Cooper’s Hawk

By Darcy Thomas

A flock of waxwings dart from their restive perches chased by an agile hunter of the sky. Within minutes they return, but their rest is brief. The winged hunter swoops in again, flushing them into the sky. The predator, in close pursuit, uses its long tail as a rudder to maneuver through the trees. It dashes and swerves. Crack! A bone has snapped in its chest as it bursts through a branch. This doesn’t slow it down. With a surge of speed, the hunter snatches a waxwing with sharp talons then flies to a perch where it squeezes the bird until it dies, then plucks the feathers. Now the hunter begins tearing flesh and the meal begins.

Cooper’s Hawks, Astur cooperii, once in the genus Accipiter, has been moved to the genus Astur as of October 2024. (For more taxonomic information please refer to https://ebird.org/news/2024-taxonomy-update).

Cooper’s Hawks are medium-sized, have broad, rounded wings and a very long tail. Adults have steely blue-gray feathers above and warm reddish bars on the underparts. Juveniles are brown above with vertical brown streaks underneath. They prey mostly on other birds and hunt both from perches and on the wing. Hunting perches are usually hidden in dense cover. They watch and wait until their prey is unaware, then swoop in low and fast to take them by surprise. When hunting on the wing they use the dense cover of trees to stealthily pursue their prey. They can maneuver through the trees by using their tail as a rudder for agile turns.  

During the breeding season, these hawks take their prey to a traditional plucking post within the breeding pair’s territory. After first squeezing the bird to death, they remove the feathers with their beak. Their bill is not notched so they are unable to kill prey with it. Sometimes they submerse and drown their prey before plucking them. When they are caring for young, both parents will cache surplus food on branches near the nest. While dependent on birds for at least 70 percent of their diet they will also eat small mammals, reptiles, amphibians, fish, and insects. 

Cooper’s Hawks often sustain injuries related to their hunting style. Coracoid bone fractures (chest bone fractures) are common as the hawks burst through tree branches after their prey. Studies show 23 percent of Cooper’s Hawks have evidence of healed bone fractures. 

During Jewel Basin Hawk Watch (JBHW) you are likely to see migrating Cooper’s Hawks. Volunteers at JBHW counted 568 during the 2024 season. Cooper’s Hawks are native to the Americas and breed from the southern parts of Canada south to northern Mexico. While some individual birds stay in their home territory year-round, birds from the northern part of their range migrate to warmer locations in the fall before winter sets in and prey becomes scarce. Some migrate as far as Central America or even Colombia. 

Cooper’s Hawks prefer deciduous woodlands with aspen, cottonwood, and box elder and will also nest in a mixed forest with stands of Ponderosa Pines and Douglas firs. During winter they hunt in open forests and even in towns. 

To tell the difference between Cooper’s Hawks and the look-alike Sharp-shinned Hawks look at their tails. Cooper’s Hawks have rounded tails while sharpies have squared off tails. Next, look at their heads. Cooper’s Hawks have larger, blockier heads than sharpies. Nape feathers on adult Cooper’s Hawks are light in color giving them the appearance of wearing a cap. Sharpie’s have dark nape feathers and appear to be wearing a hoodie. In flight, Cooper’s Hawks look somewhat like a cross-shape with their head sticking out beyond the front edge of the wings. Sharpies look more t-shaped with their small heads somewhat in alignment with the front edge of their wings.

Size can be deceiving, but generally Cooper’s Hawks are about the size of a crow, while Sharp-shinned Hawks are about the size of a Blue Jay. Females are larger than males. Learning to tell the difference between these two birds really boils down to experience. Give yourself grace and time to learn. Winter is a great time of year to view raptors and improve your identification skills. With leafless trees and the barren landscape raptors are more conspicuous. With fewer daylight hours and lower prey abundance, raptors hunt with purpose and intensity. This makes them easier to view.