| Sharp-shinned hawk | |
|---|---|
 | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Accipitriformes |
| Family: | Accipitridae |
| Genus: | Accipiter |
| Species: | A. striatus |
| Binomial name | |
| Accipiter striatus Vieillot, 1808 | |
| Subspecies | |
A. s. chionogaster | |
 | |
Breeding Year-round Non-breeding | |
| Synonyms | |
Accipiter velox | |
Thesharp-shinned hawk (Accipiter striatus) ornorthern sharp-shinned hawk, commonly known as asharpie,[2] is a smallhawk, with males being the smallest hawks in the United States and Canada, but with the species averaging larger than someNeotropical species, such as thetiny hawk. Thetaxonomy is far from resolved, with some authorities considering the southerntaxa to represent three separate species:white-breasted hawk (A. chionogaster),plain-breasted hawk (A. ventralis), andrufous-thighed hawk (A. erythronemius).[3] TheAmerican Ornithological Society and some other checklists keep all four species conspecific.[4]
The sharp-shinned hawk is sometimes separated into four species, with the northern group (see distribution) retaining both thescientific name and thecommon name: sharp-shinned hawk (A. striatus).[3] In addition to the nominate taxon (A. s. striatus), it includes the subspeciesperobscurus,velox,suttoni,madrensis,fringilloides, andvenator. The three remaining taxa, each considered amonotypic species if split, are the white-breasted hawk (A. chionogaster;Kaup, 1852), plain-breasted hawk (A. ventralis;Sclater, 1866) and rufous-thighed hawk (A. erythronemius; Kaup, 1850). The breeding ranges of the groups are entirelyallopatric, although the wintering range of the nominate group partially overlaps with the range ofchionogaster (as is also the case with certain taxa within the nominate group). This allopatry combined with differences in plumage (seeAppearance) and, apparently, certain measurements, has been the background for the split, but hard scientific data are presently lacking (AOU). Disregarding field guides, most material published in recent years (e.g. AOU, Ferguson-Leeset al. p. 586, and Dickinsonet al.) has therefore considered all to be members of a single widespread species – but not without equivocation: Ferguson-Lees et al. say that if they were to make a world list, they would include the three taxa as separate species (p. 75), and the AOU's comment includes the note "split almost certainly good".
Storer (1952) suggested that the southernmost populations within the nominate group were paler below, thus approachingchionogaster. This has also been reflected in recent guides, whereA. s. madrensis of southern Mexico is described as being relatively pale below (compared to more northern subspecies), but if this is a sign ofintergradation withchionogaster or a north-south cline which includes both the members of the nominate group andchionogaster remains unclear. In Bolivia,ventralis and erythronemius approach each other, but no evidence of intergradation is known – something that, without actualspecimens, also would be hard to prove due to the variability in the plumage ofventralis.
A 2021 study of sharp-shinned hawks recommended recognising the three endemic Caribbean island subspecies as distinct species, based on analysis of nuclear and mitochondrial DNA and diagnosed by their plumage:A. striatus, restricted to the island of Hispaniola,A. fringilloides to Cuba andA. venator to Puerto Rico. If this is accepted andA. striatus treated as endemic to Hispaniola, the continental complex would take the scientific nameA. velox.[5]
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This is a smallAccipiter hawk, with males 23 to 30 cm (9.1 to 11.8 in) long, with a wingspan of 42 to 58 cm (17 to 23 in) and weight from 82–115 g (2.9–4.1 oz). As common inAccipiter hawks, females are distinctly larger in size, averaging some 30% longer, and with a weight advantage of more than 50% being common. The female measures 29 to 37 cm (11 to 15 in) in length, has a wingspan of 58 to 68 cm (23 to 27 in) and weighs 150 to 219 g (5.3 to 7.7 oz). The wings measure 14.1–22.9 cm (5.6–9.0 in) each, the tail is 12–19 cm (4.7–7.5 in) long and the tarsus is 4.5–5.9 cm (1.8–2.3 in). Measurements given here are for the northern group, but they are comparable for the remaining subspecies.[6] Adults have short broad wings and a medium-length tail banded in blackish and gray with the tip varying among individuals from slightly notched[7] through square to slightly rounded (often narrowly tipped white). Theremiges (typically only visible in flight) are whitish barred blackish. The legs are long and very slender (hence the common name) and yellow. The hooked bill is black and thecere is yellowish. The remaining plumage varies depending on group:
This species is widespread inNorth America,Central America,South America and theGreater Antilles. Below, the distributions of the four groups (seeTaxonomy) are described as they occur roughly from north to south:
It occurs in a wide range of woodland and forest types, both dominated byconifers and by various types ofbroad-leaved trees (especiallyoaks) The largest populations of the nominate group (see taxonomy) are thought to occur in thetemperateboreal forests, but winter in warmer regions farther south (see distribution). Thetaxasuttoni,madrensis (both from the nominate group),chionogaster (white-breasted hawk) andventralis (plain-breasted hawk), are found in uppertropical to temperate highlands; mainly at altitudes of 300–3,000 m (980–9,840 ft), but occasionally down to nearsea-level and up to 4,000 m (13,000 ft). The taxonerythronemius (rufous-thighed hawk) is found in tropical and subtropical regions; both in lowlands and highlands.
These birds surprise and capture most of their prey from cover or while flying quickly through dense vegetation. They are adept at navigating dense thickets, although this hunting method is often hazardous to the hawk. The great majority of this hawk's prey are small birds, especially varioussongbirds such assparrows,wood-warblers,finches,wrens,nuthatches,tits,icterids andthrushes. Birds caught range in size from a 4.4 g (0.16 oz)Anna's hummingbird to a 577 g (1.272 lb)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 asAmerican robins andflickers, 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, the latter typically being dragonflies captured on the wing during the hawk's migration.Bats have occasionally been recorded as a prey of this hawk.[8]
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Sharp-shinned hawks construct a stick nest in a largeconifer or dense group ofdeciduous trees. Clutches of 3 to 8 eggs have been recorded, but 4 to 5 eggs is the typical clutch size. The eggs measure 37.6 mm × 30 mm (1.48 in × 1.18 in) and weigh about 19 g (0.67 oz). 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 prey. The young fledge at the age of about a month and rely on their parents for feeding and protection another four 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 theAmerican goshawk and theCooper's hawk. While in migration, adults are sometimes preyed on by most of the bird-hunting, larger raptors, especially theperegrine falcon. The breeding behavior of the taxachionogaster (white-breasted hawk),ventralis (plain-breasted hawk) anderythronemius (rufous-thighed hawk) are comparably poorly known, but based on the available knowledge they appear to differ little from that of the nominate group
In North America this species declined in numbers in the 1960s and 1970s, probably as a result of the use ofDDT and otherpesticides. The population of USA and Canada has rebounded since and might even exceed historical numbers today, probably due to the combination of the ban on DDT and the proliferation of backyard bird feeders in North America which create unnaturally reliable and easy prey sources. Migratory sharp-shinned hawks are one of the most numerous raptors recorded at "hawk watches" across the country. An exception is thesubspecies fromPuerto Rico,Accipiter striatus venator, which is rare and listed asendangered by theU.S. Fish & Wildlife Service. The remaining resident subspecies from the Greater Antilles,fringilliodes from Cuba and nominate (A. s. striatus) from Hispaniola, are uncommon, local, and, at least in the case of the latter, decreasing. Bothventralis (plain-breasted hawk) anderythronemius (rufous-thighed hawk) are fairly common (but easily overlooked due to their secretive behavior) and presently considered safe. The situation forchionogaster (white-breasted hawk) is potentially more problematic due to its limited range, although it, at least locally, remains fairly common.
