The sharp-shinned hawk (Accipiter striatus) or northern sharp-shinned hawk, colloquially often nicknamed sharpie, is a small hawk, with males being the smallest hawks in the United States and Canada, but with the species averaging larger than some Neotropical species, such as the tiny hawk. The taxonomy is far from resolved, with some authorities considering the southern taxa to represent three separate species, white-breasted hawk (A. chionogaster), plain-breasted hawk (A. ventralis), and rufous-thighed hawk (A. erythronemius). The American Ornithological Society and some other checklists keep all four species conspecific. A recent genetic study additionally recommended splitting the three Caribbean island populations as three additional separate species, though this has not yet been adopted by any of the ornithological authorities.
Taxonomy The sharp-shinned hawk is sometimes separated into four species, with the northern group (see distribution) retaining both the scientific name and the common name sharp-shinned hawk (A. striatus). In addition to the nominate taxon A. s. striatus on Hispaniola, it includes the subspecies A. s. perobscurus on Haida Gwaii, A. s. velox in most of mainland North America, A. s. suttoni in northern Mexico and southern New Mexico, A. s. madrensis in southwest Mexico, A. s. fringilloides on Cuba, and A. s. venator on Puerto Rico. The three remaining taxa, each considered a monotypic species if split, are the white-breasted hawk (A. chionogaster Kaup, 1852 in southeast Mexico and Central America), plain-breasted hawk (A. ventralis Sclater, 1866 in the Andes) and rufous-thighed hawk (A. erythronemius Kaup, 1850 in southeastern South America). The breeding ranges of the groups are entirely allopatric, although the wintering range of the nominate group partially overlaps with the range of A. chionogaster (as is also the case with certain taxa within the nominate group). This allopatry combined with differences in plumage (see Appearance) and, apparently, certain measurements, has been the background for the split, but hard scientific data are presently lacking (AOU). Most material published in recent years (e.g. AOU, Ferguson-Lees et al. p. 586, and Dickinson et 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 approaching A. chionogaster. This has also been reflected in recent guides, where A. s. madrensis of southern Mexico is described as being relatively pale below (compared to more northern subspecies), but if this is a sign of intergradation with A. chionogaster or a north–south cline which includes both the members of the nominate group and A. chionogaster remains unclear. In Bolivia, A. ventralis and A. erythronemius approach each other, but no evidence of intergradation is known, something that, without actual specimens, would also be hard to prove due to the variability in the plumage of A. ventralis. A 2021 study of sharp-shinned hawks recommended recognising the three endemic Caribbean island subspecies as distinct species, based on analysis of their nuclear and mitochondrial DNA showing no modern contact between them, and diagnosed by their plumage; A. striatus, restricted to the island of Hispaniola, A. fringilloides to Cuba and A. venator to Puerto Rico. If this is accepted and A. striatus treated as endemic to Hispaniola, the continental complex then takes the scientific name A. velox.
Description
This is a small Accipiter 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 in Accipiter 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. Adults have short broad wings and a medium-length tail banded in blackish and gray with the tip varying among individuals from slightly notched through square to slightly rounded (often narrowly tipped white). The remiges (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 the cere is yellowish. The remaining plumage varies depending on group:
Nominate group: Cap dark and upperparts blue-grey (the former darker). Often, a few more-or-less random white spots can be seen on the scapulars (feathers attached to the wing that cover the meeting of wing and body). Underparts white with rufous or tawny bars. The crissum (the undertail coverts surrounding the cloaca) is white. Thighs rufous, but often barred white. The cheeks are tinged rufous (sometimes faint, but generally very distinct in taxa from the Greater Antilles). The irides are dark orange to red, but these are yellowish to pale orange in juveniles. Juveniles have dark brownish upperparts, each feather edged rufous, giving a rather scaly appearance. The brown head is streaked whitish, and the whitish underparts are extensively streaked brown or reddish and usually with reddish barring on the sides.
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