Winter is a great time for viewing raptors, especially in Colorado. For instance, it’s the only time of year you can see some species, like the Rough-legged Hawk or Merlin. And with the leaves off the trees, it’s much easier to see birds of prey. I’ve been seeing tons of raptors myself over the last few months, but I wanted to talk about two of them that get a lot of people (including me!) confused: the Sharp-shinned Hawk and the Cooper’s Hawk.
The Sharp-shinned Hawk and Cooper’s Hawk are both members of a group of hawks called the Accipiters. Accipiters, also known as forest hawks, are much smaller than soaring hawks like the Red-tailed Hawk. They have long tails and broad wings to help them maneuver quickly and easily through trees. In addition to forests, though, you can often find Sharp-shinned and Cooper’s Hawks in your backyard because they primarily feed on birds and small rodents.
Both the Sharp-shinned and the Cooper’s Hawks are slate grey on the back as adults, with rusty, barred breasts and grey and black striped tails. When fully mature, they also both have red eyes. Juveniles are also difficult to distinguish since they’re both brown with streaked breasts. The Sharp-shinned Hawk is the smallest Accipiter in North America, but while it’s easy to tell size differences between it and the Cooper’s Hawk if the two are sitting side by side, it’s much harder to judge size otherwise. So what other information can we use?
One often-cited id clue is to look at the hawk’s tail from the back. If the tail is rounded, you’re looking at a Cooper’s Hawk. If it’s squared off, it’s a Sharp-shinned Hawk. This is a helpful diagnostic characteristic, but not always reliable depending on molt, how the hawk is holding its tail, etc. So I’d use this as a secondary key.
I’d say the most important characters to look for in all plumage stages are the size and shape of the head and the shape of the body. The Sharp-shinned Hawk has been called “pigeon-headed” because it has a small (relative to its body), rounded head like a dove or pigeon. In flight, its head barely sticks out past the crook of its wing. By contrast, the Cooper’s hawk has a more proportionally-sized head that’s maybe a little squarish, and a longer neck. The nape of the neck on the adult Sharp-shinned Hawk is also the same color as the top of the head, making it look like it’s wearing a hood, while the adult Cooper’s Hawk has a paler nape making it look like it’s wearing a cap.
The Sharp-shinned Hawk, true to its name, also has much thinner legs than the Cooper’s Hawk and looks “squashier.” Its shorter neck makes it look noticeably broad-chested. The Cooper’s Hawk, however, is much slimmer, with a barrel shape (the same width all the way down). If you’re looking at a young hawk, you can also use the streaking on the breast as a field mark. The Sharp-shinned has much thicker streaking than the Cooper’s.
So, given what you now know, which hawk do you think this is?