Bedford Audubon Society

The Accipters—
Sharp-shinned Hawk, Cooper's Hawk, and Northern Goshawk
By Tait Johansson

Each fall, ridge tops throughout the northeastern United States play host to flights of migrating hawks. The most spectacular of these in our area are the flocks of Broad-winged Hawks that pass through in mid September. But providing the most consistent flight throughout the fall hawk-watching season are the three species in the genus Accipiter, the Sharp-shinned Hawk (shown at left), Cooper’s Hawk, and Northern Goshawk. A steady stream, rather than a flood like that of the Broad-winged Hawks, the accipiter migration stretches from late August into November, with a peak in early to mid October. Catching updrafts above ridges, migrating accipiters are often more easily seen closely than other, higher-soaring hawks. The bulk of our accipiter flight is made up of Sharp-shinned Hawks, with significant numbers of Cooper’s, and a smattering of Northern Goshawks.

The accipiters, the so-called “true hawks,” are structurally adapted for pursuing and catching other birds, and this distinctive structure allows the hawk watcher to identify them as members of this genus. All three accipiters, relative to other birds of prey, have long tails and short, rounded wings. This combination of traits enables these hawks to maneuver through trees and brush after their prey, the long tail acting as a rudder that lets them change direction abruptly, and the bluntness of their wings makes it possible to fly through smaller spaces in the foliage more easily.

Telling the three species apart is usually much harder than identifying a bird as an accipiter. Sharp-shinned Hawks and goshawks will seldom be confused, simply because they differ so greatly in size—sharp-shins range from the size of a Blue Jay to slightly bigger, and Northern Goshawks are about the size of a crow or larger. The main problem is telling the intermediate-sized Cooper’s Hawk from the other two, and this can be very difficult. Even experienced birders make mistakes, and sometimes at fairly close range. Some general guidelines for telling Sharp-shinned and Cooper’s (the two most commonly encountered species here) apart are as follows: on average, Sharp-shinned Hawks have a squared-off or notched tail tip, while Cooper’s Hawks have a rounded end to the tail. When soaring, Sharp-shinned Hawks also show a slight bend in the leading edge of the wing, while the Cooper’s holds the leading edges of its wings straight. This difference in soaring posture gives the Cooper’s a stiff, rigid look, “like a flying cross,” subtly different from the Sharp-shinned’s more curved wing posture.

Further, there is often a difference in the manner in which the two species flap their wings, although using this trait for identification requires much comparative experience with the two species. The Cooper’s Hawk tends to have a stiffer-winged appearance when it flaps compared to the Sharp-shinned, with less movement of the “wrists” of the wings.

One good site in the area for viewing this flight is the hawk-watching platform at the Nature Conservancy’s Butler Sanctuary on Chestnut Ridge Road in Bedford. Whether you become (or already are) an expert in accipiter identification, or are content to let most of them rocket by you unidentified, the autumn migration of these bold hunters is something not to be missed.

Photo of Sharp-shinned Hawk Courtesy of and Copyright © by Arlene Ripley

Photo of Cooper's Hawk Courtesy of and Copyright © by Rick Paris
rick@rickparis.com   www.rickparis.com

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