All About Birds Blog

Home Page

Wheatear-peck
By Wesley Hochachka

Which species of North American songbird is widespread enough that it’s found on both eastern and western sides of the continent but is still a rare treat for most birdwatchers? And proportional to its body size, which songbird regularly migrates farther than the globe-trotting Arctic Tern? The answer is: Northern Wheatear, the only North American representative of a widespread Old World genus in the thrush family.

Northern Wheatears breed all the way across northern Eurasia and reach North America in both the west (Alaska and the Yukon) and the east (the Canadian Arctic). So why don’t we get to see them in the winter, the way we get to see Snow Buntings, American Tree Sparrows, and Snowy Owls? Because all of the world’s Northern Wheatears, save a few vagrants, spend the winter in the same region: sub-Saharan Africa.

Not only that, but they take radically different routes to get to Africa, according to recent research presented by Franz Bairlein, director of Germany’s Institute of Avian Research. Bairlein unfolded the Northern Wheatear’s story for a global audience of ornithologists at the International Ornithological Congress in Tokyo, in August. His team used tiny, lightweight geolocator tags to follow wheatears traveling from either side of the North American arctic to their wintering grounds, providing the first hard proof of the long-suspected migration routes of these birds.

WheaterMapwithBags600

Wheatears that breed in far northeastern Canada fly across the Atlantic and then south to Africa. Wheatears from Alaska go around the opposite side of the world, traveling through Siberia and Asia to reach Africa. Despite being the same species, the two groups of birds prepare for and then fly their migration routes in radically different ways. Map adapted from Bairlein et al. 2012; base map courtesy of Google Maps.

The routes could scarcely have been more different. From the eastern arctic of Canada, Wheatears traveled through Greenland to northwestern Europe before flying south to western Africa. Their western arctic compatriots went the other way around the globe: they flew westward to Siberia and then diagonally across Asia to wind up in eastern Africa. The migration distances are astonishing, particularly the Alaskan birds’ journeys, which added up to roughly 15,000 km. Wheatears from the eastern Canadian arctic traveled a mere 7,500 km, although the first leg of their journey was a 3,500 km trans-Atlantic crossing to Europe with only one possible resting point, Greenland, en route.

The time that wheatears spend on these migrations was what I found most surprising: birds traveling across Asia took roughly 3 months to reach Africa and two and a half months to return to North America. That’s comparable to the roughly 3 months that North America’s wheatears spend on their nesting grounds, and is only marginally less than they spend on their wintering grounds (4 or 5 months for western and eastern American arctic, respectively). These birds were spending so little time in any one location that, if they were humans, they possibly would not be considered legal residents of any nation on earth!

The discovery of these travel itineraries has allowed Bairlein’s research group to explore other aspects of migration. Because the two populations of wheatears cross such different types of terrain, the researchers were able to learn about how songbirds in general adapt to the environments that they cross during long-distance travel. Bairlein’s group specifically contrasted the long transoceanic flights of wheatears going east to Europe against the largely overland routes of western arctic birds. And these two populations do prepare for migration differently. Eastern North America’s wheatears fatten massively, approaching double their normal body weight prior to their ocean crossings, whereas western wheatears accumulate far less fat for their journeys. Again, if these birds were human, the rate and extent of fattening, and the physiological processes underlying them, literally would result in these birds being classified as dangerously obese and with type 2 diabetes!

Bairlein’s group also found that these physiological differences are genetically hard-wired into the birds, as are the directions that they navigate. If you were to take the egg from an Alaskan wheatear and transplant it to Baffin Island in the eastern Canadian arctic, the resultant offspring would travel in the wrong direction, westward across North America. Even if such a transplanted bird did head eastward across the Atlantic, its body would still be preparing for a “western” migration and wouldn’t store up enough fuel reserves to reach Europe.

What impressed me the most about Bairlein’s presentation is the way that he applied his knowledge of natural history to select a great study species even though it is not one of the “classic” species of birds for an ornithologist to study. Examples of classic species include Tree Swallows and bluebirds (North America) and Great Tits and Blue Tits (Europe). These birds are easily studied because they live close to researchers and nest in boxes—and scientists have learned a great deal from them. But by starting with this unusual yet inspired choice of study species, Bairlein’s research has shed new light on the ways that migratory birds, and in particular long-distance migrants like Red Knots, Hudsonian Godwits, and Blackpoll Warblers, are adapted to make their great migratory journeys.

More about migration:

(Wesley Hochachka is the assistant director of Bird Population Studies at the Cornell Lab of Ornithology. Top image: Adult male Northern Wheatear in breeding plumage, Alaska, by Mark Peck. Images on map: Northern Wheatear in in Canada by wayne.geater, and in Alaska by Billy Lindblom. All images shared via Birdshare.)

Posted in science | Tagged , , , , | Leave a comment

NearHUmans-HDP550

By Hugh Powell. Originally published in Summer 2014 Living Bird magazine.

The Laysan Albatross has the lukewarm distinction of being perhaps the least-threatened member of the most-threatened group of birds in the world. Of the world’s 22 albatross species, 15 are vulnerable or endangered, according to the IUCN—but the Laysan is at its highest numbers in a century.

That seems like good news, because if ever a group of animals had the deck stacked against it, it’s the albatrosses. At sea they get caught on industrial fishing hooks and eat plastic by the gulletful. At their nests, introduced predators crack their eggs, eat their chicks, and kill adults. They crisscross international boundaries and economic zones. The ships that mistakenly catch them operate in empty seas where no one is watching. They reproduce slowly and can take decades to build back their numbers after a loss.

Even the Laysan Albatross’s prospects are dimming, it appears, as climate change continues to melt ice and raise sea level. All but a couple thousand of the world’s 600,000 breeding pairs nest on low coral atolls, chiefly Laysan and Midway, in the northwestern Hawaiian Islands. These are likely to start going underwater during this century, according to a recent analysis.

KimSMALL

Kim Uyehara, a biologist at Kilauea Point National Wildlife Refuge, prepares to catch a Laysan Albatross for banding. Photo by Hugh Powell.

And yet the story of Laysan Albatrosses is also a story of tenacity and triumph. In the last century they have come back from one severe population decline and are rounding the corner on another. Twice they’ve found aid on the coattails of the Endangered Species Act, despite never having been listed themselves. Will we be able to offer them a way through this next setback?

Any solution for these ocean wanderers is going to be complicated, as I discovered on a visit to the island of Kauai, Hawaii. As their remote atoll homes become unsuitable, these long-lived birds will have to find new colony sites and learn how to live near humans. Simultaneously, humans must learn how to keep albatrosses safe on land and at sea.

On Kauai I went albatross banding with Kim Uyehara, a biologist at Kilauea Point National Wildlife Refuge. In no time she had shoved an albatross under my arm, where it sagged like a bag of groceries you know you are destined to drop. I hung on for dear life as it tried to yank its five-inch bill out of my grasp. Its heart thumped against my rib cage, and it gave a deep sigh of resignation as Uyehara put a black band, A081, on its leg. Moments after I released it, the bird unfolded its seven-foot wings and reclaimed its dignity in the air. One enormous white breast feather lay on the ground where it had stood.

These are the complicated fortunes of the Laysan Albatross—a recurring story of people attempting to solve problems that people made. That we keep succeeding, despite the grim predictions, is one of the best arguments for doing conservation I’ve seen yet.

Midway4SMALL

Using Google Maps’ Street View, you can tour Midway Atoll Wildlife Refuge and see thousands of albatross chicks scattered around the WWII-era buildings and airfields. Explore for yourself.

A Rising Tide

The biggest Laysan Albatross colony in the world is at Midway Atoll. I’ve never been there, but Google Maps has—and their Street View feature gives an idea of what a few hundred thousand albatross chicks look like. Big, gawky birds wearing little halos of gray down are everywhere: among the shrubs; lined up in the shade of old military buildings; under the bike racks; scattered across the flat, flat sand.

(more…)

Posted in conservation | Tagged , , , , , , , , , , , , , , , , | Leave a comment

To this day the Passenger Pigeon story represents the most famous human-caused extinction in history. In this fascinating seminar, Cornell Lab director John Fitzpatrick reviews the remarkable biology and tragic disappearance of this species. Using vivid historical accounts from eyewitnesses (by turns funny and sobering), Fitzpatrick explores how and why a bird could achieve such spectacular numbers and reveals the multiple forces that led to its catastrophic collapse.

Martha, the very last Passenger Pigeon, died in the Cincinnati Zoo in September 1914. A century later, Fitzpatrick contemplates, What have we learned since Martha’s passing? Watch the seminar, titled “Reflections on the Tragic Centenary of the Last Passenger Pigeon”:

The talk took place on September 15, 2014. It was part of the Cornell Lab’s long-running Monday Night Seminar series, a tradition established decades ago by Lab founder Dr. Arthur Allen. If you enjoyed this seminar, check this page for our list of future speakers—we’ll note which upcoming talks will be livestreamed—or come visit us in person! If you missed any talks, please see our index of archived livestreamed seminars.

Posted in conservation, Uncategorized | Tagged , , , , , , | Leave a comment

RHummingbird-Manowitz

By Hugh Powell

Migratory songbirds enjoy the best of both worlds—food-rich summers and balmy winters—but they pay for it with a tough commute. Their twice-a-year migrations span thousands of miles and are the most dangerous, physically demanding parts of their year.

Surprisingly, for many North American species the best route between summer and winter homes is not a straight line, according to new research published in the Proceedings of the Royal Society B. In spring, the study shows, birds follow areas of new plant growth—a so-called “green wave” of new leaves and numerous insects. In fall, particularly in the western U.S., they stick to higher elevations and head directly southward, making fewer detours along the way for food.

“We’re discovering that many more birds than anyone ever suspected fly these looped migrations, where their spring and fall routes are not the same,” said Frank La Sorte, a research associate at the Cornell Lab of Ornithology. “And now we’re finding out why—they have different seasonal priorities and they’re trying to make the best of different ecological conditions.”

The research—the first to reveal this as a general pattern common to many species—may help land managers improve conservation efforts by improving their understanding of how birds use habitat seasonally.

LazuliRufous

The Rufous Hummingbird and Lazuli Bunting are two of the 26 western species in the study. Rufous Hummingbird by Brian Hampson; Lazuli Bunting by Todd Steckel, both via Birdshare.

“All this information helps us understand where we should focus conservation across time,” La Sorte said. “Then we can drill down and make local and regional recommendations. In the West particularly, the systems are very complicated, but we’re starting to build a nice foundation of knowledge.”

In a 2013 study, La Sorte and his colleagues discovered that many species of North American birds flew looping, clockwise migration routes. But they could only partially explain why. For eastern species, it was clear from atmospheric data that the birds were capitalizing on strong southerly tailwinds in spring over the Gulf of Mexico and less severe headwinds in fall. By adding the effect of plant growth, the new study helps explain why western species also fly looped routes.

The study examined 26 species of western birds, including the Rufous Hummingbird and Lazuli Bunting, and 31 species of eastern birds such as the Wood Thrush and Black-throated Blue Warbler. Birds on both sides of the continent showed a strong tendency to follow the flush of green vegetation in spring.

WThrushBTBlue

The Wood Thrush and Black-throated Blue Warbler are two of the 31 eastern species in the study. Wood Thrush by Kelly Colgan Azar; Black-throated Blue Warbler by Mitch Vanbeekum, both via Birdshare.

In the relatively continuous forests of the eastern U.S. this tight association with green vegetation persisted all summer and into fall. In the West, however, green space occurs along rivers and mountains, and is often isolated by expanses of desert or rangeland.

“Western migrants can’t necessarily cross big stretches of desert to get to the greenest habitat when it’s the most green,” La Sorte said. “So in spring, they stick to the foothills where insects are already out. But in fall they tend to migrate along browner, higher-elevation routes that take them more directly south.”

For decades scientists have known that some herbivorous species, including geese and deer, follow the “green wave” of spring vegetation on their northward migrations. La Sorte’s study is the first to extend that idea to insectivorous species, which are tiny (most weigh an ounce or less) and much harder to study using tracking devices.

The researchers solved that problem by using sightings data—lots of it—to substitute for tracking data. They analyzed 1.7 million crowdsourced bird checklists from eBird, a free online birding-list program, to construct a detailed picture of species occurrence for each week of the year. Then they used satellite imagery to determine the ecological productivity—or amount of new plant growth—across the U.S.

What emerged was a composite picture of where each species occurred, week by week, that the scientists then compared with satellite-derived estimates of where the greenest or most productive habitats were.

“Up till eBird data became available, people have had to look at migration on a species by species basis, by tracking individual birds,” La Sorte said. “We’re bringing in the population perspective using big data, and that’s enabling us to describe general mechanisms across species.”

In addition to La Sorte, the paper’s authors include Daniel Fink, Wesley Hochachka, and Steve Kelling of the Cornell Lab, and John DeLong of the University of Nebraska, Lincoln. The research was supported in part by grants from Leon Levy Foundation, Wolf Creek Foundation, and the National Science Foundation.

Related research on looped migration strategies:

(Top image: Rufous Hummingbird by Lois Manowitz via Birdshare)

Posted in conservation, science | Tagged , , , , , , , , | 1 Comment
Older Entries |