Which came first - the chicken or the eagle?

In a twist on the age-old question, chickens are being used to hatch the eggs of birds of prey at the Raptor Rehabilitation and Propagation Project Inc.The wildlife research center in southwestern St. Louis County is home to dozens of predatory birds, some of which were brought to the center after being injured and are being rehabilitated for return to the wild.

The Raptor Project also includes breeding programs for various birds of prey, or raptors. Researchers at the center say they are relying on non-predatory birds - a flock of chickens, to be exact - to help hatch the eagles, falcons, owls and hawks.

"We've been using chickens here for a long time to incubate our eggs," Walter Crawford Jr., ornithologist and executive director of the Raptor Project, said Wednesday.

"We also have the fancy mechanized incubators, but when you get down to the nitty-gritty, chickens seem to do the best job for us."

Taking the eggs away from their natural parents within seven to 10 days of being laid encourages the raptors to lay more eggs than they would if they had to sit on the eggs until hatching.

After several years of using Cochin bantam hens as surrogate mothers, the research center has developed a flock of chickens that really seem to enjoy their work. Crawford said the breed has the best temperament for the job and are easy for the humans to work with.

"They're very broody," he said. "You can walk in there with a golf ball and they'll jump right on it."