Cooper's Hawk

Accipiter cooperii

by Damian Fagan

I try to ignore the horse flies digging into my flesh as I walk slowly down Courthouse Wash in Arches National Park, a vast and spectacular collection of natural sandstone arches located in east-central Utah. Though the air is cool on this July morning, the canyon will be an oven by mid-day. I wear my National Park Service uniform – gray poplin shirt and green cotton pants – since I am on duty, searching for the Coop.

The Coop is not a fugitive or a lost hiker. The Coop doesn’t really want to be found, and when I do find it, it voices its displeasure. Resembling a laughing maniac, the Coop is not some psychopath, but a small bird of prey in the Accipiter family whose “attitude” elevates its stature.

Range and Distribution

Though Cooper’s hawks (Accipiter cooperii) are common nesters here in the Southwest, their breeding range covers most of the lower 48 continental states plus southern Canada and Mexico. Although the birds are migratory throughout their range, they may be found year-round in most states except for the northern Midwestern and Northeastern states. They are more common in the West.

At western hawk migration stations in Utah, New Mexico, Oregon and California, the Cooper’s hawk is the most common species observed. They winter throughout the continental states and into Mexico and Latin America to Costa Rica.

Shape and Size

The Coop is a medium-sized raptor closely related to sharp-shinned hawks and northern goshawks. Adult birds have short, broad wings and long tails for navigating through woodlands and thickets. The back is bluish-gray on adult males and more brownish-gray on adult females. The large, square-shaped head has a dark cap and lighter nape (back of the head). The hooked beak is dark with a lighter colored cere or waxy membrane that covers the upper portion of the bill and contains the nostrils.

Cooper Hawk

Eye color changes with age from yellow to orange and then to red. The belly and breast have reddish-brown crosshatched markings, similar to those of the adult sharp-shinned. Immature birds have longer wings and tails than the adults, and the undersides have brown streaks that extend down the breast but not so much on the cream-colored belly. The backs of both sexes are brownish. The tail has a rounded tip and alternating bands of dark and grayish feathers.

The average measurements of adult male and female Cooper's hawks fall in the following ranges:

	Females	Males
Body Length	16-19 in.	14-16 in.
Wingspread	31-36 in.	27-30 in.
Weight	16-24 oz	10-14 oz

Adapted from Clark & Wheeler A Field Guide to Hawks of North America

In Flight

cooper hawk

The overall appearance of a Cooper's hawk in flight is that of a long-tailed and short, broad-winged bird. Because of size differences between the sexes and age groups, as well as the overall similarity to the related sharp-shinned hawks and northern goshawks, in-flight identification can be challenging. To distinguish a Cooper's hawk from another Accipiter, one must use plumage, size and flying characteristics to identify the species. Sometimes a distant view or quick look may not reveal sufficient clues to identify the bird, but don’t feel inadequate. Even the experts have trouble identifying these birds.

cooper hawk
A Young Hawk

Identifying marks for a Cooper's hawk in flight include size and flying characteristics. Their large head projects beyond the leading edge of the wings, thus enabling the bird to turn its head to look to the side. By comparison, the sharp-shinned hawk, with a head set slightly back from the leading edge, must tip its wings to look to the side. Though both species have rapid wing beats, the Cooper’s is a bit slower and shallower, and the Coop has a steadier flight than the Sharpie in strong winds. Cooper’s tend to alternate periods of soaring with punctuations of rapid wing beats, but don’t rely on this one habit. Also, Cooper's hawks tend to have a more rounded tail than a sharp-shinned hawk, but again this is not a foolproof character. Immatures tend to have longer tails and broader wings than do the adults, helping increase mobility in flight. This may be compensation for the young bird’s inexperience in flying and chasing prey.

Habitat Preference

Here in Arches National Park, the Cooper’s nest in the riparian zones along streams and desert washes. All of the Cooper’s nests within the park are in cottonwood trees, but at higher elevations outside the park, the birds will use aspen, ponderosa pine, Douglas fir and other trees. In Arizona and New Mexico, they will also select sycamores and oaks for nest sites.

The birds construct a large nest built of cottonwood twigs and juniper Cooper Hawk bark in an upper fork of the tree in April or May. Nests may be reused either in successive or alternate years, but often a new nest is constructed. Within a nesting territory, there may be several constructed nests, some left in various states of disrepair or abandoned due to insects, diseases or rotted limbs. I have often found ants in nests when I visited them to band young or survey for prey.

Today’s summer visit is to check on the status of the developing young, the nestlings, at three nest sites, in traditional nesting territories, in the lower portion of the canyon. The birds are fairly easy to locate because of their “madman laughing call,” a dead giveaway for this perch and pounce hunter.

The call is a rapid repetition of harsh notes that resemble the old laughing machine in my hometown’s pizzeria, sort of a cross between Jack Nicholson and a hyena. The Sibley Guide to Bird Life and Behavior describes the call as “a series of flat, nasal, barking notes pek, pek…” Whenever I hear this call I know the nest site is in the vicinity; if I’m too close, the laugh is usually punctuated with a warning flight that just barely misses my head. Welcoming committees Cooper's hawks are not.

I try to locate the bird’s nest visually during this onslaught. If need be, I move farther away to a protective location where I set up a spotting scope and am far enough away to allay the Coop’s concern. The young often hunker down in the nest while the adult (mostly the female) is squawking and driving out the intruder (me, in this case). As things settle down, I keep an eye on the nest to look for movement. It is easy to sex the nestlings; the females are larger than the males. To make up for this inequality, the males may hatch a couple of days before the females, and they may fledge from the nest prior to the females. Of course, some young don’t survive for a variety of reasons, for instance, starvation, deformity, predation or falls from the nest.

After a 28- to 30-day incubation period, the young hatch. They will take about 30 days to fledge. After fledging, they still depend on their parents for food for the next four to six weeks. Sometimes the young may be located by their food-begging calls once they are out of the nest.

The adults often hunt by perching and waiting for prey. This “perch and pursue” technique suits the quick speed and maneuverability of the birds in dense woodlands or thickets. Sometimes a bird will be observed crashing into a thicket, only to reappear moments later with prey in its talons. Some will go to a “plucking post” where feathers are torn from the prey before it is brought to the nest. When the young are older they will gobble down chunks of meat presented to them by the parents. Even if the young survive the nest period, a high percentage of them will starve to death their first year.

The birds also hunt on the wing, flying low and using cover to surprise prey. Since they prefer wooded areas, birds observed in open locations may be migratory.

Like all raptors, the Cooper's hawk will cough up a pellet comprised of indigestible parts— feathers, fur, bones or scales. By dissecting these pellets, ornithologists can determine the prey species taken by these birds.

Sexual Dimorphism

Most young Cooper's hawks are easy to sex when there are several in the nest. The females are larger than the males – a condition called “sexual dimorphism,” which means “two forms” – but the males develop quicker than the females. That is to make up for any advantage lost for their initial smaller size. The sexual dimorphism allows the adults to take a wide variety of prey. The female hunts larger birds like flickers, jays and doves, while the male takes sparrows, starlings and other smaller birds. Both will catch lizards or rodents. In some areas, mammals may make up a higher percentage of the Cooper’s diet than birds.

I often encounter plucking areas – represented by the lifeless piles of feathers from some unlucky prey – along the wash. Sifting through one pile I find the red tail feathers of a flicker and the white-tipped tail feathers of juncos.

Name and Description

The Cooper's hawk is named for William Cooper (1798 to 1864), a New York naturalist who collected specimens of the hawk, which Charles Lucien Bonaparte used in officially naming and describing the bird. Cooper named and described the evening grosbeak in 1825, and later on became the first American to join the London Zoological Society.

At one time the Cooper's hawk was known as the “chicken hawk” for its common predation on poultry. Other names include quail hawk, swift hawk, big blue darter, and striker – all defining the Cooper’s preference for birds, or of their swift nature. Gunned down because of this predation, these hawks are threatened by illegal shooting, pesticide accumulation and habitat loss.

Class Aves
Order Falconiformes
Family Accipitridae
Species Accipiter cooperii

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