Cooper's Hawk (Accipiter cooperii)

Cooper's Hawk is our mid-sized woodland raptor which uses stealth and powerful flight thrusts to attack other birds and small mammals.  It will sometimes attack from behind shrubbery, but often hunts from a perch, remaining still until it strikes.  Its size puts it between the Sharp-shinned Hawk and the Northern Goshawk, two other members of the genus Accipiter , the Latin name for a bird of prey, derived from accipere , "to take" (Clark & Wheeler).  Cooper refers to William C. Cooper (1798-1864), an American zoologist for whom the bird is named (Holloway).

Despite that fact that it is common in our area, the Cooper's Hawk can be difficult to see.  It is often seen from a distance, in flight or very briefly, and because it closely resembles the Sharp-shinned Hawk identification can be very difficult.  Further complicating identification there is great variation in the size of Cooper's Hawks (See the statistics above).  Females are about one-third larger than the males and this species exhibits "among the greatest reversed size dimorphism of any of the world's hawks" (Curtis, et al).  Some small males are the same size as some female Sharpies.

There are two plumages: adult and juvenile.  The adult Cooper's Hawk is blue gray on the back and has a dark cap which contrasts against the lighter colored nape.  This cap distinguishes the Cooper's from the Sharpie.  The head can look quite flat when the hackles on the crown are raised.  The undersides have rufous barring (horizontal) and the undertail coverts are white.  Adult Cooper's have an orange or red eye.  The juvenile is brown with brown streaking (vertical) on the undersides.  Young Cooper's have a yellow eye.  When in flight the Cooper's head looks large and protrudes beyond the elbows of the wings.  The Sharpie's head is smaller and usually extends only slightly past the wing.

Cooper's Hawks breed in the northern United States and southern Canada in conifer and deciduous forests and woodlands.  Both sexes build the nest with sticks and line it with pieces of outer bark. Generally 3-5 eggs are deposited 2-3 days apart and incubation lasts about five weeks.  The eggs hatch in the order in which they were laid, so the first born has an advantage for survival.  First flights begin after 3-4 weeks, but parents continue feeding up to 7 weeks. The birds are very tolerant of human changes to the environment and are now found nesting in urban areas and introduced trees.  Overall, the population has grown in the past 20 years.

Cooper's Hawks employ the typical accipiter flight pattern of flap-flap-flap and glide but in short bursts they can gain speed very quickly.  Their long tail helps them maneuver among trees while flying at high speeds.  You can see this flight in a video at the Macauley Library: http://macaulaylibrary.org/video/flashPlayer.do?id=7536

  References available upon request at amccormick@eastsideaudubon.org .