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Where Finches Sleep

"All we wanted to know was whether House Finches roost in large groups at night," says André Dhondt, director of Bird Population Studies at the Lab. The question was simple, but it generated several years of intensive field work and raised even more questions.

"We suspected that a large group huddling close together would make it easier for House Finch eye disease (mycolasmal conjunctivitis) to spread from bird to bird," says Dhondt, who heads the Lab's House Finch Disease Survey. "We were amazed by what we found."

A male House Finch with a radio transmitter that aided researchers in locating the bird at night. The researchers recapture the finches and remove the devices after three weeks.

Andy Davis

Dhondt and fellow researchers attached radio transmitters to nine groups of House Finches in Ithaca, New York, to help locate the birds at their roosts. They expected to find large, permanent roosts, based on previous studies of finch behavior. Instead, they found just a few birds at each roost. They also found that the sites were temporary, established wherever the finches were foraging at the time. They published their results in the July 2007 issue of Ibis, the journal of the British Ornithologists' Union.

"Northeastern finches may have altered their roosting behavior," says Dhondt, "because they have a reliable, predictable source of food from backyard feeders." A study of roosting habits among House Finches in other parts of the country would be needed before scientists can say with certainty that the birds have changed their behavior throughout their North American range—but Dhondt suspects they have.

Other surprises from this study include the distances that finches traveled in a day (nearly two miles) and the apparent social bond displayed between some same-sex finches found roosting and foraging together during the non-breeding season.

"We've been studying House Finches for seven years," says Dhondt, "and there's still a lot we don't know about their social structure and about how eye disease spreads."

To find out more about the Cornell Lab of Ornithology's House Finch Disease Survey and how you can take part, visit

Pat Leonard


For permission to reprint all or part of this article, please contact Laura Erickson, editor, Cornell Lab of Ornithology, 159 Sapsucker Woods Rd., Ithaca, NY, 14850. Phone: (607) 254-1114. email:

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