Saturday, March 23, 2013

Cooper's Hawk

Cooper's Hawk - Accipiter cooperii

The quick agile accipiters also include the Sharp-shinned and Northern Goshawk.

The bird is named after William Cooper, a hunter who supplied ornithologists with specimens during the early 19th century.

The female is larger than the male, an example of sexual dimorphism, an attribute perhaps related to the large size of the eggs.  

The short rounded wings of the accipiters are well-adapted for quick maneuvering in dense forests. Falcons and Buteos are not capable of the bursts of weaving flight through dense brush. If the prey is not taken after a short chase, the pursuit is ended. Surprise, not endurance, is the hallmark of an accipiter.  

Cooper's Hawks breeds throughout the southern half of the Rockies. The hawks migrate according to a timetable set by the movements of their passerine prey. Passerines are taken on the wing and the hawk usually takes the prey to a "plucking" site prior to eating. 

I have never identified a Sharp-shinned Hawk. However, I have identified a Cooper's Hawk on 16 occasions in my Discovery Rise backyard. Since differentiation of these two accipiters is notoriously difficult, perhaps some of the Cooper's, might be Sharp-shinned.  

The chart above shows the months when a Cooper's Hawk was identified in my backyard. Not unexpectedly, the most sightings were in May, a month with very high passerine traffic at my feeders. I have not identified a Cooper's Hawk in November, January or February. Perhaps their migration takes them south during the winter.  


The Atlas of Breeding Birds of Alberta. Federation of Alberta Naturalists. 2007.

Baicich PJ, Harrison CJO. Nests, Eggs, and Nestlings of North American Birds. Princeton UP. 2005.

Dunne P, Sibley D, Sutton C. Hawks in Flight. Houghton Mifflin Co. Boston. 1988.

Fisher C, Acorn J. Birds of Alberta. Lone Pine Publishing. Edmonton. 1998.

Sibley David A. The Sibley Guide to Bird Life & Behavior. Alfred A Knopf, Inc. New York. 2001.

Scotter GW, Ulrich TJ, Jones EJ. Birds in the Canadian Rockies. Prairie Books. Saskatoon. 1990.

Tudge Colin. The Bird. Crown Publishers. New York. 2008.

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