Last August a female whimbrel took off from the treeless tundra of Southampton Island, which guards the iceberg-choked entrance to Hudson Bay in the Canadian subarctic, and set a course southeast.
Long-limbed and gray-brown, she was the size of a small duck, bearing the field marks that make this shorebird instantly identifiable鈥攄ark stripes on the crown of her head, and a long, thin, drooping crescent of a bill. It gives the whimbrel its genus name: Numenius, Greek for 鈥渘ew moon.鈥
Southampton had merely been a way station for her; some weeks earlier she had arrived there from her breeding grounds on the Mackenzie River delta in the Northwest Territories, some 1,500 miles and 52 hours of flying time to the northwest. Now her bill was stained purple from weeks of gorging on the autumn tundra鈥檚 bounty鈥攂lueberries, crowberries, and cloudberries, all of which her body had converted to thick layers of fat, fuel for the incredible journey ahead.
Tapered wings pumping without pause or rest, she flew east across Hudson Bay, passing thereafter over the rugged Ungava Peninsula of northern Quebec, then above the trackless boreal forests and wild rivers of Labrador. After 1,500 miles of unbroken flight, averaging 43 miles per hour, she left land behind, flying out into the open ocean somewhere south of Newfoundland, and by the early 2000s we started to see significant declines in whimbrels,鈥 Watts says. 鈥淲e didn鈥檛 feel it was a local issue, because the birds are feeding on fiddler crabs and marine worms, which are super-abundant. We didn鈥檛 know if the problem was on the breeding grounds or the wintering grounds, but where were they breeding? Where were they wintering? We realized we needed to get more of a full, annual-cycle picture.鈥
The first whimbrel Watts鈥檚 team had tagged, a bird nicknamed Winnie that they captured in May 2008, stunned researchers by flying more than 3,200 miles in just six days to the Mackenzie River delta in the Northwest Territories and then, after a brief rest, continuing on to the North Slope of Alaska to breed.
鈥淭hat was just a complete shock,鈥 Watts recalls. Scientists had assumed the eastern and western populations of whimbrels were discrete, with their own migration routes and wintering areas. 鈥淭hat took the roof off of what we thought we knew, and told us for the first time that there was all this crossover and mixing going on.鈥
As Watts鈥檚 team and their partners deployed more transmitters, there were more surprises. 鈥淲e assumed these birds were coming back through the Delmarva every year, but the peninsula鈥檚 a hundred kilometers long. We had no idea that the same bird would come back to the same creek, to exactly the same mudflat, year after year,鈥 Watts says. As the whimbrels roved the world鈥攆rom the high Arctic, where they nest, to the mangrove swamps and mudflats of the Caribbean and northeastern South America, where they spend the winter鈥攖hey were showing an astounding level of what biologists call site fidelity.
Hope is a good example. Following her daily satellite fixes, Center for Conservation Biology scientists like Fletcher Smith saw her scribe looping flight paths across half the Western Hemisphere鈥攁nd came to realize how utterly dependent this bird was on a mere handful of locations where she could rest and feed after epic flights.
鈥淗ope is basically using just four sites in the world, while crossing almost 12,000 miles a year,鈥 Smith says, his voice tinged with equal measures of wonder and worry. It is both a migratory miracle and a conservation nightmare, because a bird that depends on so few stopover places is in deep trouble if any of those spots proves dangerous. This, too, would be a lesson that the whimbrels would teach.
The ability to pinpoint the movements of a single bird across thousands of miles and over many years, thanks to ever-smaller and more advanced tracking devices, is a triumph for wildlife research. But it has also revealed how woefully shortsighted our understanding of birds has been since鈥攚ell, since the beginning of ornithology. The study of birds arose in the Northern Hemisphere, in Europe and North America. For centuries, ornithologists there wore the equivalent of geographic and seasonal blinders when it came to their research, concentrating largely on what happened to migratory birds during the breeding season, when the birds, too, were in the north.
As a result, we knew little about what happened to birds during the seven or eight months鈥攎ost of the year鈥攚hen they were migrating or on their wintering grounds. Many scientists dismissed those nonbreeding periods as basically unimportant.
鈥淵ou can鈥檛 look at this discrete breeding period alone and expect to understand the biology of birds鈥攂ut that鈥檚 what we鈥檝e done as biologists,鈥 says Peter Marra, a research scientist at the Smithsonian Migratory Bird Center within the Smithsonian Conservation Biology Institute in Washington, D.C. 鈥淥ne of the obvious reasons why we鈥檝e done so is because it鈥檚 in our own backyard. The second one is that we haven鈥檛 really been able to follow these birds throughout the year, so there鈥檚 been a disconnect between where these birds breed and where they winter.鈥
But that is changing rapidly, as ornithologists like Marra embrace the notion of 鈥渕igratory connectivity鈥濃攍inking individuals and populations throughout their annual cycle. Only by following migratory animals during the entire year can scientists comprehend what physiological feats wild travelers are accomplishing鈥攁nd begin to tease out the layers of selection pressure that drive their evolution.
And it鈥檚 only through such all-encompassing approaches, Marra and others argue, that conservationists can hope to stem the declines and disappearances of migratory species, from songbirds to salmon and whales. That鈥檚 why Smithsonian鈥檚 Marra and Sue Haig from the U.S. Geological Survey, along with dozens of other scientists, and with support from 爆料公社, have created the Migratory Connectivity Project to encourage research into this poorly understood area.
The notion of connectivity has changed the way Marra looks at almost everything related to migratory birds. Whether as a cause or a consequence, Marra is now one of the leaders in the growing field of migratory connectivity research, which grew out of his decades of studying American redstarts on their wintering grounds in Jamaica. He found, to his surprise, that what happens in the Caribbean doesn鈥檛 stay in the Caribbean.
Redstarts practice something called sexual habitat segregation鈥攃ommon in many birds鈥攚here adult males grab the best winter territories, and on down the dominance ladder to immature females, which get the worst. 鈥淏est鈥 means wettest and buggiest, mangrove swamps being preferred in Jamaica. By testing stable chemical isotopes in redstart blood, muscle, and toenails in the breeding area, Marra and his colleagues have found that the birds that winter in the wetter habitats are able to head north on their spring migration earlier and arrive on the nesting grounds first.
What鈥檚 more, the quality of their winter territory has what Marra calls 鈥渃arryover effects鈥 right into the breeding season. 鈥淲hen you track those birds and follow their reproductive success, you find that birds that are originating in wet habitat have significantly higher reproductive success than birds coming back from dry habitat,鈥 Marra says. 鈥淚t doesn鈥檛 matter what happens on the breeding grounds鈥攎ost of the variation in the number of young fledged is controlled by winter habitat.鈥
These findings, which made the ornithological world sit up and take notice, are of more than academic importance. Winters in Jamaica have been getting steadily drier for the past 16 years, and if鈥攁s climate models predict鈥攖hat trend continues, it could mean that no matter how much management we do here in North America, birds like redstarts could be in trouble.
That makes the timing perfect for the Migratory Connectivity Project. The goal is to harness interest in connectivity with incredible advances in technology and analytical techniques like isotope studies. While satellite transmitters like the ones used on the whimbrels are still relatively bulky, restricting their use to larger species, new inventions are allowing scientists to track smaller birds with undreamed-of precision.
Take light-sensitive geolocators, for instance, which weigh less than a penny and record moment-to-moment changes in sunlight to calculate a rough latitude and longitude for two years or more. In 2007 a team of scientists including Iain Stenhouse affixed geolocators to Arctic terns nesting in Greenland and Iceland. They found that some of the terns were traveling more than 47,000 miles in a single year鈥攏early double the distance ornithologists thought they migrated.
鈥淗ad someone told me just 10 years ago that we would be able to track small seabirds like terns across whole oceans and entire years鈥攏ever mind that I鈥檇 be involved in such a project鈥擨 would have been completely incredulous,鈥 says Stenhouse, who studies seabirds at the Biodiversity Research Institute in Maine.
Nor did they stop with terns. In 2007 he and two colleagues used geolocators to track Sabine鈥檚 gulls from their Arctic breeding grounds to wintering sites off southern Africa鈥攁t almost 25,000 miles, the longest migration known for any gull. 鈥淥ver the last decade or so we have seen an all-out revolution in the study of avian migration,鈥 Stenhouse says. 鈥淪eeing the actual tracks of individual birds traversing the face of a globe still gives me shivers.鈥
Using these new techniques, scientists are redrawing the maps of migration, discovering how regional populations are often taking very different routes to disparate wintering grounds, or discovering new over-winter areas entirely. One of Marra鈥檚 students has used geolocators to discover the previously unknown destination for eastern willets (they travel to southern Brazil, as it turns out), while other researchers have used the devices to track the ever-shifting movements of bobolinks after they leave the grasslands of North America.
鈥淭he bobolink stories are just amazing,鈥 Marra says. 鈥淭hese birds are in an almost constant circuit of movement, from their breeding areas in Vermont or Nebraska down to their wintering area in northern South America, then back up to what might be multiple breeding areas. It鈥檚 just a fascinating story we鈥檙e learning from these light-level geolocators.鈥
Not all the techniques being marshaled to understand migratory connectivity involve high-tech gadgets. Bird bands, which scientists have used for more than a century, may seem unsophisticated, but they also provide a treasure trove of untapped data. Last year Marra and two colleagues combined banding data and information from geolocators to map the connections between different populations of gray catbirds, showing that those from the Midwest take a circum-Gulf route to winter in Central America, while those from the mid-Atlantic region flit down to Florida and the Caribbean each fall.
Building on that, the Migratory Connectivity Project is undertaking the first comprehensive analysis of millions of band-recovery records, with the aim of creating an atlas of migratory connectivity for hundreds of species.
For Hope the whimbrel鈥resting on Cape Cod after surviving her passage through Tropical Storm Gert, her transmitter sending regular reports back to Fletcher Smith and Bryan Watts at the Center for Conservation Biology鈥攖he journey was far from over. After pausing just a day, she flew down the coast to the Eastern Shore, lingered a month on the same mudflats and salt marshes where she was originally tagged, then on September 9 flew out over the sea. Late summer was a bad time to be aloft on the western Atlantic, however. Another whimbrel tagged by Watts and his partners, a female named Goshen, normally puddle-jumps from the Eastern Shore to the northeastern coast of South America near Belem, Brazil. Instead, on August 22, she hit the violent eastern edge of Hurricane Irene, then a Category 3 storm, and three days later made an emergency landing on the island of Antigua.
A third female whimbrel, named Machi, which also normally flies nonstop from Virginia to Suriname and eastern Brazil, rode out Irene on the Eastern Shore, then took off only to get tangled up with Tropical Storm Maria before making a safe landfall on the island of Montserrat. Back in Virginia, Smith and Watts were watching the satellite tracks with worry and breathless wonder鈥攕eeing how the fragile birds cut through some of the most ferocious storms on the planet and survived. Through the Internet, on which the birds鈥 travels could be followed in real time as colorful dots traversing a map of the hemisphere, uncounted others were able to share in the drama, too.
鈥淢ost of these birds are entering the storms on the northeast quadrant, where the winds are in their faces, and then going straight through the eye of the hurricane,鈥 Smith says. 鈥淚t looks like these whimbrels are strong enough to negotiate even these huge storms.鈥
Strong but not invulnerable. Wrung out by their journeys, both Machi and Goshen began island-hopping down the Lesser Antilles instead of flying the rest of the way to South America in a single leap. On September 12, both birds independently approached Guadeloupe, a French-controlled island鈥攚hich, like several islands in the Antilles, maintains a tradition of legal, basically uncontrolled shorebird hunting.
Tired and hungry, the two birds zeroed in on some of the only wetland habitat on the island鈥攕o-called 鈥渟hooting swamps,鈥 where middle- and upper-class Creole hunters watch the weather, and wait for storms to ground exhausted shorebirds. There are 3,000 such hunters on the tiny island, dozens of whom ring the shooting swamps at a time, sitting in lawn chairs with shotguns ready for yellowlegs, dowitchers, semipalmated sandpipers, and other migrants. Other gunners patrol freshly cut sugarcane fields, where upland sandpipers and American golden-plovers feed.
Machi and Goshen both died before they could even land on Guadeloupe. Their deaths enraged conservationists鈥攁nd provided a tragic reminder that even the briefest portion of an annual cycle can have devastating consequences for a migratory bird.
Are the steady declines in whimbrels, semipalmated sandpipers, and several other shorebirds due to the heavy but鈥攗ntil now鈥攍ittle-known hunting pressure these species face on a few Caribbean islands and along the South American coast?
鈥淐learly, what鈥檚 going on down there is a throwback to an earlier time,鈥 Watts says. 鈥淲e hunt woodcock and snipe up here, but it鈥檚 a managed hunt, and we have good data to back it up. This is an open-ended hunt鈥攖here鈥檚 no bag limit. In just one fallout last year, 2,000 to 3,000 golden-plovers were shot; one hunter said he killed a hundred in a single day. This is legal open-ended hunting.鈥
If there鈥檚 a bright side, it鈥檚 that the very public deaths of two well-known migrants is finally spurring an examination of the unregulated shooting on Guadeloupe and elsewhere in the Caribbean. The local newspaper even covered the whimbrels鈥 death, labeling the hunters 鈥渕urderers,鈥 and there are indications that whimbrels and red knots may be added to the list鈥攚idely ignored by gunners鈥攐f protected species. On Barbados (an independent country where the last Eskimo curlew鈥攖he whimbrel鈥檚 closest relative鈥攚as shot in 1963, and which is also a gunning hotspot), one shooting swamp is being bought and converted to a sanctuary.
And what of Hope? She also had to contend with Tropical Storm Maria, her second major gale of the autumn, but she averaged 31 mph through even the worst parts of the storm. On Sept. 14鈥83 hours and 1,624 miles after leaving Virginia, and nearly 6,000 miles from her nesting site in the Northwest Territories鈥攕he made landfall on the island of St. Croix.
There she found a very different world than the gauntlet that awaits migrant shorebirds on islands like Guadeloupe, Martinique, and Barbados. As one of the U.S. Virgin Islands, St. Croix is subject to U.S. laws, including the international treaty that protects shorebirds and to which French possessions like Guadeloupe are not signatories.
Yet even though 爆料公社 and BirdLife International recognize Hope鈥檚 favored wintering site鈥攁 St. Croix mangrove swamp known as Great Pond鈥攁s an Important Bird Area, a huge resort development has been proposed that would essentially envelop the bay. Local environmentalists have stalled that project thus far, but disturbance by four-wheel-drive vehicles and illegal dumping are ongoing problems. There are many dangers for a migratory bird, and only a few come out of the barrel of a gun.
But for the time being, at least鈥攁nd true to her name鈥擧ope was safe from all but the mostly natural dangers to which shorebirds have always been subject. And true to her nature, which depends on a few extraordinarily small, localized places in her hemispheric wanderings, Hope would defend a tiny winter territory on St. Croix. Every time she has been observed at Great Pond, it has been within 10 yards of the same spot鈥攁 small section of a mangrove-rimmed mudflat rich in fiddler crabs, which she defends against other whimbrels. For the next seven months this would be her universe while she rebuilt her reserves of fat and strength for the arduous return trip that awaits her.
About the time you read these words, Hope will be winging northwest again, retracing the thousands of miles that will bring her back to Hope Creek on the Virginia tidelands, there to gorge on still more crabs, then across the Canadian Shield to the flower-specked tundra on the Mackenzie Delta鈥攕panning the continent on a journey whose complexities, triumphs, and dangers, like those facing all migrants, grow ever more astonishing and awe-inspiring as we decipher them.