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

Accipiter striatus Vieillot
Sharp-Shinned Hawk
Family: Accipitridae

Species account author: Jamie Fenneman

© Tom Munson  Email the photographer   (Photo ID #9705)


Distribution of Accipiter striatus 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 grayish flight feathers; in flight, the flight feathers show narrow darker banding. The relatively long, square-tipped tail is grey above and paler below, with several broad dark bands and a narrow whitish tip. The underparts are whitish with dense, extensive rufous barring on the breast, flanks, and belly; the undertail coverts are white. The underwing coverts are densely barred with rufous and are similar in colour to the underparts. The crown and nape are grey or blue-grey and are similar in colour to the upperparts or slightly darker. The cheeks are rufous-brown and the throat is whitish or washed with rufous. 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 tips. Often shows irregular pale buffy patches on 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 the adult, but is brownish rather than grey. The underparts are whitish with extensive dark brownish or rusty-brown streaking on the breast and belly, merging with dark barring on the sides and flanks; the undertail coverts sometimes show dark brownish streaking. The crown and nape are brownish with fine darker streaking, and the cheeks and sides of the neck are paler (or even whitish) with dark brown streaking, often with a brownish wash on the ear coverts. There is often a whitish line above the eye, but this can be obscured in particularly dark individuals; the throat is whitish, often with fine dark streaks. The iris is yellow, but bare part colouration (bill, legs, feet) is otherwise similar to the adult.

Measurements
Total Length: 25-36 cm (f > m)
Mass: 93-192 g (f > m)

Source: Bildstein and Meyer (2000); Taylor (2006).

Biology

Identification

Very similar to Cooper’s Hawk in all plumages and often difficult to identify. The Sharp-shinned Hawk is a smaller, chunkier hawk and the Cooper’s Hawk often appears noticeably more slender and lanky, but this can be difficult to discern without extensive familiarity with both species. Further complicating factors, the sizes of large female Sharp-shinned Hawks and small male Cooper’s Hawks approach each other, making some intermediate-sized individuals particularly confusing. In flapping flight, Sharp-shinned Hawks generally have quicker, choppier wingstrokes than Cooper’s Hawks, and the wings of soaring/gliding Sharp-shinned Hawks are typically pushed slightly forward with the head hunched in the recess of the leading edge between the wrists. In contrast, the leading edge of the wings in Cooper’s Hawks is usually straighter with the head appearing to protrude noticeably.

The shape of the tail is the most commonly used feature to separate these two species of Accipiter. In the Sharp-shinned Hawk, the tail is slightly shorter and is noticeably squared at the tip (visible both when perched as well as in flight). In contrast, the Cooper’s Hawk has a relatively longer, more slender tail that is rounded at the tip, although individuals of both species that are missing some tail feathers can have confusing tail shapes. Other features used to separate these two species include the more distinct and contrasting dark crown of adult Cooper’s Hawks (more or less lacking in Sharp-shinned, which has a wholly gray crown that is the same colour as the upperparts) and the usually denser and heavier streaking and barring on the underparts of juvenile Sharp-shinned Hawks (juvenile Cooper’s Hawks typically have sparser, finer, and neater streaking on the whiter underparts, although some particularly pale juvenile Sharp-shinned Hawks can approach the appearance of typical juvenile Cooper's Hawks). Minor supporting field marks include the relatively larger eye that is more centrally-placed on the head and the thinner tarsus of Sharp-shinned Hawks.
Vocalizations

Most commonly heard call is a rapid, high-pitched, and thin kik-kik-kik-kik or kek-kek-kek-kek. This call is similar to a call given by the Cooper’s Hawk, but is noticeably higher-pitched and possibly faster. This call is given primarily during the breeding season and serves as communication between both members of a breeding pair. The male’s voice is slightly higher-pitched than that of the female. The male occasionally gives a single kip contact call when arriving at the nest which is often answered with a flatter, longer kep or keep call from the female. Perched birds also give a plaintive squealing call during courtship. During defense of the nest or pursuit of a predator, sometimes gives a ricky-ricky-ricky alarm call.

Source: Bildstein and Meyer (2000).

Breeding Ecology

Courtship
Poorly known. Courtship displays often include both individuals of a pair soaring and circling above a nest site at sunrise, interspersing flapping flight with gliding flight, and occasionally partaking in exaggerated undulating flight with alternating shallow and steep dives followed by a recovery to original height. Both individuals call intermittently during these flight displays. This sunrise display is often accompanied by one individual of the pair tucking its wings and plummeting towards the ground, recovering only just above the canopy of the forest; this plummeting display typically ends the courtship display period, which last for 3-20 minutes.

Nest
Nests are notoriously difficult to detect due to the secretive nature of the species during the breeding season and dense, forested habitats that it chooses for nest sites. Nest building apparently begins shortly after arrival on the breeding grounds. Individuals commonly return to a nest site during subsequent years, but reuse of the actual nest is rare. The nest is a broad (60-65 cm across), flat (15 cm high), untidy structure that is composed of coniferous twigs and often lined with finer twigs and strips of bark. The nest is usually placed on a large limb and against the trunk, typically within a relatively dense area of foliage but well below the crown. The old nests of birds or squirrels are sometimes used as a base for the nest. It is most commonly placed in a conifer, even when most of the surrounding forest is composed of deciduous species, but deciduous trees are also chosen on occasion. Rarely, nests are placed in the hollow of a tree trunk or a cliff crevice. It is placed at a height of (2.4) 4-12 (19) m.

Eggs
Clutches of (3) 4-5 (8) eggs are laid between late May and early June and the incubation period is (30) 34-35 days. Both sexes incubate the eggs, and most eggs have usually hatched in B.C. by mid-July. The smooth, non-glossy eggs are dull white to pale bluish-white and are usually lightly and variably speckled with brown or purplish markings that are often concentrated towards the ends or middle of the egg. This species produces only one clutch per year.

Young
Following hatching, the young remain in the nest for 23-25 days (slightly longer for females). The nestlings are semi-altricial and downy, with short creamy-white or yellowish-white down when very young and pale purplish-buff to whitish down when slightly older, sometimes with some grey on the back. The nestlings are tended solely by the female, although the male brings food back to the nest for both the female and nestlings when they are very young. Dates for nestlings in B.C. range from early July to mid-August, but some nestlings may occur as early as late June. The young are able to fly at 23 days of age but are tended by the parents for 21-28 days after fledging.

Source: Campbell et al. (1990b); Baicich and Harrison (1997); Bildstein and Meyer (2000).
Foraging Ecology

The Sharp-shinned Hawk is a small hawk that relies primarily on avian prey, particularly small woodland-inhabiting or brush-inhabiting passerines such as warblers, sparrows, blackbirds, wrens, and thrushes. The range of avian prey consumed also includes such unlikely species as hummingbirds, grouse, shorebirds, and Marbled Murrelets, but none of these species are very important in the diet of this species anywhere in its range. It often concentrates around residential bird feeders as an easy source of prey. This species will also occasionally consume small mammals such as mice, voles, chipmunks, squirrels, and pocket gophers, as well as large insects such as moths. This species commonly hunts from concealed perches or during low flights, and relies on stealth, speed, and surprise to capture prey. In flight, it employs a series of quick, choppy wingbeats interspersed with short glides in a fashion that is typical of the genus Accipiter. Most pursuits are sudden and fast, and the hawk usually abandons the chase quickly if the prey is not captured.

Source: Bildstein and Meyer (2000).

Habitat


Like other species of Accipiter, this small hawk is closely associated with forested habitats throughout the year, especially during the breeding season. Breeding habitats include a wide variety of fairly dense mixed and coniferous (rarely deciduous) forest, types from lowlands to subalpine elevations, and it is commonly associated with riparian habitats during the breeding season. Some studies have shown that breeding birds tend to occur in younger, denser forests than breeding Cooper’s Hawks nearby. Wintering birds are more widely dispersed across the landscape and occupy a greater diversity of habitats, although they are rarely found far from at least some trees and tend to avoid higher elevations. Besides forests of all types, wintering habitats also include woodland edges, shrub thickets, agricultural lands, hedgerows, beaches, and many semi-urban and residential areas (suburbs, cemeteries, parks, golf courses). During fall migration, migratory individuals often occur in alpine areas along ridge tops and peaks where they can take advantage of the abundance of updrafts and thermals. Migratory birds commonly follow coastlines, lakeshores, and rivers.

Source: Campbell et al. (1990b); Bildstein and Meyer (2000).

Distribution

Global Range

Widespread breeder across northern North America, from Alaska east to Newfoundland and south to the Appalachian Mountains in eastern North America. Breeds widely throughout western North America and south into Mexico and northern Central America (Guatemala, Honduras). Isolated populations also occur in the Caribbean (Cuba, Hispaniola) and South America. Winters widely from southern Canada south to Panama.
BC Distribution

Breeding
Widespread but generally uncommon breeder throughout B.C. Somewhat less common along the coast than in the interior of the province.

Winter
Uncommon in winter along the coast (including all islands) and at low elevations in the south-central interior (Okanagan Valley, Thompson-Nicola Basin, etc.). Rare elsewhere across the southern interior east to the Rocky Mountains and sporadically into the central interior (Prince George, Bulkley Valley, etc.). This species is most commonly encountered in winter in the Georgia Depression and the Okanagan Valley.

Migration and Vagrancy
Widespread and fairly common spring and fall migrant across the entire province, and it is often the most abundant migrant raptor at hawk watch sites throughout the province. Spring migration begins in southern portions of the province in late March and continues through mid-May (peaking in late April). In northern B.C., spring migration peaks somewhat later (May). Fall migration commences in late August and continues through late October, with peak movements in early September (southern interior) or early October (south coast).

Source: Campbell et al. (1990b).

Conservation

Population and Conservation Status

Apparently secure in British Columbia, and neither the species as a whole or any of its subspecies are considered “at risk” in the province (B.C. Conservation Data Centre [CDC]) or across Canada (COSEWIC [Committe on the Status of Endangered Wildlife in Canada]). Declines in eastern North American between the 1940s and 1970s were attributed to DDT use, but the species has rebounded following the ban on DDT and is now more common in eastern North America than in the west.

Source: Bildstein and Meyer (2000).

Taxonomy


Ten subspecies of A.striatus are recognized, two of which occur in British Columbia. The B.C. subspecies are only weakly defined and not reliably differentiated in the field, and they are not recognized by all authors. Some of the neotropical forms are quite distinct (e.g., “White-breasted Hawk”, A.[s.] chionogaster) and may represent distinct species.

The two subspecies in B.C. are as follows:

Accipiter striatus velox (Wilson)
This is the most widespread and common form throughout B.C., and occupies virtually all of the species’ range in the province (except the Queen Charlotte Islands and possibly areas of the northern mainland coast). It averages slightly paler than perobscurus. Populations breeding in western North America, which have sometimes been separated as subspecies "pacificus", may average slightly more rufous on the underparts than populations elsewhere, but these differences, if they exist at all, do not appear to warrant subspecific recognition.

Accipiter striatus perobscurus Snyder
Breeds on the Queen Charlotte Islands and possibly the northern mainland coast; some individuals winter along the coast at least as far south as Oregon. This subspecies is slightly darker than velox, especially in juvenal plumage, with the underparts noticeably darker and with reduced white on the belly and thighs.

Source: Bildstein and Meyer (2000); Wheeler (2003); Pyle (2008).

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)
COSEWIC
NativeS5B,S5NYellowNAR (May 1997)
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) 2017. 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: 10/12/2017 6:00:36 PM]
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