Cooper’s Hawks and Sharp-shinned Hawks are very challenging to differentiate. The screen shot below, from Cornell Lab of Ornithology’s All About Birds Web site, shows these 2 side by side. (Click here for even more photos and explanatory remarks comparing these 2 cousins. Scroll to the “Field Marks” section around the middle of the page)
You have a chance of telling the difference between these 2 species if you see them flying. A Sharp-shinned shows very little of its head projecting beyond its wings when flying. On a Cooper’s Hawk, you can see its head more clearly stretching beyond the leading edge of its wings. This photo shows this distinctp-shion as a Cooper’s Hawk is chased by a Sharp-shinned Hawk.
This photo, from a banding station, gives you a sense of the size differential between these 2 accipiters. The Sharp-shinned is on the left; the Coop, on the right.
Cooper’s Hawks tend to be silent, except during breeding season. Probably because they nest in areas thick with trees, the pair can be heard communicating with each other using a strident ke-ke-ke-ke call. Click here and scroll down to “typical voice” to hear a clip of this call.