PROVIDENCE, R.I.--The early bird gets the worm. The smart bird snares the berry.
A new study by a Brown University researcher suggests that many songbirds migrating south each autumn may switch from typical meals of insects to a berry-rich diet to store sufficient fat to fuel their grueling migration. The study also shows migrating songbirds seek out fruit-laden "refueling" sites where they can fill up on berries for the long haul.
The Brown study indicates that these "pit stops," which are under intense development and ecological pressure, are extremely important to many species of tiny songbirds that travel thousands of miles every fall from breeding sites in the United States and Canada to wintering grounds in Latin America and the Caribbean.
"Many researchers and bird watchers knew that North American migrating birds consumed fruit during autumn, but the extent and importance of that shift wasn't clear," said Jeffrey Parrish, author of the study. "There has been a huge gap in our knowledge about the biological processes of songbirds during migration and how those activities might affect the recently reported declines in their numbers."
During three fall migrations on Block Island, R.I., Parrish and volunteers netted 7,000 songbirds and analyzed more than 1,600 of their droppings to determine their diets. In reports to be published in Studies in Avian Biology and tentatively accepted for publication in The Condor, Parrish found that a dietary switch from insects to fruit occurred to some degree in the majority of the 69 species sampled. Several species followed diets that contained more than 80 percent fruit.
Most migrants--the hermit thrush, red-eyed vireo and yellow-rumped warbler,
for example--ate berries primarily. The fruits of native shrubs, including
northern arrowwood, bayberry and pokeweed, contributed the majority of fruit
consumed. Only a few species of birds, such as the American redstart, remained
on strictly
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Contact: Scott Turner
Scott_Turner@Brown.edu
401-863-2476
Brown University
12-Sep-1996