Numerous migratory species that breed in the United States and Canada are in decline, said C. Page Chamberlain, a Stanford professor of geological and environmental sciences and co-author of the Science paper. It is unclear, however, whether these loses are due to problems in their breeding grounds in the north or their wintering habitat in the Caribbean.

According to the National Audubon Society, Central America, which plays winter host to as many as one-third of all North American migrants, lost about 2.3 million acres of forest cover per year between 1990 and 1995. Haiti and other Caribbean islands also have suffered widespread deforestation, which conservationists suspect is partly responsible for declining bird populations in Appalachia and other parts of North America.

To develop successful conservation strategies, you need to know where the birds go in winter, he added. Our study is the first to link southern wintering and northern breeding populations of a migrant bird.

Black-throated warblers

In the their study, the researchers analyzed minute chemical traces of carbon and hydrogen in the feathers of black-throated blue warblers (Dendroica caerulescens) a species that breeds in the eastern United States and Canada in the spring, then flies south to winter in various Caribbean islands including Cuba, Puerto Rico and Jamaica.

Dustin Rubenstein a Ph.D. student in ecology at Cornell University and lead author of the Science study analyzed feathers and developed the statistical model used in the study while he was an undergraduate at Dartmouth working with then faculty co-advisers Chamberlain and Richard T. Holmes
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Contact: Mark Shwartz
mshwartz@stanford.edu
650-723-9296
Stanford University
7-Feb-2002