For as long as I have been a birder people have been posing the question: Is it a Sharp-shinned Hawk or a Coopers Hawk? These two bird-catching Accipiters are perennial patrons of backyard bird feeding stations, drawn not to the seed but the seed-eating birds you have concentrated there.
Don’t despair and don’t presume that you are the cause of some sparrow’s demise. We egocentric humans love to presume a pivotal role in all the world’s unfoldings. The fact is by feeding birds in your yard you are not causing them to be killed by bird-catching hawks, you are only causing them to be killed where you will see them. Your neighborhood bird-catching hawk is going to feed somewhere at least once a day, more often in cold weather. Get used to it. It’s a little like watching lions and zebra on the nature channel except it’s real. But the question persists: which accipiter species is working your feeder?
Probability says Coopers Hawk. This, the larger of the two species, is a common breeder and winter resident in New Jersey. In fact a pair probably nest in your neighborhood woodlot.
The other reason the odds say Coopers is because Cooper’s Hawks eat Sharp-shinneds and over the course of the winter, any Sharp-shinned working your feeder stands a good chance of being returned to earth as a regurgitated Coopers Hawk pellet. This is good news for chickadees and titmice, birds that are generally too nimble and small for Cooper’s Hawks to target, thus another clue.
If the hawk at your feeder is catching Mourning Doves and feral pigeons odds are it’s Cooper’s Hawk. Sharp-shinned Hawks target smaller species from Blue Jays to chickadees.
As for plumage traits. Both adult and juvenile Coopers show a broad and crisply defined bright white terminal band on the end of the typically well rounded tail. Sharp-shinneds show a narrow diffuse band on a square cut tail that is difficult to see.
Adult Cooper’s Hawks show a distinct blackish cap that does not blend into the dark back, in fact is separated by a pale hindneck. Also when alert, Cooper’s hawks raise the hackles on their head, giving the bird a peak-headed appearance. Sharp-shinneds never raise their hackles. Juvenile Coopers have all dark brown heads contrasting with lightly streaked pale breasts, so appear hooded. Further, the brown heads of juvenile Coopers are tinged with orange giving the heads a warm brown tone. A juvenile Sharp-shinned’s head is cold brown. Structurally, Coopers have a large bill and a sloping forehead giving them a “Roman-nosed,” appearance.
One last behavioral observation. Coopers Hawks are prone to sit out in the open, often on isolated, exposed perches, like fence posts. Sharp shinneds tend to stay concealed—almost never perch out in the open away from cover.