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.
| 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) |
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).
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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).
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