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It’s happened more than once, but I’m still not used to it: looking down from my dining room window as a Cooper’s hawk flies up the driveway. The driveway seems to be a transit corridor, part of the bird’s (or birds’) hunting territory. The effect—a feathered projectile hurtling past the kitchen window—would be even more startling from ground level. 

We think of hawks as creatures of the wild, but some have adapted handily to city life. Urban areas can serve as breeding or wintering grounds for them. 

I first discovered the local pair of Coopers nesting in a venerable elm a few blocks away. I was concerned for them when the elm succumbed to disease and was taken down, but the hawks relocated to a sweetgum around the corner. I’ve also had a plausible report of a pair nesting south of the UC campus, and others may be around. Their nests are easy to spot in winter, until the trees leaf out and give the hawks some privacy while they incubate their eggs and rear their young. But you can still watch the traffic in and out of the nest tree, and listen to the adults’ nasal “Kek kek kek” calls. 

Cooper’s hawks are the midsize model of the trio of North American accipiters, about crow-sized; smaller than the northern goshawk, larger than the oddly-named sharp-shinned hawk. The Cooper in question was a 19th century naturalist, co-founder of the New York Lyceum of Natural History. To traditionalist falconers, these three species would be true hawks (as opposed to falcons, buzzards, harriers). They’re specialist bird hunters, built for close pursuit of mobile targets in woods and thickets: long-tailed, short-winged avian fighter planes. 

Splendid birds that they are, I’ll admit to some ambivalence about having Cooper’s hawks in the neighborhood. Since they prey on other birds, I’d wondered if I was in fact provisioning a hawk-feeder when I put out seed for the songbirds in my yard. Coopers can handle sizable prey like pheasants, crows, teal, even smaller raptors. But wouldn’t they also take advantage of the smorgasbord of finches and sparrows attracted to bird feeders? 

A recent study by biologists Timothy Roth III and Steven Lima, published in The Condor (the journal of the Cooper Ornithological Society, a group named for the son of the hawk’s namesake) suggests the story is more complicated than that. Roth and Lima set out to document what kind of prey Cooper’s hawks hunted in an urban setting, and how they went about it. Their study area was Terre Haute, Indiana, which, dissimilar as it may be to Berkeley in most respects, does sustain its own population of wintering hawks. 

Roth and Lima live-trapped 13 Cooper’s hawks during two successive seasons and rigged them with radio transmitters. The devices had position-sensitive mercury switches that signaled whether a hawk was perched in its normal upright posture, waiting for something to happen, or in a horizontal pose as it plucked and ate whatever it had killed. The researchers shadowed the hawks daily until early spring and reported that the birds “were unperturbed by the presence of humans in vehicles or other urban disturbances.” 

The hawks turned out to have two main hunting modes. Sometimes they waited in ambush until a smaller bird got within close striking range. But they also used what Roth and Lima called “contour-hugging attacks,” flying a few feet above the ground and using buildings, fences, and vegetation to cover their approach to stationary prey, with a final burst of speed as they came in for the kill. It sounds like this is what’s going on with the hawks that use my driveway. 

The birds in the study often lost visual contact with their targets during these broken-field runs, but seemed to know where they were headed. And the chase was not always triggered by sight of the quarry: Four hawks staged surprise attacks on empty feeders, which must have been productive in the past. It appears the hawks were using fairly sophisticated mental maps to maneuver through their territories. 

As for what they were after, the Terre Haute Cooper’s hawks concentrated on starlings, mourning doves, and feral pigeons. These three species constituted 95 percent of the hawks’ targets. Although ubiquitous, house sparrows tended to be ignored. Sex has some effect on prey size, though. As in many raptors, female Coopers are larger than males. The one male in the study did go after the occasional sparrow, but seemed to prefer bigger game. Roth and Lima suggest that the small fry were just not worth the effort it would have taken to catch them. 

That’s the Cooper’s, though. Its smaller cousin, the sharpshin, takes proportionally smaller prey, and is a definite threat to sparrow-sized birds. But Coopers seem to exclude sharpshins from their hunting territories; only a few sharpies were observed in the Terre Haute study, most at the periphery of the Coopers’ turf. This seems prudent on the smaller hawks’ part. Coopers, remember, will prey on other raptors. To a big female Cooper’s, a small male sharpshin would look a lot like lunch. 

So if you’re within the cruising range of one of Berkeley’s resident Cooper’s hawks, you should be able to keep stocking your feeders without too much guilt about turning your backyard finches into hawk bait. In an indirect way, the small birds may actually benefit from the predators’ presence.