For the birds: Cooper’s Hawk

Thursday, May 26, 2011

Adult Cooper's Hawk. Photo by Terry Olmsted.
By Christine Southwick

Which local hawk is considered one of the bird world’s most skillful flyers?

Want a hint? Which hawk flies so fast through tree canopies in its pursuit of other birds, that approximately 23% of those hawks have fractured their wishbones at one time or another? If you said the medium-sized accipiter named after the New York naturalist, William Cooper, you should pat yourself on the back.

Adult Cooper's Hawk on nest.
Photo by Kim McCormick.
Cooper’s Hawks are monogamous, and usually mate for life. They build their nests mid-way up in tall, usually deciduous trees on bottom land, not hillsides, and lay a clutch of 3-5 cobalt blue eggs. The male feeds the female while she sits on eggs for a little over a month, and he helps bring food until the young are fully fledged. During the eight weeks that the young are being taught to hunt, they will continue to use the nest.

The females are much larger than the males, and bring down larger prey, sometimes as large as pheasant or hares. They were once called “Chicken Hawks” and were frequently shot due to the mistaken belief that they fed on chickens. Research has found that they almost never eat domestic animals.

Being hunted is no longer their greatest danger.  Now, loss of habitat is.

Though they hunt in more open areas than Sharp-shinned Hawks, they require mixed or deciduous forests for breeding. This habitat aids their hidden-approach and surprise-attack which makes their hunting so successful, and enhances clutch success.

Juvenile Cooper's Hawk.
Photo by Doug Parrott.
Telling Cooper’s Hawks from Sharp-shinned Hawks can be tricky, and even experts can be fooled. Compared to Sharpys, the Cooper’s legs are thicker—a judgment that often fails me, since I never see Sharpy and Cooper’s side by side. 

Cooper’s Hawks do have large feet and a large head relative to their body size. Another good field mark is that their body is a uniform width, unlike the Superman build of the Sharp-shinned. If it’s an adult, and in good light, the back of the head is darker, giving a hooded look. The Cooper’s will also raise its hackles, making it look fierce. And, if you can see a perched hawk’s tail, remember: Cooper’s is curved; Sharp-shinned is Square.

In the end, you may have to say it was an unidentified accipiter, and just enjoy the speed and nerve of a hawk if it visits your bird feeders for a much needed meal.

Christine Southwick is on the Board of the Puget Sound Bird Observatory and is their Winter Urban Color-banding Project Manager. She is a National Wildlife Federation Certified Wildlife Habitat Steward, having completed their forty hour class. We're happy that she's sharing her expertise with us about the birds in our backyards.

1 comments:

Anonymous,  May 29, 2011 at 5:57 AM  

Engagingly written, thanks!

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