A glance out the window reveals a peaceful scene: A flock of sparrows forages on the ground, a cardinal cracks seeds at the safflower feeder and several woodpeckers chip away at shelled peanuts and suet. Suddenly, all the birds are gone, departing in a flash of wings, all except one small downy woodpecker huddling against a suet cage.

What just happened? Somewhere out there was a Cooper's hawk, causing a sense of panic among the feeding birds. As potential prey, they see or sense hawks much more quickly than humans do, and fleeing works well as a defense strategy.

Unlike many other raptors, these crow-sized hawks don't usually hunt mammals but instead are experts at catching and eating birds. If you've ever found a pile of feathers under an arbor or back-yard tree, chances are that it was a used as a "plucking post" by a Cooper's hawk before consuming its prey.

Built for speed

Most of this hawk's diet is made up of birds. They're built to fly at top speed through the forest, changing direction in an instant in pursuit of their prey. A Cooper's doesn't give up easily, staying right on the tail of its prey until the bird somehow escapes or the hawk has it in its talons.

Skilled as they are, Cooper's hawks still only manage to capture their prey about a third of the time, and for juveniles the success rate is even lower. The birds I see most often in my back yard are youngsters, as indicated by their yellow eyes. Adult Cooper's hawks have piercing red eyes, and it's an eerie feeling to have them trained on you, something that songbirds must feel even more keenly.

Radio transmitters attached to the backs of wild Cooper's hawks revealed that starlings, mourning doves and pigeons made up 95 percent of their diet (pursuing and catching a bird requires a lot of energy and a larger bird means a bigger caloric payoff). But smaller birds, foraging in a flock on the ground or perched at feeders, don't know this. They only know that a dangerous hawk is in the area, which is why they scatter.

They also flee when a blue jay shrieks a warning that danger is near, but blue jays "cry wolf," quite often and may only want other birds to leave so they can dominate bird feeders.

Sneak attacks work best

Cooper's hawks are most successful when they hide within a tree or shrub and then fly out after a bird. They're also known to follow the contours of a landscape to cover their movements until the last second. More than a few times a Cooper's hawk has streaked down our lengthy driveway, hugging the car parked there, in hot pursuit of a starling.

What are these forest birds doing in the city?

"Cooper's hawks have adapted well to urban development, especially with an increased avian food supply available to them," says Lori Arent, clinic manager at the Raptor Center. "Bird feeders offer a daily buffet for the hawks and support them through the breeding season as they raise up to five chicks in a single clutch."

It might even be safer to hunt within cities and suburbs: The Cornell Lab of Ornithology studied more than 300 Cooper's hawk skeletons and found nearly a fourth with healed-over fractures of chest bones, caused by "tearing through cluttered tree canopies."

It's tough being a bird, even a hawk, and only about a fourth of Cooper's hawks survive their first year. It's also tough to learn to catch other birds, even though youngsters watch their parents as they hunt. Arent says adults will even flush birds from cover so their young can try to catch them on their own.

More and more Cooper's hawks are nesting in cities and suburbs. So the next time all the birds in your back yard suddenly disappear, take a look for a large, lurking bird perched nearby.

St. Paul resident Val Cunningham, who volunteers with the St. Paul Audubon Society and writes about nature for local, regional and national newspapers and magazines, can be reached at valwrites@comcast.net.