Sharp-shinned Hawk

Appearance

This is a small ''Accipiter'' hawk and is the smallest hawk in North America. Males are 23 to 30 cm long, have a wingspan of 42 to 58 cm and weigh from 82–115 g . As common in ''Accipiter'' hawks, females are distinctly larger in size, with an average size advantage of 30%, and a weight advantage of more than 50% being common. The female measures 29 to 37 cm in length, has a wingspan of 58 to 68 cm and weighs 150 to 219 g . The wings measure 14.1–22.9 cm each, the tail is 12–19 cm long and the tarsus is 4.5–5.9 cm . Measurements given here are for the northern group, but they are comparable for the remaining subspecies. Adults have short broad wings and a long square-ended tail banded in blackish and grey . The remiges are whitish barred blackish. Legs yellowish. The hooked bill is black and the cere is yellowish. The remaining plumage varies depending on group:

⤷  Nominate group: Cap dark and upperparts blue-grey . Often, a few more or less random white spots can be seen on the back. Underparts white with rufous or tawny bars. Crissum white. Thighs rufous, but often barred white. The cheeks are tinged rufous . The irides are dark orange to red, but these are yellowish to pale orange in juveniles. Juveniles have dark brownish upperparts with each feather edged rufous, giving a rather scaly appearance. The brown head is streaked whitish, and the whitish underparts are extensively streaked brown.


⤷  ''A. chionogaster'' : Resembles the members of the nominate group, but upperparts darker , thighs whitish-buff and underparts and cheeks entirely white. Juveniles with darker upperparts and distinctly finer streaking below than juveniles of the nominate group.
⤷  ''A. ventralis'' : Polymorphic. The most common morph has dark grey upperparts and white underparts variable barred, shaded or mottled with rufous or tawny-buff . Occasionally, the barring to the lower belly and flanks may appear duskier. The white morph has bluish-grey upperparts , but its underparts are all white except for its rufous thighs. The rare dark morph, the only morph which sometimes lacks rufous thighs, is entirely sooty . The underparts of the females average paler than males of the same morph. The iris is typically yellow , but individuals with a darker iris are occasionally seen. Juveniles have dark brownish or dusky upperparts with each feather typically edged rufous, giving a rather scaly appearance. The underparts are white streaked brown, and the thighs are rufous barred white. Occasionally, juveniles with underparts extensively rufous streaked blackish are seen.
⤷  ''A. erythronemius'' : Resembles the nominate group, but upperparts darker, streaking to underparts rufous or dusky, cheeks typically with a clear rufous patch and iris yellow . Juveniles resemble juveniles of the nominate group, but streaking to underparts typically restricted to throat and central underparts, with flanks scaled or barred .* The northern group is easily mistaken for the slightly larger and lankier Cooper's Hawk, which match the Sharp-shinned in plumage. In flight, the Cooper's, with its longer wings and larger head, is sometimes compared to a "flying cross"; whereas the broader-winged and smaller-headed Sharp-shinned is described as a "flying mallet".

⤷  ''A. chionogaster'' is generally easily recognized by its white underparts. Juv. Bicolored Hawk, juv. Barred Forest Falcon and Collared Forest Falcon generally occur below the altitude of ''chionogaster'', and they have whitish or buff nuchal collars. Juv. Double-toothed Kite and certain ''Buteo'' hawks may show a vaguely similar pattern, but are very differently shaped.

⤷  ''A. ventralis'' , while itself very variable in plumage, is generally easily recognized by the ''Accipiter'' shape and the colour of the underparts. The grey underparts of the Bicolored Hawk are not duplicated by any plumage of ''ventralis'' and juv. Bicoloured has a nuchal collar. The smaller Tiny Hawk mainly occurs in lowlands, is very small and lacks the rufous thighs of ''ventralis''. The rare dark morph ''ventralis'' is arguably the plumage most likely to cause confusion with other species , but the yellow eyes and the overall shape means that it too is relatively distinctive.

⤷  ''A. erythronemius'' is distinctive within its range, but commonly confused with the Roadside Hawk . The Bicolored Hawk is the only other ''Accipiter'' within the range of ''erythronemius'' which may show yellow eyes and rufous thighs, but it has a different pattern below.

Distribution

This species is widespread in North America, Central America, South America and the Greater Antilles. Below the distributions of the four groups are described as they roughly occur from north to south:

⤷  The nominate group is widespread in North America, occurring throughout a large part of USA and Canada, except in the ice-covered regions of the far north. Populations in the northern part of the range migrate south and spend the non-breeding season in southern USA, Mexico and Central America as far south as Panama, with a smaller number spending the winter in the Greater Antilles. Resident populations exists in temperate parts of USA, Canada , Mexico , Cuba, Hispaniola and Puerto Rico.
⤷  ''A. chionogaster'' occurs in highlands from far southern Mexico , through Honduras, Guatemala and El Salvador, to Nicaragua. It is, as far as known, resident, but some local movements may occur.
⤷  ''A. ventralis'' occurs in the coastal mountains of northern Venezuela and Colombia, south through the Andes from western Venezuela, through Colombia, Ecuador and Peru, to central Bolivia. A disjunct population occurs in the Tepuis of southern Venezuela . It is, as far as known, resident, but some local movements may occur.
⤷  ''A. erythronemius'' is widespread in eastern South America in eastern and southern Brazil, Uruguay, Paraguay, north-eastern Argentina and south-eastern Bolivia. It is, as far as known, resident in some regions and migratory in others. The movements are generally poorly understood, but it only occurs seasonally at some localities in Argentina.

Status

In North America this bird declined in numbers in the 1960s and 1970s, probably as a result of the use of DDT and other pesticides. The population of USA and Canada has rebounded since and might even exceed historical numbers today. This is probably due to the combination of the ban on DDT and the proliferation of backyard birdfeeders in North America which create unnaturally reliable and easy prey for all ''Accipiters''. Migratory Sharp-shinned Hawks are one of the most numerous raptors recorded at "hawk watches" across the country. An exception is the subspecies from Puerto Rico, ''Accipiter striatus venator'', which is rare and listed as endangered by the U.S. Fish & Wildlife Service. The remaining resident subspecies from the Greater Antilles, ''fringilliodes'' from Cuba and nominate from Hispaniola, are uncommon, local, and, at least in the case of the latter, decreasing. Both ''ventralis'' and ''erythronemius'' are fairly common and presently considered safe. The situation for ''chionogaster'' is potentially more problematic due to its limited range, although it, at least locally, remains fairly common.

Habitat

It occurs in a wide range of woodland and forest types, both dominated by conifers and by various types of broad-leaved trees The largest populations of the nominate group are thought to occur in the temperate boreal forests, but winter in warmer regions further south . The taxa ''suttoni'', ''madrensis'' , ''chionogaster'' and ''ventralis'' , are found in upper tropical to temperate highlands; mainly at altitudes of 300–3000 m , but occasionally down to near sea-level and up to 4000 m . The taxon ''erythronemius'' is found in tropical and subtropical regions; both in lowlands and highlands.

Reproduction

Sharp-shinned Hawks will construct a stick nest in a large conifer or dense group of deciduous trees. Clutches of 3 to 8 eggs have been recorded, but are usually 4 to 5 eggs. The eggs measure 37.6 x 30 mm and weigh about 19 g. The eggs are prized by egg-collectors, because they are heavily marked with surprisingly colorful and varied markings. The incubation period is thought to average at about 30 days. After hatching, the young are brooded for 16 to 23 days by the female, while the male defends the territory and catches food. The young fledge at about a month old and rely on their parents for feeding and protection another 4 weeks. The nesting sites and breeding behavior of Sharp-shinned Hawks are generally secretive, in order to avoid the predation of larger raptors, such as the Northern Goshawk and the Cooper's Hawk. While in migration, adults are sometimes preyed on by most of the bird-hunting, larger raptors, especially the Peregrine Falcon. The breeding behavior of the taxa ''chionogaster'' , ''ventralis'' and ''erythronemius'' are comparably poorly known, but based on the available knowledge they appear to differ little from that of the nominate group.

Food

These birds surprise and capture all their prey from cover or while flying quickly through dense vegetation. They are adept at navigating dense thickets and many attacks are successful, although this hunting method is often hazardous to the hawk. The great majority of this hawk's prey are small birds, especially various songbirds such as sparrows, wood-warblers, finches, wrens, nuthatches, tits, icterids and thrushes. Birds caught have ranged in size from a 4.4-g Anna's Hummingbird to a 577-g Ruffed Grouse and virtually any bird within this size range is potential prey. Typically, males will target smaller birds, such as sparrows and wood-warblers, and females will pursue larger prey, such as American Robins and flickers, leading to a lack of conflict between the sexes for prey. These hawks often exploit backyard bird feeders in order to target congregations of ideal prey. They often pluck the feathers off their prey on a post or other perch. Rarely, Sharp-shinned Hawks will also eat rodents, lizards, frogs, snakes, and large insects.