central Flyway, a major migration route for waterfowl, and thus tends to have higher concentrations of ducks and geese than the western portion of the state.

Riparian bird migration concentration.

The riparian bird group includes cuckoos and certain species of songbirds and flycatchers ( Table 1 ). However, the model will over-predict migration habitat for birds restricted to mature cottonwood forests, such as the Yellow-billed Cuckoo ( Coccyzus americanus ). Our riparian model may also represent some forest or shrubland migrants, which often follow riparian corridors [17] , [21] , [22] , [31] . We identified that streams and wetland density are important factors for riparian bird spring migration concentration, and that the importance of these factors varies with stream orientation, willow and cottonwood abundance, riparian structural diversity, elevation, and proximity to rivers. The model was implemented as: w 1 *(Streams * Stream orientation * Cottonwood abundance * Willow abundance * Riparian structural diversity )+w 2 *(Wetland density * Elevation * Proximity to river ), where modifiers are italicized and w 1  = 2 and w 2  = 1. Value ranges of model factors and modifiers are described in Table 4 .

https://doi.org/10.1371/journal.pone.0075363.t004

Riparian migrants concentrate along perennial streams where well-developed and structurally-diverse riparian trees and shrubs are present [17] , [21] , [22] , [57] , [58] . Riparian migrants are most likely to use larger, north-south oriented streams to guide migration [17] , [58] , and cottonwood and willow-dominated riparian areas are used more frequently than other vegetation types [17] . Isolated oases of riparian habitat are often found around large permanent wetlands and are important to riparian migrants, especially in arid landscapes like much of Wyoming [17] , [58] ; riparian birds will concentrate at permanent wetlands because of their riparian vegetation. Since riparian birds concentrate along large perennial streams, wetlands closer to these streams are more likely to be encountered and used as stopover habitat. Migrating birds will use all riparian areas in xeric landscapes, but lower elevation riparian corridors tend to be used by a greater number of species [22] , [59] . We used stream order as a surrogate for an elevation cutoff for streams, to avoid excluding large streams that occur at high elevations. Some migrants may use different routes in spring and fall, with lower elevation riparian corridors used more heavily in spring, when higher elevation riparian and forested areas are still snow-covered with fewer food resources [17] , [60] , [61] . We reduced the importance of wetlands when they were located at high elevations that would likely be under snow cover during spring migration. The stream factor was given twice the weight of the wetland density factor in our model, to reflect the especially high importance of streams and riparian areas to this group of birds [17] , [21] , [58] .

Raptor migration concentration.

The raptor group includes diurnal birds of prey ( Table 2 ). We identified that topographic features, updrafts, thermals, and streams are important factors for raptor fall migration concentration, and that the importance of these factors varies with topography and stream orientation and cottonwood abundance along streams. The model was implemented as: w 1 *(Topography * Topography orientation )+w 2 *(Updrafts)+w 3 *(Thermal formation)+w 4 *(Streams * Stream orientation * Cottonwood abundance ), where modifiers are italicized and w 1 through w 4  = 1. Value ranges of model factors and modifiers are described in Table 5 .

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Unlike many other migrants, most raptors do not maintain high altitudes during migration. Instead, they conserve energy by gaining lift from updrafts and thermals and gliding long distances, slowing losing altitude, to the next updraft or thermal [29] , [62] , [63] . Therefore, instead of concentrating at stopovers, raptors concentrate in areas that provide the best updrafts and thermals, especially during fall migration. Ridges and mountain ranges oriented perpendicular to prevailing winds produce the strongest updrafts. Although some ridges consistently provide strong updrafts, the location of updrafts can vary daily with local wind and weather conditions. As a result, when updrafts are not available, raptors will adjust their migration routes to take advantage of thermals, which form over surfaces that heat up the air faster (e.g. rock, sand, bare ground, pavement) [62] , [63] .

Prominent landscape features, including streams and topographic features such as tall ridges, provide leading lines that can guide raptor movements and concentrate migrants [62] , [64] . Leading lines that are oriented in the general direction of migration (north/south in Wyoming) are of particular importance, as are stream leading lines that include perching locations such as cottonwood trees. Some raptor species avoid crossing inhospitable habitat, such as deserts and large water bodies, and divert travel around the edges of these features [62] . Both leading lines and diversion lines concentrate migrating raptors, but we focused on leading lines because Wyoming lacks substantial diversion lines.

Raptor species likely not well-represented by this model include the Prairie Falcon ( Falco mexicanus ) and Peregrine Falcon ( Falco peregrinus ); they migrate at much higher altitudes and have dispersed and unique migration patterns [65] – [67] . Bald Eagle ( Haliaeetus leucocephalus ) [23] , Ferruginous Hawk ( Buteo regalis ) [68] , and Swainson’s Hawk ( Buteo swainsoni ) [69] migration patterns also do not fit this raptor model due to specific habitat needs.

Sparse grassland bird migration concentration.

The sparse grassland group includes species that use sparsely-vegetated grasslands or areas dominated by prairie dog colonies ( Table 2 ). We identified that grassland land cover types and presence of prairie dogs are important factors for sparse grassland migration concentration, and that grasslands having more bare ground are preferred. The model was implemented as: w 1 *(Land cover * Bare ground cover )+w 2 *(Prairie dog occurrence likelihood), where modifiers are italicized and w 1 and w 2  = 1. Value ranges of model factors and modifiers are described in Table 6 .

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In Wyoming, the sparsely-vegetated grasslands used by these birds during migration are relatively widespread. Therefore, in Wyoming, this group of migrants tends to exhibit a more dispersed pattern during migration than other avian species. This model is based largely on broad habitat requirements, because specific information on migration behavior for this group was generally lacking. Sparse grassland birds prefer short-grass and mixed-grass prairie and/or low shrublands with a high bare-ground component [68] , [70] – [73] . These species will often use heavily grazed, previously disturbed, tilled, and even somewhat degraded landscapes. Many sparse grassland birds, such as the Mountain Plover ( Charadrius montanus ), are often associated with prairie dog ( Cynomys spp.) colonies because of the close-cropped grass and high bare-ground components they provide [73] – [76] . Prairie dog colonies also provide a diversity of small mammal and avian prey for raptors, such as the Ferruginous Hawk.

Model Validation

The final predictive maps were validated using expert opinion and available observation data. Expert validation was completed through a web-based review of the final maps by statewide bird experts. We invited a larger group of experts to participate than for draft model feedback, but the majority of respondents had also been engaged in the first process. We asked experts to provide their assessment of each model on a 5-point Likert-type scale [78] that included rating selections of very poor (−1), poor (−0.5), okay (0), good (0.5), and very good (1) and to rate their level of expertise for each bird group on a 5-point Likert-type scale that included rating selections of very low (1), low (1.25), moderate (1.5), high (1.75), and expert (2). We multiplied the two rating values to weight each model rating by the reviewer’s level of expertise and averaged these expertise-adjusted scores for each model to obtain a final weighted-average score. Scores below zero indicated a poor model, scores of zero indicated an average model, and scores greater than 0 indicated a good model.

The observation-based validation used an occurrence dataset assembled from the Wyoming Natural Diversity Database ( http://www.uwyo.edu/wyndd ) and eBird [18] for each species represented by the models for the time period representing the majority of their typical spring or fall migration through Wyoming. From eBird, data were included only from exhaustive area, random, stationary and traveling counts. Migration time periods were extrapolated from species accounts in Birds of North America Online ( http://bna.birds.cornell.edu/bna/species/ ), eBird [18] , and Birds of Wyoming [79] ( Tables 1 and 2 ). We removed occurrences of questionable quality or with a spatial accuracy of less than 400 m. Next, for each bird group, we removed points that were closer than 800 m to a point deemed to be of better quality, based on mapping precision, recentness, and certainty of identification. Filtered occurrence points were subsampled to balance contributions of individual species, to minimize bias of validation statistics towards particular species with more occurrences, while still providing a minimum of 50 points for validation that were well-distributed across Wyoming. For each bird group, validation points were selected at random from filtered occurrences, stratified by species (see Tables 1 and 2 ). Up to 10 points per species were selected, where available.

We applied the Boyce index to measure observed versus expected occurrence, using the selected validation data points and binned versions of the models. Bins were created so that each bin contained approximately the same number of validation points. The Boyce index is a Spearman rank correlation between the area-adjusted frequency of validation points falling within a bin and the associated bin’s rank [80] . The validation points were ranked based on their predicted concentration score, and we chose the midpoints of the scores above and below the bin breaks as binning thresholds for the raster models. The Boyce index varies between −1 (counter prediction) and 1 (positive prediction), with values close to zero indicating that the model does not differ from a random model. Data were partitioned into 10 bins for each group, based on the model value assigned to the validation points, with exception of riparian birds, which had 8 bins. The bins in the riparian model were more limited in number due to a large proportion of raster cells with a predicted concentration score of zero and thus a large number of points occurring in the first bin.

Model Sensitivity and Uncertainty

We completed a sensitivity analysis of each of the four models to characterize the uncertainty associated with each model and describe how much the output of each model changed based on the contribution of each factor, modifier, or weight. We dropped each factor, modifier or weight one at a time from each model, and described the subsequent change in three ways. First, for each raster cell we calculated the percent difference between the partial model (missing one term) and the full model (all terms included), as the absolute value of the full model minus the partial model, divided by the full model. For each partial-model versus full-model combination, we calculated the mean and standard deviation of the percent difference across the study area. Second, we classified the full model raster and each partial model raster into 5-quantiles and, for each partial-model versus full-model combination, we tallied the number of raster cells having class agreement using the crosstab function in the R [81] raster package [82] . This resulted in an error matrix from which we calculated classification accuracy [83] , the percentage of raster cells in each partial model that were classed in the same bin as the full model. Finally, to visualize potential spatial pattern in uncertainty, for each cell in our study area we calculated the mean of the percent difference values across all partial-model versus full-model combinations.

Exposure of Migrants to Wind Energy Development

To assess the potential exposure of migratory birds to wind energy development, we measured the overlap between the maps of migration concentration and a predictive model of wind energy development potential. Our intent was to provide a coarse-scale analysis of where conflicts may exist with future wind development and to illustrate the utility of migration concentration models for landscape-scale planning. For these reasons, we used wind development potential rather limiting the analysis prescriptively to specific proposed wind farm projects. We created a predictive model of Wyoming wind energy development potential that incorporated wind resource potential, near-term development indicators and current development restrictions [84] . First, we fit a predictive model using maximum entropy methods [85] , [86] and Maxent® software version 3.3.3e. Maxent uses presence-only data, which was appropriate for this dataset because we did not have true absence data representing where turbines could not feasibly be built. The model used existing wind turbines as the response variable [87] . Predictor variables were the average 50-m wind resource potential [88] , percent slope, and topographic position (i.e., ridge, valley) [89] , because these factors influence the quality of the wind resource or feasibility of turbine construction (see [84] for details). We used a randomly-selected 67% of wind farms (643 turbines, 32 farms) to train the model and 33% to test the model (319 turbines, 8 farms), including all turbines within individual wind farms as either training or test data to avoid spatial autocorrelation. The model performed well, with a test area under the receiver operating characteristic curve (ROC AUC) of 0.91. A ROC AUC value of 0.5 indicates model performance no better than chance and values above 0.5 indicate increasingly strong classification to an upper limit of 1 [90] .

The Maxent® model represented the quality of wind resources but did not prioritize where development would most likely occur in the near term. Therefore, we adjusted the model results using short-term development indicators, including density of existing meteorological towers used to test wind speeds, distance to proposed transmission lines, proposed wind farm boundaries and land tenure [84] . Finally, we excluded locations where development was precluded due to legal or operational constraints, including protected lands (e.g. wilderness areas, conservation easements), airport runway space, urban areas, mountainous areas above 2743-m, and open water [84] . The adjusted model had a Boyce index of 0.89 (p = 0.001). A GIS version of the wind development model is available for download through the Wyoming Geographic Information Science Center (WYGISC).

We combined the wind potential dataset with each of the four migration model results to evaluate how much exposure migratory birds may have to future wind development. To understand spatial patterns in exposure, we first classified each of the five datasets into five quantile bins of potential for bird migration or wind development. This step was necessary to make the values comparable among the various models; while all models ranged from 0 to 1, the absolute values were scaled relative to each individual model. Values of 1, 0.75, 0.5, 0.25, and 0 were assigned to the quantile classes, where 1 corresponded to the quantile including the highest 20% of the data (i.e., very high). The wind potential and bird migration rasters with these new values were then multiplied, separately for each bird group. Where wind development potential was high (0.75) and migratory concentration was high (0.75), we assumed that exposure of birds to development would also be high (result = 0.5625) and that where wind development potential was low (0.25) and migratory concentration was low (0.25), exposure of birds would be low (result = 0.125). Therefore, we developed the following classes to reflect exposure level: very high (>0.75), high (0.56–0.75), moderate (0.26–0.559), low (0.1–0.259), or very low (<0.1). To spatially represent uncertainty in exposure, we determined exposure for each of the partial models and then calculated the standard deviation of the mean exposure across the full and partial models for each bird group.

Additionally, we focused on those areas with the highest likelihood for potential wind development – the top two quantile classes of high and very high – and summarized 1) the percentage of the top two migration quantiles for each bird group overlapping with these areas and 2) the percentage of the top two wind potential quantiles overlapping with the most important concentration areas for each bird group. We determined these percentages for the full models and also calculated the mean and 95% confidence interval across the full and partial models. Important migration concentration areas may not overlap spatially among the four bird groups, so we also combined the top two quantiles for each bird group into one raster representing cumulative migration concentration to generate the percentages described above.

The results for each model are presented as five quantiles in predictive maps, where the highest 20% of values are displayed as raster cells that are of greater importance for migration concentration than 80% of all cell locations ( Figure 2 ). GIS versions of the migration models are available for download through WYGISC.

Continuous modeled values were binned into five quantiles representing relative importance for migration concentration. Darker colors represent areas with greater importance, where >80% represents areas more important than those found across 80% of the state. The models represent (A) Raptor fall migration concentration (B) Wetland bird spring migration concentration (C) Riparian bird spring migration concentration and (D) Sparse grassland bird migration concentration.

https://doi.org/10.1371/journal.pone.0075363.g002

Model Validation and Sensitivity

The expert validation survey was completed by 13 (28%) of the invited experts. An additional seven experts provided comments but did not rate the models. The overall model rating was “very good” for wetland (score = 0.88, n = 12) and riparian birds (score = 0.97, n = 11) and “good” for raptors (score = 0.45, n = 10) and sparse grassland birds (score = 0.69, n = 11). Qualitative comments were consistent with the aforementioned ratings, with experts providing the most favorable comments about the wetland and riparian bird models and raising more concerns related to the raptor and sparse grassland bird models. We found significant agreement between species occurrence data and the migration models for wetland (p = <0.0001, Boyce index = 0.952), riparian (p = 0.001, Boyce index = 0.976), and sparse grassland bird migration (p = <0.001, Boyce index = 0.903) ( Figure 3 ). There was no agreement between occurrence data and the raptor migration model (p = 0.467, Boyce index = −0.030) ( Figure 3 ).

The observed to expected ratio in each quantile bin used to calculate the Boyce index for validation of migration models for (A) wetland birds, (B) riparian birds, (C) raptors and (D) sparse grassland birds. Models with a perfect fit show a monotonic increase as bin numbers increase, which is best illustrated in panel A.

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Model were most sensitive to the removal of base factors, such as streams for riparian birds, wetland density for wetland birds, and land cover for grassland birds ( Table 7 ). The raptor migration model was most sensitive to the updraft and thermal formation factors ( Table 7 ). Overall, uncertainty was lowest for the wetland bird model and highest for the sparse grassland bird model ( Figure 4a, d ). Across models, uncertainty tended to be greatest at higher elevations ( Figure 4a, b, d ).

These values represent the average percent difference of the partial sensitivity models (with one variable dropped at a time) from the full models. Locations with higher values are locations where the various versions of the model had the greatest differences, for A) wetland birds, B) riparian birds, C) raptors, and D) sparse grassland birds.

https://doi.org/10.1371/journal.pone.0075363.g004

https://doi.org/10.1371/journal.pone.0075363.t007

The potential for new wind development is highest in eastern and southeastern Wyoming ( Figure 5 ), and obviously exposure of migration concentration areas is also greatest within these areas of the state ( Figure 6 ). The spatial patterns in exposure varied among the four bird groups. For example, the highest exposures for grassland birds were mainly clustered in southeast Wyoming ( Figure 6g ), while high exposures for raptors were well-distributed along ridges throughout areas with high wind development potential ( Figure 6e ). Uncertainty in exposure to wind development ranged up to a standard deviation of 0.35 for wetland and riparian birds and 0.45 for raptors and sparse grassland birds ( Figure 6 ), on an exposure scale of 0 to 1 ( Figure 6 ).

Continuous modeled values were binned into five quantiles representing relative development potential and are followed by the percentage of the state’s area included in that bin.

https://doi.org/10.1371/journal.pone.0075363.g005

Exposure classes in each map are followed by the percent of the state occurring in that class. Uncertainty in exposure is represented by the standard deviation in exposure among the full and partial models for each bird group and is shown for (B) wetland birds, (D) riparian birds, (F) raptors, and (H) sparse grassland birds. Standard deviation is relative to an exposure value range of 0 to 1. Standard deviation classes in each map are followed by the percent of the state occurring in that class.

https://doi.org/10.1371/journal.pone.0075363.g006

Wind development potential was categorized as high or very high across 14.7% of Wyoming ( Figure 5 ). Important migratory concentration areas for each of the four bird groups were exposed to only portions of this area of high development potential ( Figure 6 ; Table 8 ). Sparse grassland bird important migration areas had the highest percent overlap with high wind potential areas and riparian birds the lowest ( Table 8 ). Seventy-three percent of the high wind potential area overlaps with important migration areas, when considered across all bird groups ( Table 8 ). This overlap is less for each individual group, and the individual values do not sum to the total because there is spatial overlap among migration areas for the various groups ( Table 8 ). The 73% of the wind potential area that overlaps with important migration areas corresponds with 13.2% of the important migration areas, across all four groups ( Table 8 ). Uncertainty in the two calculated percentages, represented by 95% confidence intervals, was low for all groups except sparse grassland birds ( Table 8 ).

https://doi.org/10.1371/journal.pone.0075363.t008

Models of migratory concentration for wetland, riparian, and sparse grassland birds were consistently rated as accurate representations based on validation from experts and existing datasets. These models provide a much needed initial assessment to highlight important resources for migrants where little is currently known, as is the case in Wyoming. The model set can be updated as new information on migration patterns or improved spatial data layers become available, and can be expanded to predict concentrations for other groups of birds or for individual species. Our approach could be replicated elsewhere to fill critical data gaps for migratory birds.

Our migratory concentration models can be used to inform siting of wind developments and identify where mitigation may be needed. These models are well-suited for the preliminary site evaluations recommended by the U.S. Fish and Wildlife Service (USFWS) to identify possible conflicts with habitats or species of concern at a landscape scale [13] . The USFWS implements the Migratory Bird Treaty Act, which prohibits the killing or harming of migratory birds, and wind energy developers are required to comply with this statute on both public and private lands. Our models could also be used by federal land management agencies, such as the Bureau of Land Management, to support regional planning for wind development on public lands. Preliminary site evaluations can identify where development might be avoided, and our models could also inform other stages of the mitigation hierarchy, including identifying potential mitigation offset opportunities [91] – where some important migration areas might be protected from development following impacts to other important migration areas. In locations where migratory birds concentrate and wind development cannot be avoided, a number of onsite mitigation techniques can be used to minimize risk to birds [8] , [13] , [15] . First, pre-construction surveys characterize bird use of project areas and aid in turbine placement that minimizes contact with birds and other wildlife. Second, minimal use of red or white flashing lights on wind turbines and associated infrastructure is much less likely to ‘draw’ migrating birds into the rotor-swept zone. Also, power transmission lines pose collision threats to migrating birds and should be minimized and buried when possible. Finally, post-construction surveys can help identify high mortality areas where additional mitigation measures may be needed, such as turning off high-risk turbines during peak migration times [15] . Our landscape-scale models are not a substitute for pre- or post-construction studies within project areas; mortality rates may be site-specific and depend upon the siting of individual turbines [92] .

The amount and location of exposure of migratory birds to wind development differed among the four groups of migrants. Not surprisingly, we noted the greatest potential exposure for sparse grassland birds, which use grasslands in the southeastern portion of Wyoming that havesome of the best wind resources. There was also the greatest uncertainty in exposure for sparse grassland birds, as that model relied heavily on grassland cover types, that when removed, shifted the important migration areas outside the geographic extent where wind development is anticipated. For sparse grassland birds, we expect that the overlap estimates with wind potential that are based on the full model including all three variables is the most accurate, due to the limited number of model factors. The raptor model performed poorly in validation against existing occurrence data, but we retained the model in the wind exposure analysis because it was rated well by experts and currently provides the only available spatially-synthesized information for raptor migration in Wyoming. The amount of exposure for raptors showed little variability among the full and partial models, suggesting that the model may offer a reasonable best estimate of exposure to wind development. Potential conflict was most limited for riparian birds, which are the most concentrated of the migrants, clustered primarily along valleys that generally have lower wind development potential. As a percentage of the total area of important migration concentration areas, overlap with the highest wind development potential areas was relatively low, ranging from 5.2 to 18.8%. However, impacts to these small relative percentages of the migration concentration areas could have a proportionally larger population impact. We expect that 60% or more of migrating individuals from each of these functional bird groups may be using the areas that we identified as most important (i.e., the top two model quantiles).

Our findings demonstrate that there are locations where wind facilities could be sited that may limit exposure of migratory birds to these developments. In 27.5% of the area classified as having high or very high potential for wind development, there was only low or moderate potential exposure of migratory concentration areas. Similarly, other studies have demonstrated that U.S. wind energy needs could be met by siting wind development in previously disturbed areas [93] and that mitigation requirements and associated costs could be greatly reduced by avoiding wind development in the most sensitive wildlife habitats [94] . Wyoming could exceed the U.S. Department of Energy’s wind energy goal for the state by 2662% even if development avoided sensitive biological areas [95] , not including the migratory concentration areas presented here.

Our models of migration concentration are limited by the availability and quality of bird occurrence data, predictive GIS layers, and information on migration behavior. The models represent where migration concentration is expected to be highest in most years based on fixed factors, but migration varies among years and is influenced by weather and variation in food resources. The Wyoming bird species occurrence databases contained thousands of records, but only a small portion of these corresponded to the migratory season. Further, most were opportunistic observations rather than data obtained through systematic, unbiased sampling, and some areas of Wyoming were underrepresented. The models were evaluated by experts and assessed against occurrence data, and a logical next step toward improving the models would be structured field validation. Although limited by available data, our migratory concentration models provide a useful spatial synthesis of the information that currently exists and fill a critical gap for landscape-scale planning.

We used the best available knowledge concerning factors that affect migration patterns to create the migration concentration models. For most bird groups, our modeling approach appears to have been effective, based on validation results, but the raptor model is a possible exception.

The raptor model performed well in the expert validation but poorly when compared to existing occurrence data. There may be factors influencing fall migration movement patterns that are not currently understood well enough, or the datasets or methods we used to represent important factors may be limited in some way. An alternative explanation is that the occurrence data are better suited for models of stopovers than for movement, as most observers record birds when they are perching or foraging. For all of the models, we selected model factors, modifiers, and weights based on literature review and expert knowledge. The sensitivity analysis showed that some of these model terms had a greater influence on the outcomes than others. The models were generally most sensitive to factors that affected a relatively large geographic extent (e.g., buffer in the wetland bird model or updrafts and thermals in the raptor model), or because they had been identified as the factor of greatest importance and been valued accordingly. Obviously we would expect the models to be influenced by key factors in this way, yet the sensitivity analysis remains informative because it provides an estimate of the degree to which model results may change given changes in knowledge or assumptions and it provides a range of uncertainty that can be compared with our estimates of bird migration concentration patterns. For the wetland and riparian bird models that had the most model terms, there was very little variation in model results when some modifiers were dropped from the model (e.g., cottonwood or willow abundance for the riparian bird model). This suggests that this modeling approach is robust to minor modifications and that it may be most important to focus on the key factors believed to drive migratory patterns. The sparse grassland bird model was the most sensitive to removal of model terms likely because of the small number of factors, and because we know the least about this group’s migration patterns and behavior.

Wind development has the potential to impact bird populations far beyond the localities of wind facilities if development occurs without regard for migrating birds that may breed or overwinter in other parts of the world. Although migratory birds are protected under international treaties, limited datasets are currently available representing migration at a scale useful to guide development or target protection. Our migratory concentration models provide preliminary spatial data to companies, land management agencies, and others planning for wind development at a useful landscape scale across the state of Wyoming. The migratory concentration models can also help to target conservation efforts for migratory birds, such as conservation easements and stopover habitat enhancements, and our methods could be replicated in other locations or for other groups or species of birds.

Acknowledgments

We thank Marissa Ochsenfeld, Kevin Contos, and Kristina Hooper for literature review, Kristi Gebhart for weather data, and Joe Fargione, Dan Petit, and Valerie Steen for comments improving an earlier manuscript draft. We are grateful to expert reviewers, including Marissa Ahlering, Jason Beason, Bryan Bedrosian, Frank Blomquist, Tim Byer, Anna Chalfoun, Doug Faulkner, Seth Gallagher, CJ Grimes, Allison Holloran, Stephanie Jones, Lorraine Keith, Jim Lawrence, Eric Lonsdorf, Brian Martin, Dave McDonald, Dave Mehlman, Chris Michelson, Bob Oakleaf, Andrea Orabona, Sophie Osborne, Bill Ostheimer, Chris Pague, Rick Pallister, Susan Patla, Chuck Preston, Matt Reddy, Larry Roberts, Jeff Smith, Patricia Sweanor, Steve Tessman, Nick VanLanen, Joni Ward, Nate West, Roger Wilson, and Sue Wolff.

Author Contributions

Conceived and designed the experiments: AP DK HG WE. Performed the experiments: AP MA WE. Analyzed the data: AP MA. Contributed reagents/materials/analysis tools: AP WE MA HC DK HG. Wrote the paper: AP MA WE.

• View Article
• Google Scholar
• 3. Tankersley R, Orvis K (2003) Modeling the geography of migratory pathways and stopover habitats for neotropical migratory birds. Ecol Soc 7.
• 5. Energy Information Administration (2011) Annual Energy Outlook 2011: with projections to 2035. Washington, DC: U.S. Department of Energy.
• 6. Energy Information Administration (2011) Annual Energy Review 2010. Washington, DC: U.S. Department of Energy.
• 7. The White House (2011) Blueprint for a secure energy future. Washington, DC: The White House.
• 9. Arnett EB, Inkley DB, Johnson DH, Larkin RP, Manes S, et al.. (2007) Impacts of wind energy facilities on wildlife and wildlife habitat. Wildlife Society Technical Review. Bethesda, Maryland. 49.
• 12. Erickson WP, Johnson GD, Strickland MD, Young DP, Sernka KJ, et al.. (2001) Avian collisions with wind turbines: a summary of existing studies and comparisons to other sources of avian collision mortality in the United States. Washington, DC: National Wind Coordinating Committee.
• 13. U.S. Fish and Wildlife Service (2012) U.S. Fish and Wildlife Service land-based wind energy guidelines.
• 18. Munson MA, Webb K, Sheldon D, Fink D, Hochachka WM, et al.. (2011) The eBird Reference Dataset, Version 3. Ithaca, New York: Cornell Lab of Ornithology and National Audubon Society.
• 19. Smith JP (2009) Fall 2009 raptor migration studies at Commissary Ridge in southwestern Wyoming. Salt Lake City, UT: Hawkwatch International, Inc.
• 20. Smith JP, Neal M (2001) Fall 2000 exploratory raptor migration counts in Wyoming and southwestern Montana. Salt Lake City, UT: Hawkwatch International, Inc.
• 24. Franklin J (2009) Mapping species distributions: spatial inference and prediction. Cambridge, MA: Cambridge University Press.
• 26. Department of Energy (2008) 20% wind energy by 2030: Increasing wind energy’s contribution to U.S. electricity supply. Oak Ridge, TN: Office of Scientific and Technical Information.
• 27. Copeland H, Pocewicz A, Kiesecker J (2011) The geography of energy in Western North America: potential impacts to terrestrial ecosystems. In: Naugle DE, editor. Energy Development and Wildlife Conservation in Western North America. Washington, DC: Island Press.
• 28. American Wind Energy Association (2012) Wind energy facts: Wyoming. Washington, DC.
• 29. Newton I (2008) The migration ecology of birds. Amsterdam: Academic Press.
• 30. Kingsley A, Whittam B (2003) Wind turbines and birds, a guidance document for environmental assessment. Phase 3 draft report prepared by Bird Studies Canada for Canadian Wildlife Service. Gatineau, Quebec. p. 79.
• 32. Bellrose FC (1980) Ducks, geese, and swans of North America. Harrisburg, PA: Stackpole Books.
• 36. Hothem RL, Brussee BE, Davis WE Jr (2010) Black-crowned Night Heron ( Nycticorax nycticorax ). In: Poole A, editor. The Birds of North America Online. Ithaca, NY: Cornell Lab of Ornithology.
• 37. Gammonley JH (1996) Cinnamon teal ( Anas cyanoptera ). In: Poole A, editor. The Birds of North America Online. Ithaca, NY: Cornell Lab of Ornithology.
• 41. Knopf FL, Evans RM (2004) American white pelican ( Pelecanus erythrorhynchos ). In: Poole A, editor. The Birds of North America Online. Ithaca, NY: Cornell Lab of Ornithology.
• 44. Mowbray T (2002) Canvasback ( Aythya valisineria ). In: Poole A, editor. The Birds of North America Online. Ithaca, NY: Cornell Lab of Ornithology.
• 45. Mitchell CD, Eichholz MW (2010) Trumpeter Swan ( Cygnus buccinator ). In: Poole A, editor. The Birds of North America Online. Ithaca, NY: Cornell Lab of Ornithology.
• 47. Reed JM, Oring LW, Gray EM (2013) Spotted Sandpiper ( Actitis macularius ). In: Poole A, editor. The Birds of North America Online. Ithaca, NY: Cornell Lab of Ornithology.
• 48. Ryder RA, Manry DE (1994) White-faced Ibis ( Plegadis chihi ). In: Poole A, editor. The Birds of North America Online. Ithaca, NY: Cornell Lab of Ornithology.
• 49. Rubega MA, Schamel D, Tracy DM (2000) Red-necked Phalarope ( Phalaropus lobatus ). The Birds of North America Online. Ithaca, NY: Cornell Lab or Ornithology.
• 50. Alexander SA, Gratto-Trevor C (1997) Shorebird migration and staging at a large prairie lake and wetland complex: the Quill Lakes, Saskatchewan. Ottawa, Canada.
• 56. Mowbray TB, Ely CR, Sedinger JS, Trost RE (2002) Canada Goose ( Branta canadensis ). In: Poole A, editor. The Birds of North America Online. Ithaca, NY: Cornell Lab of Ornithology.
• 58. Skagen SK, Hazelwood R, Scott ML (2005) The importance and future condition of western riparian ecosystems as migratory bird habitat: USDA Forest Service General Technical Report.
• 60. Wethington SM, Russell SM, West GC (2005) Timing of hummingbird migration in southeastern Arizona: implications for conservation. In: Ralph CJ, Rich TD, editors. Bird conservation implementation and integration in the Americas: USDA Forest Service General Technical Report. 646–651.
• 61. van Riper CI, Paxton KL, van Riper CJ, van Riper LJ, McGrath LJ, et al.. (2008) The role of protected areas as bird stop-over habitat: ecology and habitat utilization by migrating land birds within Colorado River riparian forests of southwestern North America. In: Harmon D, editor. Protected Areas in Park Management. Hancock, MI: George Wright Society. 312–320.
• 62. Goodrich LJ, Smith JP (2008) Raptor migration in North America. In: Bildstein JP, Smith E, Ruelas Inzunza E, Veit RR, editors. State of North America’s Birds of Prey. Cambridge, MA and Washington, DC: Nuttall Ornithological Club and American Ornithologist’s Union.
• 63. Heintzelman DS (1986) The migration of hawks. Bloomington, IN: Indiana University Press.
• 64. Kerlinger P (1989) Flight strategies of migrating hawks. Chicago, IL: University of Chicago Press.
• 65. Steenhof K (1998) Prairie Falcon ( Falco mexicanus ). In: Poole A, editor. The Birds of North America Online. Ithaca, NY: Cornall Lab of Ornithology.
• 66. Steenhof K, Fuller MR, Kochert MN, Bates KK (2005) Long-range movements and breeding dispersal of Prairie Falcons from southwestern Idaho. The Condor 481–496.
• 67. White CM, Clum NJ, Cade TJ, Hunt WG (2002) Peregrine Falcon ( Falco peregrinus ). The Birds of North America Online. Ithaca, NY: Cornell Lab of Ornithology.
• 68. Bechard MJ, Schmutz JK (1995) Ferruginous hawk ( Buteo regalis ). In: Poole A, editor. The Birds of North America Online. Ithaca, NY: Cornell Lab of Ornithology.
• 69. Bechard MJ, Houston CS, Sarasola JH, England AS (2010) Swainson’s Hawk ( Buteo swainsoni ). In: Poole A, editor. The Birds of North America Online. Ithaca, NY: Cornell Lab of Ornithology.
• 70. Beason RC (1995) Horned Lark ( Eremophila alpestris ). In: Poole A, editor. The Birds of North America Online. IthacaNY: Cornell Lab of Ornithology.
• 71. Vickery PD (1996) Grasshopper sparrow ( Ammondramus savannarum ). In: Poole A, editor. The Birds of North America Online. Ithaca, NY: Cornell Lab of Ornithology.
• 72. Hill DP, Gould LK (1997) Chestnut-collared longspur ( Calcarius ornatus ). In: Poole A, editor. The Birds of North America Online. Ithaca, NY: Cornell Lab of Ornithology.
• 73. Knopf FL, Wunder MB (2006) Mountain plover ( Charadrius montanus ). The Birds of North America Online. Ithaca, NY: Cornell Lab of Ornithology.
• 74. Poulin R, Todd DL, Haug EA, Millsap BA, Martell MS (2011) Burrowing owl ( Athene cunicularia ). In: Poole A, editor. The Birds of North America Online. Ithaca, NY: Cornell Lab of Ornithology.
• 79. Faulkner DW (2010) Birds of Wyoming. Greenwood Village, CO: Roberts and Company Publishers.
• 81. R Development Core Team (2013) R: A Language and Environment for Statistical Computing. Vienna, Austria: R Foundation for Statistical Computing.
• 82. Hijmans RJ, van Etten J (2013) raster: Geographic data analysis and modeling. R website. http://CRAN.R-project.org/package=raster . Accessed March 1, 2013.
• 87. O’Donnell MS, Fancher TS (2010) Spatial mapping and attribution of Wyoming wind turbines: U.S. Geological Survey.
• 88. National Renewable Energy Laboratory (2008) Annual average wind resource potential of the northwestern United States at a 50 meter height: National Renewable Energy Laboratory.
• 89. Majka D, Jenness J, Beier P (2007) CorridorDesigner: ArcGIS tools for designing and evaluating corridors.Corridor Designer website. http://corridordesign.org . Accessed December 1, 2011.
• 97. U.S. Environmental Protection Agency (2010) Level III ecoregions of the continental United States (revision of Omernik, 1987). Corvallis, OR: US EPA National Health and Environmental Effects Research Laboratory.
• 98. Keinath DA, Andersen MD, Beauvais GP (2010) Range and modeled distribution of Wyoming’s species of greatest conservation need. Laramie, WY: Wyoming Natural Diversity Database.
• 99. Davidson A, Aycrigg J, Grossmann E, Kagan J, Lennartz S, et al.. (2009) Digital Land Cover Map for the Northwestern United States. Moscow, Idaho: Northwest Gap Analysis Project, USGS GAP Analysis Program.
• 100. Jenness J (2006) Topographic position index (TPI) v.1.2. Flagstaff, AZ: Jenness Enterprises.
• 101. Skamarock WC, Klemp JB, Dudhia J, Gill DO, Barker DM, et al.. (2008) A description of the advanced research WRF version 3. Boulder, CO.
• 102. Comer P, Faber-Langendoen D, Evans R, Gawler S, Josse C, et al.. (2003) Ecological systems of the United States: A working classification of U.S. terrestrial systems. ArlingtonVA: NatureServe. 75 p.

Essay on “Bird Migration” for School, College Students, Essay, Paragraph and Speech for Class 10, Class 12, College and Competitive Exams.

Bird Migration

In countries like England, France and North America, when the weather gets very cold in winter, rich people move to warm climates. We have seen rich people move to hill resorts and live there when the weather gets hot in summer.

The birds and animals also move from one place to another when the climate changes. It is one of the mysteries of nature that birds are able to travel thousands of kilometers and come back to their original resting places at regular intervals.

During September and November flocks of birds come from somewhere and then go away.

Bird watchers after years of patient observation and study of these migrating birds have concluded that there is a regular and systematic about their behaviour. People used to think that small birds such as Swallows, Nightingales and Cuckoos went to sleep during the winter; but now it is known that they go to warm countries.

Why do birds migrate? They are not directly affected by the cold because of their feather covering and warm blood, but in winter getting food is not easy.

Snow lies thick on the ground in winter and even lakes and rivers are frozen over. The weather is such that birds will not be able to catch either insects or fish. If they do not migrate, they will perish. As the nights are short the time available for searching for food is short, So, they have to fly over to warm places.

The birds fly to the same places and return to their original breeding grounds with amazing accuracy. During migration, it is usually the young birds that fly at the front and the older ones in the rear. Though the young ones have never flown that way, yet they fly to the right places and return to the right places covering hundreds of kilometers. They do not need any training in finding their direction during migration, for they are guided by instinct. Birds from north and north western parts of India fly to South India and Sri Lanka.

It is now found that some of the white strokes that are seen in India come from Germany.

Birds such as ducks and geese fly at a speed of between sixty-five and ninety kilometers per hour. Some birds fly from six to eleven hours a day. Some birds can fly 885 kilometers non-stop in about eleven hours. A bird known as the Eastern Golden plover which comes to India from western Alaska and North eastern Siberia flies 3200 kilometers non-stop. The snipe flies 4800 kilometers over the sea from Japan to Australia. There is scientific evidence to prove all this. They fly at a height of 1000 meters and 4000 meters above the ground.

More and more people are taking an interest in bird behaviour and in course of time, the answers to a lot of questions about bird migration will be available.

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June 11, 2024

This article has been reviewed according to Science X's editorial process and policies . Editors have highlighted the following attributes while ensuring the content's credibility:

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Specialist and migratory birds in North America at greater risk under climate change

by University of Illinois College of Agricultural, Consumer and Environmental Sciences (ACES)

Following decades of decline, even fewer birds will darken North American skies by the end of the century, according to a new analysis by scientists at the University of Illinois Urbana-Champaign. Their study is the first to examine the long-term effects of climate change on the abundance and diversity of bird groups across the continent as a whole while accounting for additional factors that put birds at risk, such as pesticides, pollution, land use change, and habitat loss.

"Many studies try to attribute causes like climate or land use change to bird population decline based on field-level observation. However, there has been no large-scale statistical analysis that puts together historical data on biodiversity and climate for North America," said study co-author Luoye Chen, an assistant professor at the Hong Kong University of Science and Technology (Guangzhou). Chen completed the research during his doctoral program in the Department of Agricultural and Consumer Economics (ACE), part of the College of Agricultural, Consumer and Environmental Sciences (ACES) at Illinois.

The study relies on data from the North American Breeding Bird Survey, which gathers detailed field observations of more than 400 bird species across the continent each spring. Analyzing bird population trends between 1980 and 2015 together with climate data from the same timeframe, the researchers show a modest but significant dip in the number and diversity of birds overall and a larger drop for specialist and migratory groups. The analysis also projects scenarios for the years 2095 to 2099, with still greater declines.

"Even after controlling for a lot of other things, we see that climate change has a significant negative impact on birds," said study co-author Madhu Khanna, professor in the Department of ACE and director of the Institute for Sustainability, Energy, and Environment at Illinois. "This is just one more reason we need to make serious efforts to mitigate climate change as soon as possible."

Chen says common birds like sparrows that occupy a wide variety of habitats throughout North America are less affected by climate change. According to the analysis, these generalist species declined about 2.5% during the 1980–2015 period, with projected declines between 1 and 3% by century's end.

Specialist species like the threatened spotted owl and the endangered red-cockaded woodpecker have more specific habitat and diet requirements, putting them at greater risk in a changing environment. Chen says climate was responsible for about 5% of their decline between 1980 and 2015, with losses up to 16% projected by 2099.

The subset of specialist species that are also migratory, like the whooping crane, mirror trends for specialists as a whole. The researchers say although migrants might have the ability to move to more favorable locales, birds don't have the advantage of weather apps to check conditions in their destination before taking off.

"These birds have generations-long patterns of migration. They're going to migrate no matter what, and they don't know what's waiting at the other end. It may be too hot or dry for them," Khanna said. "But climate doesn't just affect birds' health directly in terms of temperature. It could cause changes in their food supply along their migration route."

The researchers also tested the hypothesis that birds could adapt to a warming climate by separately analyzing smaller chunks of time. If birds declined at a greater rate early in the warming period and slowed down later, that would indicate adaptation to higher temperatures over time.

"Previous small-scale field studies showed potential adaptive behaviors in birds responding to climate change," Chen said. "Unfortunately, we didn't find evidence to support adaptation over time. In the long term, we still found significant reductions."

Although losses in the 2 to 16% range may not sound as alarming as some predictions, the researchers emphasize that their analysis represents the average loss across an entire continent. Some bird species and groups may be much more significantly affected, especially in specific regions. Also, any further reduction in bird abundance or diversity may be too much, as they play important roles in the ecosystem, from pollination to insect control and beyond.

"Many of the specialist birds really are quite special. Some are endangered species, and others are endemic to very small areas," Chen said. "We can't afford to lose any of them, given their crucial roles in ecosystems."

The study, " Heterogeneous and long-term effects of a changing climate on bird biodiversity ," is published in Global Environmental Change Advances .

Provided by University of Illinois College of Agricultural, Consumer and Environmental Sciences (ACES)

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The Bird Population is Dwindling in “The Land of Enchantment”

Michele Fair

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New Mexico, affectionately known as “The Land of Enchantment,” boasts a diverse landscape of steppes, desert mesas, and high-elevation alpine forests. But in recent years, it appears the state’s once impressive population of bird species is dwindling. In 2020, thousands of migratory birds were found dead throughout the state, and researchers at Los Alamos National Laboratory believe it’s largely due to climate change.

While millions of birds fly across North America to migrate each year, many species experienced extreme weather events in 2020, most notably a period of excessively high temperatures in Colorado and New Mexico. Next came a sudden cold front soon followed by massive forest fires in the region that produced copious amounts of smoke. According to Jeanne Fair, a scientist at Los Alamos National Lab, there was a “mass mortality of birds” that happened “literally within a few days.”

These extreme changes weren’t just isolated to 2020 and many scientists believe they’re likely to happen again. As temperatures fluctuate outside of the norm during the migration season, it kills valuable food sources for birds like specific plants and insects. Without plentiful food readily available, many birds don’t have adequate fuel to help them on the long trek as they fly from one region to the next. In New Mexico’s case, the birds happened to die there, with the bulk of the animals found scattered across White Sands Missile Range.

Extreme Heat Poses a Serious Threat

In July 2023, parts of New Mexico saw triple-digit temperatures. According to UNM Professor of Biology, Blair Wolf, “Chronic heat really stresses birds and other wildlife.” Birds lose water through panting and must replenish the water they lose. Without proper access to shade and water, “This leads to increasing stress and water loss,” said Wolf. He also noted that he saw nestlings and dead adult birds at his home in Mimbres, New Mexico, including Purple Martins and Black Phoebes.

According to the Audubon Society, the increasing frequency of wildfires and dry conditions have led to the loss of pine trees that provide shade, food, and shelter for many bird species. A reduction in vegetation cover also affects nesting birds, while low levels in the Rio Grande have strained crucial ecosystems. The desertification of rangelands also has negative impacts on birds. The organization says New Mexico will likely experience more intense and frequent wildfires and decreased water flows in rivers in the coming decades.

Without swift, corrective action, the beautiful birds who depend on resources in The Land of Enchantment could lose over half of their current range as they search for more suitable habitats and climate conditions in other regions.

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Guest Essay

Why the New Human Case of Bird Flu Is So Alarming

By Rick Bright

Dr. Bright is a virologist and the former head of the Biomedical Advanced Research and Development Authority.

The third human case of H5N1, reported on Thursday in a farmworker in Michigan who was experiencing respiratory symptoms, tells us that the current bird flu situation is at a dangerous inflection point.

The virus is adapting in predictable ways that increase its risk to humans, reflecting our failure to contain it early on. The solutions to this brewing crisis — such as comprehensive testing — have been there all along, and they’re becoming only more important. If we keep ignoring the warning signs we have only ourselves to blame.

H5N1 has long been more than a bird problem. The virus has found its way into dairy cattle across nine states , affecting 69 herds that we know about. Of the three human cases of H5N1 that have been identified, all involve farmworkers who were in direct contact with infected cows or milk. The first two cases were relatively mild, involving symptoms like eye irritation, or conjunctivitis. However, the most recent case has shown more concerning signs, including coughing.

The emergence of respiratory symptoms is disconcerting because it indicates a potential shift in how the virus affects humans. Coughing can spread viruses more easily than eye irritation can.

New symptoms should be expected as the virus continues to spread and adapt to humans. Yet our response to this looming danger has been woefully inadequate, particularly in the area of testing.

Testing is our first line of defense in identifying and controlling infectious diseases. It allows health responders to understand the extent of an outbreak, identify who is infected and take measures to prevent further spread.

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