Species: Accipiter cooperii

Cooper's Hawk

Species

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Encyclopedia of Puget Sound

A medium-size diurnal raptor with rounded wings, a long brown/black banded tail (often rounded at the end), and a hooked bill; adult is mainly gray/brown above, barred rusty brown below, with strong contrast between dark crown and paler nape and back; immature is paler, with brown upperparts, dark-streaked whitish or buffy underparts, and white undertail coverts. Average length 36-51 centimeters, wingspan 74-94 centimeters; females average larger than males (NGS 1983).

Classification

Kingdom

Animalia

Phylum

Craniata

Class

Aves

Order

Falconiformes

Family

Accipitridae

Genus

Accipiter

NatureServe

Source:
ELEMENT_GLOBAL.20.119

Classification

Other Global Common Names

Gavilán de Cooper - épervier de Cooper

Informal Taxonomy

Animals, Vertebrates - Birds - Raptors

Formal Taxonomy

Animalia - Craniata - Aves - Falconiformes - Accipitridae - Accipiter - (AOU 1998). See Whaley and White (1994) for information on geographic variation.

Ecology and Life History

Short General Description

A crow-sized, woodland hawk.

Migration

true - true - true - Northernmost populations migratory (move north mostly March-April, southward late August-early November) but regularly present throughout most of breeding range in winter. Migrates singly or in twos or threes (National Geographic Society 1983). See Palmer (1988) for more information.

Non-migrant

true

Locally Migrant

true

Food Comments

Eats medium-sized birds (e.g., starling, thrush, quail), sometimes small birds and some up to size of adult ruffed grouse, small ground-foraging mammals, occasionally reptiles (especially in southwestern U.S.) and amphibians. Their primary food is other birds; up to 90% of its diet is composed of avian prey, with mid-sized birds such as flickers and starlings being taken preferentially (Kennedy 1980). They are frequently important predators of bobwhites and were at least formerly, before the days of factory farming, raiders of domestic fowl. These food choices have led to a great deal of persecution by humans. Additional foods include small mammals, reptiles, amphibians, and insects (Bent 1937). In the southwest and west mammals and lizards can make up as much as half the food intake (Johnsgard 1990). Young birds comprise a large proportion of the food provided to nestlings. Typically hunts from inconspicuous perch, or uses a longer searching flight. Sometimes attracted to birds at feeders. Birds may not necessarily prevail in the diet (Bielefeldt et al. 1992).

Reproduction Comments

The breeding season usually begins in early April and extends through May and June (Bent 1937, Brown and Amadon 1968). The annual molt begins in late June but can occur as late as October (Bent 1937). Southward migration commences in the northern states in late August, with September being the peak month; it is essentially over by November. Northward migration occurs from late February to early April (Brown and Amadon 1968). The male does most of the nest building and occasionally some of the incubation; most of the incubation is done by the female, which seldom leaves the nest before the young have fledged (Brown and Amadon 1968). During the pre-fledging period the male provides both the female and the young with food, while both parents feed the young for up to four weeks after they leave the nest (Brown and Amadon 1968). Only one brood is raised each year. The normal clutch is four-five eggs, with clutches of three and six being rarely observed (Bent 1937). A national average has been calculated at 3.5 eggs (Bednarz et al. 1990). Replacement clutches are laid if the first set is lost, and laying can be delayed under conditions of low food availability (Bent 1937, Snyder and Wiley 1976). Hatching success data are limited, but in areas unaffected by DDT contamination the average hatching rate ranges from about 70% to 83% (Craighead and Craighead 1956, Johnsgard 1990), with some further reduction in the brood occurring after hatching. Normal fledging success rates range from 2.1 to 3.5 for pairs with successful nests (Craighead and Craighead 1956, Schriver 1969, Henny and Wight 1972, Reynolds and Wight 1978, Herron et al. 1985); roughly 80% of nests produce at least one fledgling (Henny and Wight 1972). In areas affected by DDT poisoning these figures were reported to be dramatically reduced. The young fledge one month after hatching, the males leaving the nest three-four days earlier than the larger females. They remain dependent on their parents until they are eight weeks of age and have learned to forage on their own (Brown and Amadon 1968). Only about 19% of the birds breed in their first year. Most nest by the second year and continue breeding throughout the rest of their lives.

Ecology Comments

Few data on population densities exist. Craighead and Craighead (1956) found 1554 hectares per pair in 1947-1948 in Michigan. In Maryland a density estimate of 200 hectares per pair was calculated by Stewart and Robbins (1958). Rosenfield et al. (1991) compiled nesting densities from various studies. These densities ranged from a low of 5000 hectares per pair in North Dakota in 1987, to a high of 331 hectares per pair in a pine plantation in southeastern Wisconsin in 1986. Strongly territorial. Males vigorously defend an area 30 meters in diameter around the nest site although they may forage up to 3.2 kilometers away (Brown and Amadon 1968). Johnsgard (1990) reported home range sizes that ranged from 105 to 784 hectares (the latter was seasonal home range; daily home range was 231 hectares). Nests are typically spaced 2.4 - 5.6 kilometers apart (Brown and Amadon 1968, Reynolds and Wight 1978, Kennedy 1980, Campbell et al 1990) and not usually less than one kilometer apart (Palmer 1988). The smaller sharp-shinned hawk also appears to keep similar distances from Cooper's hawk nests (Brown and Amadon 1968, Reynolds and Wight 1978), indicating interspecific aggression probably related to competition for food. Winter range is larger. Michigan birds ranged over areas of 2.4 - 3.2 kilometers in diameter. Dispersal range is limited. In Wisconsin, six males dispersed 4 - 35 kilometers (mean 12 kilometers) from natal site to nesting site; one female dispersed 14 kilometers (Rosenfield and Bielefeldt 1992). Hunt by a combination of still-hunting and searching flights along woodland edges and natural routes (Johnsgard 1990). Birds following inland migration routes apparently migrate over longer distances than those following coastal routes, and tend to have longer wings and tails, creating lower "flight-surface loading." This is thought to be an adaptation to the longer flight distances, more open country, and stronger thermal updrafts encountered along the inland routes (Smith et al. 1990). Mortality appears to be quite high during the birds' first winter, approaching 78% as opposed to only 34% per year for the adults 2 to 8 years old (Henny and Wight 1972). The maximum recorded lifespan is 8 years (Henny and Wight 1972). Life history traits place it intermediate for population turnover rate between the larger goshawk and smaller sharp-shinned hawk. This may partially explain the slower recovery of Cooper's from a population crash in the 1950s-1960s compared to sharp-shinned hawks (Bednarz et al. 1990).

Length

Weight

529

Conservation Status

NatureServe Global Status Rank

Global Status Last Reviewed

1996-11-26

Global Status Last Changed

1996-11-26

Distribution

Conservation Status Map

ELEMENT_GLOBAL.20.119