Thousands of crows have been roosting in trees on the ISU quad this winter. (Photo courtesy of Flickr/nottsexminer)

By The Associated Press

NORMAL - Illinois State University has tried just about everything, but has not been able to stop thousands of crows from roosting on the quad this winter.

West Nile Virus took a heavy toll on the birds in 2001. Since then, however, they've bounced back, causing a nuisance.

The school has tried to scare them off with plastic owls, rubber snakes and something called pyrotronics, which are similar to bottle rockets and produce a loud bang when launched into the trees where the birds roost. That has had some effect, but more than 2,000 crows came back to roost on the quad at dusk Thursday.

ISU biological sciences professor Angelo Capparella said Friday before the pyrotronics were brought in "every single tree was just covered in crows."