Fundación ProAves – por la conservación en el país de las aves

Why are migratory warblers in decline?

11 March, 2011


Tuesday 12 January 2010.


Scientists trying to find out why warblers are dwindling

As many as half a million tiny golden-winged warblers used to make the annual round trip flight from Latin America to the Midwest. Now, the number is down to 200,000, and an international consortium is trying to find out why.

Michigan Technological University forestry and environmental science graduate student Amber Roth is part of the Golden-winged Warbler Working Group, which seeks to understand and reverse the decline.

“Its numbers are declining sharply, and we don’t know why,” Roth said. “We don’t know where the patient is bleeding.” The group includes scientists from the United States, Canada and Colombia, and has a small grant from the U.S. Fish and Wildlife Service.

“Some of the researchers are examining the bird’s genetics, to locate genetically pure populations,” said university spokeswoman Jennifer Donovan. “Others are studying the biochemical signature in the golden-winged warbler’s feathers, which can reveal where the young birds go after their first migration. And a third group is working to connect where the birds winter … to where they breed.” Golden-winged warblers weigh about 0.3 ounce and migrate thousands of miles each way twice a year from breeding grounds in the northern Midwest to winter homes in Central and South America. They make the trip 6 to 10 times in a lifetime.

Michigan Tech has supplied nylon nets to safely capture birds for study and release.

“These are older, damaged nets that I have in my lab, and the Latin American scientists know people who can repair them so that they can be reused,” said associate professor David Flaspohler, one of Roth’s doctoral advisers. AP