In the field guides, the two hawks compliment each other nicely, with big female Sharpies reaching a length (14 inches) and wingspan (27 inches) identical to that given for a small male Coopers. An examination of typical body weights, however, points out a significant difference between the two. A big female Sharpie can tip the scales at around 8 ounces, while the more solidly-built male Coopers can weigh around 14 ounces. A little 6-ounce Sharpie male might be regarded as prey by both sexes of Coopers, especially by the females, which can run as large as 21 inches long and 20 ounces in weight.
Studies have indicated that Sharp-shins feed almost entirely upon birds, usually around the size of a warbler or sparrow. The Coopers will prey upon small birds, but typically prefer larger prey in the size range of quail, starlings and doves. The Sharp-shin is commonly a bane of the backyard bird feeder, while each winter we have Coopers in town associated with our large blackbird and starling roosts.
Cooper’s Hawks are also much more likely to take mammals, with around 20 percent of their diet consisting of mammals up to the size of small rabbits and squirrels. Although they may sometimes seem invincible, both these hawks suffer a degree of mortality similar to that of their prey. A majority of the juveniles do not survive long enough to breed and very few adults survive past five years of age.
In North America, Sharp-shins typically nest in coniferous woodlands, being common in the north woods to the limit of the tree line and at higher elevations further south. Although there is much range overlap between the two species, Coopers are typically associated with broadleaf forests and can be found in more open areas than the Sharpie, breeding across most of the lower 48 states, southern Canada, and the highlands of Mexico. In areas of range overlap up north, the Sharp-shin arrives on the breeding grounds as much as a month later than does the Coopers, timing its breeding cycle to coincide with that of its songbird prey.
Although it has a somewhat limited breeding distribution in the continental U.S., the little Sharp-shin has one of the largest breeding ranges of any of our raptors. Cuba and Puerto Rico both have their own resident races, and Sharpies of various descriptions can be found breeding down to the highlands of Central America, and again on south along the Andes clear down to Argentina.
In our area, both species are listed on the county checklist as uncommon in winter, and generally turn up in only single digits on the local Christmas count. I see both often enough that I suspect they actually occur in numbers comparable to such winter visitors as Kestrels but are commonly under-counted due to their secretive habits.
The numbers of both Accipiters seem to me to increase in the spring, the last of the Sharp-shins passing through in May. A pair of Coopers has bred locally in recent years on Camp Bullis, and I suspect a few others breed within the county, possibly within the city limits.
~Mike Scully
Illustrations by Julie Zickefoose, from Bird Watcher’s Digest, September/October 1999 - Vol. 22 No. 1: “Identify Yourself: The Accipiters” by Erik A. T. Blom
