Connecting the Dots Along Migratory Flyways
The dawn of a new era in ornithology is revealing the secrets of many species’ migratory journeys in astonishing detail. Here are some of the latest endeavors.
Scientists across Canada and the U.S., working collaboratively through the Sea Duck Joint Venture, have been tracking this little-studied group of waterfowl, which includes scoters, eiders, harlequin ducks and long-tailed ducks, many of which are experiencing population declines. Their findings have revealed the unexpected complexity of sea duck migration. For example:
o Long-tailed ducks winter all along the Atlantic coast, but those wintering near Cape Cod came primarily from breeding grounds in northern Quebec, while those using the Chesapeake Bay bred north and west of Hudson Bay. Long-tailed ducks off Nantucket came from both regions, staging in the Canadian Maritimes. With so many sea ducks in decline—and with major offshore wind projects now on the drawing board—such information will be vital to managers.
o Female black scoters showed a peculiar, dog-leg migration route—from their breeding grounds in the Northwest Territories, they fly southeast, skirting the edge of Hudson Bay to New Brunswick, then turning south along the Atlantic coast as far as Georgia.
"We found that the distances traveled during migration, the routes they took and the location of wintering grounds really varied among turkey vulture populations," says David Barber, research biologist at Hawk Mountain Sanctuary in Pennsylvania. "Only half the birds tagged in Pennsylvania migrated at all, wintering from Maryland to Florida, while West Coast birds migrated along the Pacific to Mexico and Guatemala." Those from the Canadian prairies in Saskatchewan were long-haul migrants, flying down a narrow corridor through Mexico and Central America all the way to Venezuela. Vulture populations in Asia have crashed, and Africa's are crashing; if similar problems are to be avoided in the western hemisphere, such information is critical.
These oceanic wanderers breed in Chile, where they have been tagged with satellite transmitters on the nest, then followed on migrations that may extend all the way to Alaska, tens of thousands of miles a year. The shearwaters, like an increasing number of migrants, were tagged with solar-powered transmitters; freed from the constraints of battery life, these newer tracking devices can work for years and years at a stretch, charging themselves each time the sun comes up.
Eastern golden eagles
Little had been known about this small, geographically distinct breeding population, which nests in the boreal forest and subarctic of eastern Canada; lead poisoning from spent ammunition and wolf snares are direct threats. But the biggest danger may come as they migrate down the Appalachians, along ridges under intense wind development pressure. Newly developed GSM transmitters, which communicate through cellular phone networks that are now nearly ubiquitous, allow scientists in the U.S. and Canada to track the movements of these eagles with astounding precision, and to identify travel corridors where simply moving proposed wind turbines a few hundred yards may prevent collisions.