E-Fauna BC: Electronic Atlas of the Wildlife of British Columbia

Accipiter cooperii (Bonaparte)
Cooper's Hawk
Family: Accipitridae

Species account author: Jamie Fenneman

© Tim Zurowski  Email the photographer   (Photo ID #7958)


Distribution of Accipiter cooperii in British Columbia.
(Click on the map to view a larger version.)
Source: Distribution map provided by Jamie Fenneman for E-Fauna BC

Species Information

Adult
The upperparts of this species are grey or blue-grey with darker greyish flight feathers; in flight, the flight feathers show narrow darker banding. The long, slender, round-tipped tail is grey above and paler below, with several broad, darker grey bands and a narrow whitish tip. The underparts are whitish but are closely and densely barred with rufous on the breast, flanks, and belly; the white undertail coverts are long and often noticeably bushy. The underwing coverts are densely barred with rufous and are similar in colour to the underparts. The nape and cheeks are grayish or grayish-brown (often washed with rufous, especially in females), contrasting with the darker gray or blackish crown and forehead and the whitish throat; individuals sometimes erect the feathers on the rear of the head, giving the head a squared or slightly peaked appearance. Females are slightly browner than males. The iris is red (orange in younger adults), the bill is dark grey with a yellow cere, and the legs and feet are yellow.

Juvenile
This plumage is held until approximately 11-16 months of age (the summer or fall of the second year). In this plumage, the upperparts are brownish with narrow paler brown or buffy edges to the feathers; the flight feathers are darker grey with paler brownish edges or narrow buffy or rufous-tinged tips. Often shows irregular pale buffy patches on the scapulars. When in flight, the flight feathers are noticeably banded with dark grey, especially below, and the underwing coverts are whitish with dark markings (similar to the underparts). The tail is similar in pattern to that of the adult, but is brownish rather than grey. The underparts (including the undertail coverts) are whitish with numerous narrow dark streaks on the breast and belly and dark barring on the sides and thighs; the undertail coverts sometimes show dark brownish streaking. The head is brownish or buffy-brown with narrow darker streaks on the crown, nape, and sides of the neck and sometimes the hint of a pale stripe above the eye; the throat is whitish with fine dark streaks. The iris is yellow, but bare part colouration (bill, legs, feet) is otherwise similar to the adult.

Measurements
Total Length: 36-51 cm (f > m)
Mass: 262-474 g (f > m)

Source: Curtis et al. (2006); Taylor (2006)

Biology

Identification

The Cooper’s Hawk is very similar to Sharp-shinned Hawk in all plumages and is often problematic to identify. It is most readily identified by tail shape and (with practice) relative size. The longer tail of Cooper’s Hawk is generally noticeably rounded at the tip (unless some feathers are missing), whereas that of the Sharp-shinned Hawk is squared or, when fanned, only shallowly rounded. Cooper’s Hawk is also a noticeably larger, more slender bird and there is little or no overlap in size between the largest female Sharp-shinned Hawks and the smallest male Cooper’s Hawks; this feature can be difficult to use for identification, though, and requires a good familiarity with the size and shape variation in both species before it can be reliable.

Other features that can be used to separate the two species include the darker and more contrasting cap on the flatter head of adult Cooper’s Hawks (dark cap lacking in Sharp-shinned, which also tends to show a more rounded head profile) and the usually more dense dark streaking and barring on the undersides of juvenile Sharp-shinned Hawks. When soaring, Sharp-shinned Hawks hold their wings pushed forward and crooked at the wrist (with the head in a slight recession along the leading edge of the wings), whereas Cooper’s Hawks hold the wings straight out with the leading edge more or less flat and the head more obviously protruding (sometimes described as a “flying cross” in shape). Sharp-shinned Hawks also have a slightly choppier flight style when in flapping flight, but this can be approached by small Cooper’s Hawks.

Large female Cooper’s Hawks are also commonly confused with the other species of Accipiter in British Columbia, the Northern Goshawk. When seen well, adult Northern Goshawks are easily identified by a combination of their extensively grey-barred underparts (rufous-barred in Cooper’s) and variable, but often obvious, white eyebrow (lacking in Cooper’s). Structurally, Northern Goshawks are significantly bulkier and heavier, with relatively longer and pointier wings and a broader tail (almost approaching a Buteo in structure and very different from the more slender Cooper’s Hawk). Juvenile Northern Goshawks are the most likely to be confused with juvenile Cooper’s Hawks, but they too have a bold white eyebrow like the adults that is, at best, only weakly suggested in juvenile Cooper’s Hawks. This field mark, combined with the large structural differences, is generally sufficient to distinguish these two raptor species in most circumstances.
Vocalizations

The male's voice is usually higher-pitched than that of the female. The most commonly heard call by both sexes is a rather flat, repeated kak-kak-kak-kak or keh-keh-keh-keh alarm call, often given near the nest when the nest is threatened. Male also gives a higher-pitched keee-keee-keee-keee. Both sexes give a short kik location note, although it is more frequently given by males. Females sometimes give a longer whaaaa call when in the vicinity of prey that is being provided by the male or near the nest.

Source: Sibley (2000); Curtis et al. (2006)

Breeding Ecology

Courtship
The Cooper’s Hawk is a monogamous breeder during the breeding season, although only a portion of these pairs re-mate during successive years. The courtship displays typically involve slow, exaggerated wingbeats alternating with gliding with the wings held in a noticeable dihedral, often with the undertail coverts flared. Following pair formation, a perched individual of either sex (more often the males) often gives a bowing display to its mate prior to nest construction.

Nest
Nest building begins in early spring, taking about 2 weeks to complete, and individuals usually rebuild the nest each year (sometimes adding onto the previous year’s nest or onto the nests of other birds or squirrels). Occasionally uses abandoned crow nests. The male does most of the nest building, although the female will contribute lining if an old nest is used. Most nests are found in coniferous trees, although some are placed in deciduous trees. The nest is a substantial (60-70 cm across), shallow (15-20 cm high), bulky platform of sticks, usually placed in the crotch of a large branch adjacent to the trunk, usually at a height of 9-15 m above the ground. It is lined with strips of bark, coniferous or deciduous twigs, and grasses.

Eggs
Clutches of (2) 3-4 (6) eggs are laid between late April and late June (mostly in May), and the incubation period is (30) 34-36 days. The last eggs have usually hatched in B.C. by the end of July. The majority of incubation is done by the female, with the male contributing only brief and infrequent periods. The smooth, non-glossy eggs are pale bluish when first laid but quickly fade to dingy white (often with a slight bluish tinge); they are rarely marked with a few pale brown speckles. This species is single-brooded, but may replace lost clutches.

Young
The nestlings are semi-altricial and downy, with short creamy-white or silky-white down and blue-grey or brown-tinged eyes. The young are tended by the female alone, although for the first three weeks after hatching the male brings food to the nest to feed both the young and the female. Following hatching, the young remain in the nest for (27) 30-34 days (slightly longer for females) before fledging. They are then tended by the female for ~3 weeks before becoming independent. Dates for nestlings in B.C. range from early June to late August.

Source: Campbell et al. (1990b); Baicich and Harrison (1997); Curtis et al. (2006).
Foraging Ecology

Like other species in the genus Accipiter, the Cooper’s Hawk specializes on avian prey. Small to medium-sized birds such as robins, jays, flickers, starlings, doves, grouse, crows, pigeons, and sparrows form the bulk of its diet, and there is a single report of this species capturing a Belted Kingfisher in B.C. It occasionally predates predates nestlings such as those of the American Robin. It rarely takes other prey such as small mammals (chipmunks, mice, rabbits, squirrels, ground-squirrels, bats), amphibians, reptiles, insects, and even fish. Urban and suburban populations of Cooper’s Hawks are often largely dependent on backyard bird feeders and urban pigeon and sparrow populations as a source of prey.

When hunting, individuals often perch for long periods of time in a concealed location watching for prey, often utilizing a series of perches within its territory over any given period. It also uses low-elevation flights to search for prey and only rarely stoops on prey from high elevation. When in flight, typically uses a series of shallow, quick wingbeats interspersed with short glides in a fashion that is characteristic of the genus Accipiter. Occasionally pursues prey on foot. This species generally relies on quick and sudden bursts of activity, often from areas of concealment, to surprise prey and is well adapted for quick flight through dense vegetation in pursuit of birds

Source: Stewart (2003); Curtis et al. (2006); Weedon (2007).

Habitat


The Cooper’s Hawk is found in a wide variety of forested and semi-open to open habitats across its range in B.C. It is well-adapted to cities, residential areas, and parks and is often the most commonly encountered raptor in these habitats. Elsewhere, it is found in both open and closed forests of all types (deciduous, mixed, coniferous) as well as in riparian corridors, shrublands, agricultural areas, hedgerows, and open grasslands where there are few trees. It is usually encountered at low to middle elevations during the breeding season and low elevations during the winter, but it regularly moves through high elevations (alpine tundra, subalpine parkland) during fall migration

Source: Campbell et al. (1990b); Curtis et al. (2006).

Distribution

Global Range

Breeds across southern Canada and most of the United States, south into northern Mexico. Winters throughout most of its breeding range, although it withdraws from the northernmost fringes, as well as south through Mexico to Guatemala and Belize.
BC Distribution

Breeding
Widespread and generally uncommon breeder across southern B.C., although it may be locally fairly common in some areas (e.g., urban areas of Victoria and the lower Fraser Valley). It breeds throughout Vancouver Island (although it is scarce away from the southeastern lowlands) and on the southern mainland coast adjacent to Vancouver Island, as well as east through the southern Coast and Cascade Mountains. It is uncommon throughout the southern interior east of the Coast-Cascade Mountains, north at least to the Prince George area (where it is scarce) and east to the Rocky Mountains; irregular during the breeding season farther north in the central interior to Williston Lake and west to the Bulkley Valley. It is rare during the breeding season in the Peace River area of northeastern B.C. but breeding has yet to be confirmed in this region.

Winter
In winter, mostly confined to low elevations on the southern coast (primarily the Georgia Depression). East of the Coast-Cascade Mountains, the Cooper’s Hawk is uncommon in winter in the Okanagan Valley but is generally rare elsewhere in the valleys of the southern interior north to Kamloops and east to the southern Rocky Mountain Trench. It occasionally lingers in winter north to the central interior (Prince George area, Bulkley Valley). Juveniles tend to winter farther north than adults.

Migration and Vagrancy
Uncommon spring and fall migrant throughout the south coast, southern interior, and central interior of the province. Some populations on the south coast and southern interior (Okanagan Valley) are resident and their populations are augmented by migrants in the spring and fall. Spring migration occurs mainly during the second half of April, while fall migration occurs from late August to early November (peaking in September). It is a casual to very rare vagrant north and west to the Skeena River and northern mainland coast throughout the year.

Source: Campbell et al. (1990b).

Conservation

Population and Conservation Status

This species has experienced several major population declines in North America over the past hundred years (especially in the east) but has undergone a substantial recovery and populations are now stable across most of its range. Its adaptation to urbanized environments has significantly assisted in its recovery.It is not recognized as a species of conservation concern by either COSEWIC (Committee on the Status of Endangered Wildlife in Canada) or the B.C. CDC (Conservation Data Centre)

Source: Curtis et al. (2006).

Taxonomy


This species is monotypic, with no recognized subspecies, although western populations (sometimes called "A.c.mexicanus") average smaller with longer wings and shorter legs, and more rapidly develop redder irises as they age; juveniles may also average heavier streaking on the underparts. Most authorities do not consider these differences, which are weak and broadly clinal, to be sufficient to warrant subspecific recognition.

Source: Curtis et al. (2006); Pyle (2008)

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)
COSEWIC
NativeS5YellowNAR (May 1996)
BC Ministry of Environment: BC Species and Ecosystems Explorer--the authoritative source for conservation information in British Columbia.

Additional Range and Status Information Links

Additional Photo Sources

General References


Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2019. E-Fauna BC: Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. [Accessed: 13/10/2019 4:50:03 PM]
Disclaimer: The information contained in an E-Fauna BC atlas pages is derived from expert sources as cited (with permission) in each section. This information is scientifically based.  E-Fauna BC also acts as a portal to other sites via deep links.  As always, users should refer to the original sources for complete information.  E-Fauna BC is not responsible for the accuracy or completeness of the original information.


© E-Fauna BC: An initiative of the Spatial Data Lab, Department of Geography, UBC