Cooper’s hawk (Accipiter cooperii) is a medium-sized hawk which goes by several common names, including big blue darter, chicken hawk, hen hawk, Mexican hawk, quail hawk, striker and swift hawk. Cooper’s hawk is native to North America. A member of the goshawk genus Accipiter, it was first described by French naturalist Charles Lucien Bonaparte in 1828. The bird was named after the naturalist William Cooper, one of the founders of the New York Lyceum of Natural History and later the New York Academy of Sciences in New York.
Accipiter cooperii is found from Southern Canada to Northern Mexico.
Cooper’s hawks have short rounded wings. The wing chord measures 8.4 to 0.9 inches long. It has a relatively long tail, 6.7 to 8.1 inches long, with dark bands, round-ended at the tip. As in most accipiters, the tarsus is relatively long, measuring 2.2 to 3 inches, and the bill is relatively small, with the culmen from the cere measuring only 0.59 to 0.83 inches. Adults have red eyes and have a black cap, with blue-gray upper parts and white underparts with fine, thin, reddish bars. The tail is blue-gray on top and pale underneath, barred with black bands. Immatures have yellow eyes and have a brown cap, with brown upper parts and pale underparts with thin black streaks mostly ending at the belly. The tail is brown on top and pale underneath, barred with dark bands. The eyes of this hawk, as in most predatory birds, face forward, enabling good depth perception for hunting and catching prey while flying at top speeds. They have hooked bills that are well adapted for tearing flesh of prey. Immatures are somewhat larger than a sharp-shinned hawk and smaller than a northern goshawk, though small males nearly overlap with large female sharp-shinned hawks, and large female Cooper’s hawks nearly overlap with small male goshawks. Cooper’s hawks appear broader-chested and larger-headed than sharp-shinned hawks, with generally more robust features.
The Cooper’s hawk appears long-necked in flight and has been described by birdwatchers as looking like a “flying cross”. The Cooper’s hawk is seen mostly flying with quick, consecutive wing beats and a short glide, though they may also soar.
As in many birds of prey, the male Cooper’s hawk is smaller than the female. The birds found east of the Mississippi River tend to be larger on average than the birds found to the west.
The average mass of an adult male ranges from 7.8 to 15.5 ounces with a length between 14 and 18 inches. The adult male is significantly smaller than the average female, which weigh 12 to 25 ounces and measure 17 to 20 inches in length. Its wingspan ranges from 24 to 37 inches. Individuals living in the eastern regions, where the genders average 12.3 ounces and 20.0 ounces, tend to be larger and heavier than those in the western regions, where the respective genders average 9.9 ounces and 16 ounces.
Their breeding range extends from southern Canada to northern Mexico. They are generally distributed more to the south than the other North American accipiters, the sharp-shinned hawk and the northern goshawk. Birds from most of the Canadian and northern U.S. range migrate in winter, and some Cooper’s hawks winter as far south as Panama.
The Cooper’s hawk occur in various types of mixed deciduous forests and open woodlands, including small woodlots, riparian woodlands in dry country, open and pinyon woodlands, and forested mountainous regions. They now nest in many cities. They were once thought to be averse to cities and towns, but are now fairly common urban and suburban birds, especially those cities which provide plenty of rock pigeon and mourning dove for the Cooper’s hawk to prey on.
Although adaptable in habitat, studies have indicated that the species still more often than not prefers sizeable tracts of woodland for breeding and migrating to fragmented, developed areas.
These birds capture prey by stealth, moving from perch to perch in dense cover, listening and watching, then putting on a burst of speed to overtake prey. They sometimes cruise low over ground, approaching from behind shrubbery to take prey by surprise. This is a dangerous hunting style. Some 23 percent of 300 Cooper’s hawk skeletons investigated revealed healed fractures in the bones of the chest. Cooper’s hawks prey almost exclusively on small to mid-sized birds. Typical prey species include American robins, other thrushes, jays, woodpeckers, European starlings, quail, icterids, cuckoos, pigeons and doves. Birds preyed on can range in size from wood-warblers to ring-necked pheasants. They may also prey upon the raptor American kestrel and other smaller raptors, including their cousin the sharp-shinned hawk. They have been known to rob nests and may supplement their diet with small mammals such as chipmunks, hares, mice, squirrels, and bats.Even more rarely, they may prey on lizards, frogs, or snakes. A raptor normally catches its prey with its feet and kills it by repeatedly squeezing it and holding it away from its body until it dies. They have also been seen drowning their prey, holding it underwater until it stops moving. The hawks often pluck the feathers off their prey on a post or other perch. They also hunt songbirds at backyard feeders, perching nearby and then swooping down and scattering the birds to single one out in flight. They may pursue prey on the ground by half running and half flying.
Cooper’s hawks are monogamous, but most do not mate for life. Pairs will breed once a year and raise one brood per breeding season. Courtship displays include stylized flights with the wings positioned in a deep arc. During their flight displays the male will begin by diving toward the female. A slow speed-chase follows, involving the male flying around the female exposing his expanded under tail coverts to her. The male raises his wings high above the back and flies in a wide arc with slow, rhythmic flapping. Courting usually occurs on bright, sunny days, in midmorning. After pairing has occurred, the males make a bowing display before beginning to build the nest.
Their breeding habitats are forested areas. The breeding pair builds a stick nest in large trees. Over a two-week period the pair builds the nest. The nests are piles of sticks around 28 inches in diameter and 5.9 to 6.9 inches high with a cup-shaped depression in the middle that is 8 inches across and 4 inches deep. Their nests are built in pines, oaks, Douglas firs, beeches, spruces, and other tree species, usually on flat ground rather than on a hillside. The nests typically are between 25 to 50 feet high off the ground, halfway up the tree, and out on a horizontal branch. The male feeds the female for up to a month before she begins laying eggs.
The clutch size is usually 3 to 5 eggs. The cobalt-blue eggs average about 1.9 inches × 1.5 inches and weigh about 1.5 oz. The female incubates the eggs between 30 and 36 days.The hatchlings are about 0.99 ounce and 3.5 inches long and are completely covered in white down. They are brooded for about two weeks after they hatch by the female, while her mate forages for food. The male brings food to female, and then incubates for a few minutes while female is eating. The male brings food, gives it to the female at perch near nest, and she feeds it to young. Young may climb about in nest tree after about 4 weeks, and can fly at about 4-5 weeks, with the fledging stage being reached at 25 to 34 days of age, though the offspring will return to the nest to be fed until they become independent around 8 weeks. Eggs and nestlings are preyed on, rarely, by raccoons, crows as well as other competing Cooper’s hawks. Adults rarely fall prey to larger raptors, namely red-tailed hawks, great horned owls, peregrine falcons, golden eagles, and northern goshawks.
Cooper’s hawks communicate using vocalizations and displays. Vocal is probably preferred over display, because the denseness of their habitat could prevent displays from being seen from a distance. Males are usually submissive to females and will listen for reassuring call notes the females make when they are willing to be approached. The males have a higher pitched voice than females.
Cooper’s hawks live as long as 12 years in the wild. The oldest known Cooper’s hawk was 20 years and 4 months old.