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What is Causing Decline in Shore Birds? Scientists Use Satellite Transmitters to Find Answers

WhimbrelSeveral species of shore birds that migrate along the Atlantic Coast are in decline, including whimbrels, whose numbers have fallen by half over the last two decades.  Whimbrels are large shorebirds with long, curved beaks, spindly legs, and brown and white striped heads.

In an effort to discover what is killing so many shore birds, scientists with the Center for Conservation Biology at the College of William and Mary and Virginia Commonwealth University are working with other researchers to attach satellite transmitters to whimbrels.

Bryan WattsThe biologists are following a whimbrel they named Hope from Virginia’s lower Eastern Shore up to Canada, where whimbrels nest before flying thousands of miles back to South America.  One scientist is making an epic journey via airplane, helicopter, and motorboat in pursuit of Hope as she migrates up to the arctic, and you can learn more and follow the bird's progress by clicking here or here.

On a recent evening, Dr. Bryan Watts, Director of the Center for Conservation Biology, watched from a wooden pier as a cloud of whimbrels rose from spartina grass on Virginia’s lower eastern shore.

Pier sprung to lifeAround him, thousands of fiddler crabs darted in and out of borrows in the mud flats.  As the sun set, the night was transformed by songs from the sky.   Even the rickety platform Smith stood on seemed to magically spring to life-- with bright green leaves erupting from the pier’s posts, which are gum tree trunks driven into the salty creek.

The whimbrels approached in  formation.

“There’s a ‘V’ of whimbrels,” Dr. Watts said. “They are probably about 300 feet off of the marsh, and they are moving straight up the seaside here.  So these birds are taking off here and this is the last time they’ll touch ground until they reach the breeding grounds.  These birds will be in Toronto tomorrow morning.  And that’s almost 500 miles away.”

Whimbrels stop over on the Atlantic coast for about three weeks during their annual migration from South America to Canada and Alaska, where they nest and breed.  They visit the salt marshes of Virginia to feast on fiddler crabs until their weight nearly doubles.

But Dr. Watts and his colleagues have noticed something disturbing during their annual counts and aerial surveys of the birds.  The number of whimbrels declined by half from 1994 to 2009, according to a paper that Watts and fellow researcher Barry Truitt of The Nature Conservancy published in the journal Waterbirds.

And it’s not just whimbrels that are declining, Dr. Watts said.  Populations of sandpipers, black-bellied plovers, dowitchers, red knots, and other shore birds that migrate along the Atlantic are also falling, Dr. Watts said.

“What’s so confusing about it is that so many species are in decline,” Dr. Watts said. “And these species use different resources.  They winter in different areas…. It either suggests that there is a large factor, like global warming, for example, that may be affecting them all in slightly different ways.  Or maybe there is some common factor like hunting.”

Hunting for whimbrels and most other shore birds has been illegal in the U.S. since the passage of the Migratory Bird Treaty Act of 1918, which stopped the slaughter of birds for feathers to decorate hats. But the protections were never adopted by the Caribbean islands of Barbados, Guadeloupe and Martinique, among other countries.  And recreational hunting on these islands could be a growing problem, Dr. Watts said.

Climate change in the arctic could be distrupting whimbrel reproduction by allowing shrubs and trees to cover the open tundra and wetlands the migratory birds need for nesting. Or perhaps global warming is causing insect population booms at the wrong time for the arrival of migratory birds, Dr. Watts said.

To find clues to solve the mystery of the disappearing shorebirds, Dr. Watts’ colleagues have attached satellite transmitters to whimbrels.

Fletcher SmithBiologist Fletcher Smith (right) netted the large whimbrel that he nicknamed Hope, and he and project partners with The Nature Conservancy and other groups and agencies have been following the bird’s travels via computer.  And now that Hope and her fellow whimbrels have taken off for the North, Smith plans to hop a plane and chase Hope up to Canada, to see where she’s nesting and attach transmitters to more birds.

Smith describes his epic travel plans in pursuit of the bird. “I’m flying into Yellowknife (Canada), and then taking a twin prop up to the high arctic, and then helicopter out to the field site,” Smith said. “And then I’m taking a zodiac boat to try to find Hope on the McKenzie River.”

Perhaps the researchers will find that the satellite-tracked birds can no longer nest in a transformed arctic, or winter in Brazilian mangrove forests that are being clear-cut for shrimp farms. Perhaps the birds’ signals will wink out near hunting lodges in the Caribbean.

The scientists are determined to find answers by following Hope to the ends of the Earth.

By Tom Pelton

Chesapeake Bay Foundation

UPDATE: Biologist Fletcher Smith sent an email from Yellowknife, Canada, today (May 30) with this new information about his pursuit of Hope the whimbrel. "She is currently on the move and likely at her breeding site by now," he wrote. "You can track Hope at the following website and there is more background information at the website."   

(Photo at top of whimbrel from iStockphoto. Other photos by author)



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Virginia Beach did something to thin out the population of Canada Geese in March. Since then, there are NO gulls on the water behind my home where there were once hundreds. All other populations of different species also disappeared, although they are slowly coming back. I suspect these are birds that are moving into the area to take the place of the ones that are missing. What do you think happened?

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