Sharp-shinned Hawk

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(New page: Image:SharpshinnedHawk.jpg '''Common Name:''' Sharp-shinned Hawk<br> '''Scientific Name:''' Accipiter striatus '''Size:''' 9.4-13.4 inches (24-34 cm); '''Wingspan:''' 16.9-22 inches ...)
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Revision as of 18:30, 6 December 2014


Common Name: Sharp-shinned Hawk
Scientific Name: Accipiter striatus

Size: 9.4-13.4 inches (24-34 cm); Wingspan: 16.9-22 inches (43-56 cm)

Habitat: North America; a resident to long-distance migrant. Sharp-shinned Hawks of the Appalachians and Western mountains may remain there year-round, whereas birds that breed in the northern U.S. and Canada leave their breeding grounds and may winter in the rest of the continental United States or migrate as far as southern Central America.

Sharp-shinned Hawks are birds of the forest and forest edge, and are not found where trees are scarce or scattered, except on migration. They require dense forest, ideally with a closed canopy, for breeding. While favoring forests that contain conifers, they also nest in stands of aspen in Colorado, oak-hickory forest in Missouri, and the hardwood forests of the East. They occupy a wide range of elevations, from sea level to near treeline. In the winter season, look for Sharp-shinned Hawks at forest edges, in somewhat more open habitats than the dense forests they breed in, as well as in suburban areas with bird feeders.

Status: Least Concern. Global population: 700,000 adult individuals. Sharp-shinned Hawk numbers appear to have remained stable from 1966 to 2010. These birds are so solitary and elusive in their deep-forest breeding sites that scientists have little data on their nesting success. However, populations estimates are able to be made from yearly migration counts. Partners in Flight estimates 49% percent spending some part of the year in the United States, 40% in Canada, and 14% in Mexico. They breed only in dense stands of trees, and so their fate is intertwined with that of wooded wilderness. Like other birds of prey, these hawks suffered breeding failure when the pesticide DDT was in use in North America. Some carry high levels of this pesticide in their bodies even today, perhaps because much of their songbird prey spends winters in South America, where DDT is still used. Sharp-shinned Hawks were once killed as vermin by bird enthusiasts trying to protect songbirds. These hawks do hunt birds at feeders, and the spread of backyard bird feeding may have helped populations of Sharp-shinned Hawks or allowed them to spend winters farther north than they used to.

Diet: Songbirds make up about 90 percent of the diet. Birds the size of American Robins or smaller (especially warblers, sparrows, and thrushes) are the most frequent prey; bigger birds are at less risk, though they’re not completely safe. They will eat small rodents, such as mice and voles, and an occasional moth or grasshopper.

They are “pursuit hunters”, often surprising their prey on the wing by bursting out from a hidden perch with a rush of speed. They are versatile: small birds may be taken in the air or on the ground; they may pounce from perches as little as 3 feet above the ground to catch rodents; and they catch some insects on the wing. Sharp-shins make great use of cover and stealth to get close to their prey, surprising it at close range rather than diving from great heights. Sharp-shinned Hawks use their long toes and talons to impale and hold moving prey. They’ve even been known to reach into wire-mesh bird traps to grab prey with their toes.

Nesting: While sexes are alike, females are 30% larger than males. Adults are slatey blue-gray above, with narrow, horizontal red-orange bars on the breast. Immature birds are mostly brown, with coarse vertical streaks on white underparts. Adults and young have broad dark bands across their long tails.

Throughout their range, Sharp-shinned Hawks favor conifer trees (pine, spruce, or fir) as nesting sites, but may also use aspens and hardwood trees. The nest is always placed under dense forest cover, usually toward the top of a tall tree, but well under the canopy. Most nests are anchored between horizontal limbs and the tree trunk. The nest is a broad, flat mass of dead twigs, usually conifer twigs, sometimes lined with flakes of bark. Both members of the pair bring nesting material to the site, but the female does most or all of the construction. The shallow, platform-like nest is usually 1–2 feet in diameter and 4–6 inches deep. The eggs and young often sit more on than in this wide, open-topped nest.

Cool Facts: The size difference between the sexes in Sharp-shinned Hawks influences the size of prey they can catch. Nestlings feed first on small prey caught mainly by their father, switching as they grow to the larger prey that their mother can bring. Before delivering prey to their mates or young, male Sharp-shinned Hawks typically remove and eat the head.

The Sharp-shinned hawk is easily mistaken for the slightly larger and lankier Cooper's hawk, which match the sharp-shinned in plumage. Female Sharp-shinned hawks approach the size of a male Cooper’s hawk. 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".

There are 4 subspecies of Sharp-shinned hawk:

  • A. s. striatus. The nominate species is widespread in North America, occurring in all of the forested part of USA and Canada, breeding in most of it. Populations in the northern part of the range migrate south and spend the non-breeding season (winter) in the southern USA, Mexico and Central America as far south as Panama, with a smaller number spending the winter in the Greater Antilles. Resident populations exist in temperate parts of the USA, Canada (in a few coastal regions), Mexico (highlands from Sonora to Oaxaca), Cuba, Hispaniola and Puerto Rico.
  • A. a. chionogaster. The white-breasted hawk occurs in highlands from far southern Mexico (Chiapas and Oaxaca), through Honduras, Guatemala and El Salvador, to Nicaragua. It is, as far as known, resident, but some local movements may occur. Resembles the members of the nominate group, but upperparts darker (often appears almost black), thighs whitish-buff and underparts and cheeks entirely white. Juveniles have darker upperparts and distinctly finer streaking below than juveniles of the nominate group.
  • A. s. ventralis. The plain-breasted hawk 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 (likely to extend into adjacent parts of Roraima in far northern Brazil, but this remains unconfirmed). It is, as far as known, resident, but some local movements may occur. It is polymorphic. The most common morph has dark grey upperparts (often appears almost black) and white underparts variably barred, shaded, or mottled with rufous or tawny-buff (extensively marked individuals may appear almost entirely rufous or tawny-buff below). Occasionally, the barring to the lower belly and flanks may appear duskier. The white morph has bluish-grey upperparts (similar to the nominate group), 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 (occasionally with slight white barring to belly and faint grey bands in tail). The underparts of the females average paler than males of the same morph. The iris is typically yellow (contra illustrations in some books), 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. s. erythronemius. The rufous-thighed hawk 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. Resembles the nominate group, but upperparts darker, streaking to underparts rufous or dusky, cheeks typically with a clear rufous patch (occasionally lacking almost entirely) and iris yellow (contra illustrations in some books). Juveniles resemble juveniles of the nominate group, but streaking to underparts typically restricted to throat and central underparts, with flanks scaled or barred (often also belly).

This 3D model is found in Songbird ReMix Birds of Prey Volume III: Hawks of the New World

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