ANN ARBOR—The Thanksgiving holiday brought more out-of-town visitors than just Aunt Marge and Uncle Joe. According to University of Michigan Building Services, Ann Arbor’s annual black-feathered, noise-making visitors have returned for yet another winter.

The American crow (Corvus brachyrynchos) can be found all over the country in flocks containing up to hundreds of thousands of birds, said Cynthia Parr, U-M zoology researcher. Flocking in such large numbers may help the crows locate additional food sources and help with breeding. But why ANN ARBOR—

“Why not? There are lots of tall trees, few predators, warm and well-lit buildings,” said Parr. According to her research, about 10,000 crows grace Ann Arbor with their presence each winter. They are coming from neighboring farms and from Canada. The warm buildings drive back the cold night air, and the bright lights make it easier to spot both predators and prey.

Ann Arbor crows can be a nuisance, said Parr, but they’re not a health threat. Their feces is bothersome, but not a danger. “There is also no reason to be concerned about crows striking people who walk near the roost. The only cases I know of where crows flew at and hit humans involve birds defending nests—and even then crows are almost always too afraid of people to get close,” said Parr.

The crows may not be dangerous, but they are annoying, says U-M pest specialist Dale Hodgson, who has worked with Parr on the crow problem in Ann Arbor for the last three years. “The crows mainly stay around Angell Hall, the Diag, South State Street and the Barbour-Newberry dorms,” said Hodgson. “This gets to be a huge problem for the students in those dorms, who don’t appreciate all the cawing, especially at night and around finals.”

To combat this problem, Hodgson fires “what is essentially a flare gun” into the air. The noise and the light aggravates the flock, which eventually leaves. “They don’t like to be harassed, and, if you do it enough, they’ll pack up and go, for a while. Persistence is the key.”

Hodgson believes that there is one big flock of crows in Ann Arbor, who start in the cemetery, and wind up on central campus. According to Hodgson, the flock will likely leave around mid-March, or as soon as the weather starts to warm up. “It’s strange,” he said. “Four years ago, we had no real crow problem. The next year, we did, and we have no idea why.”

EDITORS: Contact Parr at csparr@umich.edu and Hodgson at (734) 647-4118 or via e-mail at daleh@umich.edu

csparr@umich.edu