Cooper's Hawk

## Description

Cooper's hawk (Accipiter cooperii ) is a medium-sized hawk native to the North American continent and found from southern Canada to Mexico. This species is a member of the genus Accipiter, sometimes referred to as true hawks, which are famously agile, relatively small hawks common to wooded habitats around the world and also the most diverse of all diurnal raptor genera. As in many birds of prey, the male 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. It is easily confused with the smaller but similar Sharp-shinned hawk.

The species was named in 1828 by Charles Lucien Bonaparte in honor of his friend and fellow ornithologist, William Cooper. Other common names for the Cooper's hawk include: big blue darter, chicken hawk, flying cross, hen hawk, quail hawk, striker, and swift hawk. Many of the names applied to the Cooper's hawks refer to their ability to hunt large and evasive prey using extremely well-developed agility. This species primarily hunts small-to-medium-sized birds, but will also commonly take small mammals and sometimes reptiles.

Like most related hawks, Cooper's hawks prefer to nest in tall trees with extensive canopy cover and can commonly produce up to two to four fledglings depending on conditions. Breeding attempts may be compromised by poor weather, predators and anthropogenic causes, in particular the use of industrial pesticides and other chemical pollution in the 20th century. Despite declines due to manmade causes, the bird remains a stable species.

## Appearance

Cooper's hawks are agile medium-sized raptors native to the North American continent. They have hooked bills that are well adapted for tearing the flesh of prey, as is typical of raptorial birds. As adults, they are a solid blue-gray color above and have a well-defined crown made of blackish-brown feathers above a paler nape and hindneck offset against their streaked rufous cheeks. Their tail is blue-gray on top and pale underneath, barred with three black bands. The adult’s underside shows a bit of whitish base color overlaid heavily with coarse, irregular rufous to cinnamon bands. Adult females may average slightly more brownish or grayish above, while some adult males can range into almost a powder blue color. As in many birds of prey, the males in this species are smaller than the females.

## Distribution

Cooper's hawks are native to North America and found from Southern Canada to Northern Mexico. These are partially migratory birds. They tend to be most migratory in the north and largely to partially sedentary elsewhere. Cooper's hawks largely migrate out of nearly all of their range in southern Canada as well as cooler parts of the Pacific Northwest, essentially all of Montana and northern parts of surrounding states, the Dakotas, the northern parts of the Great Lake states, northern New York and much of New England. These birds inhabit various types of temperate deciduous forest and mixed forest. They can also be found in forested mountainous regions, especially foothills and in conifer forests, including the extreme southern part of the taiga. They prefer to breed in open woodlands, including small woodlots, riparian woodlands in dry country, pinyon woodlands, farmlands and floodplains. Their wintering habitats include open woods, parkland and scrub areas. In Central America, Cooper's hawks can occur in the cloud forests and treeless montane grassland. They have also adapted to urbanized areas and can even nest in many cities.

## Behavior

Cooper's hawks are generally solitary birds apart from breeding and rare aggregations during migration. They are diurnal and at night take to conifers to roost, generally sleeping with their heads tucked in. Daylight hours are spent soaring, hunting, perching, preening and sunning. Cooper's hawks are mainly arboreal but may come to walk on the ground to gather nesting materials as well as to hunt. They are agile and aggressive hunters. If they see birds when flying, hunting hawks do not fly directly to them but instead circle around to available trees and bushes often perching for a few moments before launching their attack. If birds become aware of them, hawks will tend to quickly gain height in hopes of intercepting some prey. During hunts, Cooper's hawks may suddenly alight when detecting an available mammal. Sometimes, they will engage in tandem hunts with one hawk dashing around after the prey while another one waits on the other side of a tree trunk or wooded thicket. Many birds are caught when they fly around a tree where a Cooper's hawk is inconspicuously perched. They may also chase prey into the cover or from bush to bush. The typical call of Cooper's hawks is a harsh, cackling yelp. This call may be translated as 'keh-keh-keh…', males tending to have a higher-pitched, less raspy and faster-paced voice than females. When coming with food to the nest or while displaying during courtship, the male may let out a 'kik' call. The initial call of the young is a 'cheep' or 'chirrp'. Females have what is often thought of as their own hunger cry, 'whaaaa', heard especially in poorer food areas, when the male appears. However, generally, Cooper's hawks are silent outside the breeding season.

## Diet

Cooper's hawks are carnivores. Their diet mainly consists of small or medium-sized birds, but also many small mammals and, in more arid vicinities, lizards. They may occasionally eat frogs, insects, and fish.

## Reproduction

Cooper's hawks usually are considered monogamous and form pair bonds. Breeding may begin as early as February in the southern part of the range, but, for the most part, the breeding season is from April to July. During this time pairs frequently high circle together. Males perform sky-dances in which their wings are raised high over back in a wide arch with slow, rhythmic flapping, with exaggerated down strokes. Cooper's hawks breed once per year and produce one brood. They build a bulky platform nest, usually in conifers or in broad-leafed trees. Nests are often located up to 20 m (66 ft) above the ground in the main fork or horizontal branch close to the trunk. The female lays 3 to 5 pale sky blue eggs. Incubation lasts for 34-36 days mainly by the female, though the male may substitute for 10-30 minutes after he brings his mate food. Hatchlings weigh around 28 g (0.99 oz) and are covered in white natal down with blue-gray eyes. They fledge at 27-34 days (males averaging earlier), but may often return to the nest and are not fully feathered until about 50-54 days. After about 8 weeks old, the young may start to hunt for themselves, but are usually still depend on parents for food. Cooper's hawks usually first breed at 2 years old.

## Population

### Threats

The main threats to Cooper's hawks include shooting, pollutants, and the loss of habitat. Lead poisoning can sometimes threaten these birds, through lead bullets left in the dead or injured game. Most urban-related mortality for Cooper's hawks is likely to be collisions with manmade objects. These are mostly wire strikes (with or without resulting electrocution), automobile collisions and window strikes or with other parts of manmade structure while distractingly hunting.

### Number

According to the What Bird resource, the total population size of the Cooper’s hawk is between 100,000 and 1,000,000 individuals. According to the All About Birds resource, the total breeding population size of the species is 700,000 birds. Overall, currently, Cooper’s hawks are classified as Least Concern (LC) on the IUCN Red List and their numbers today are increasing.

### Ecological niche

Generally, Cooper's hawks hunt the locally common birds and probably control their populations (such as the more numerous icterids and corvids) that may without the influence of natural predation risk overpopulation and potential harm to ecosystems.

## Fun Facts

The Cooper's hawk was named in 1828 by Charles Lucien Bonaparte in honor of his friend and fellow ornithologist, William C. Cooper.

It is claimed that during breeding Cooper's hawks may utter well over 40 call variations; this would rank them as having among the most varied collection of calls recorded for any raptor.

Cooper's hawks are known as bold and aggressive predators. Given their dietary habits, these hawks bore a poor reputation well into the 20th century; they were described as "noxious", an “avian outlaw" and "a relentless tyrant and murderer of small birds". They were also described as a “bloodthirsty” “villain”.

Cooper's hawks like to look good. During daylight hours, they tend to preen while sitting on a perch about 11 times a day and may take about 1-20 minutes to do so.

Although a rare behavior, juvenile Cooper's hawks sometimes lay on their backs along a branch (or rarely the ground), apparently bathing in the sun.

When a Cooper's hawk is threatened, the bird will lower its head, raise its "crest" (capital tract), stretch out its wings, spread the tail and engage in vocalizations.