Harlan's hawk

Harlan's hawk or Harlan's red-tailed hawk (Buteo jamaicensis harlani)[1] is a subspecies of the red-tailed hawk.

Harlan's hawk
A Harlan's hawk illustrates its silvery-white tail.
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Accipitriformes
Family: Accipitridae
Genus: Buteo
Species:
B. jamaicensis
Subspecies:
B. j. harlani
Trinomial name
Buteo jamaicensis harlani
(Audubon, 1830)

Description

While similar in linear dimensions to the western red-tailed hawk (B. j. calurus), this race is sometimes described as slighter and lighter.[2] On the contrary, though, they are highly sexually dimorphic in size (the most dimorphic of any in the United States) and mature females are sometimes more massive than almost any female B. j. calurus.[3] However, B. j. calurus tends to have a much longer tarsus than Harlan's hawks do, as expected due to the latter's habitation to cold environments almost year around.[4] The wing chord of males can range from 365 to 390 mm (14.4 to 15.4 in), averaging 381 mm (15.0 in), and, in females, it ranges from 390 to 430 mm (15 to 17 in), averaging 408.7 mm (16.09 in). Males and females average 211 and 225.3 mm (8.31 and 8.87 in) in tail length, 79.8 and 87 mm (3.14 and 3.43 in) in tarsal length and 24.7 and 27 mm (0.97 and 1.06 in) in culmen length.[5][6][7] A wintering female in eastern Kansas weighed 1,629 g (3.591 lb).[8] The historic taxonomic status of Harlan's hawk has been quite erratic, sometimes it has been classified as its own species, B. harlani to the opposite extreme that R. S. Palmer (1988) classified as it (perhaps improbably) as a mere western color morph. Most modern authorities recognize as a valid subspecies.[3][4][9] Harlan's hawk is markedly different from all other red tails and can be identified nearly 100% of the time by an experienced hawk watcher.[4][9] Throughout the morphs of this subspecies, the plumage is predominantly blackish, lacking any warmer or brownish tones (save the tail). Harlan's hawks usually have faint streaks on the sides of their head and about their chest with a little gray mottling or speckling on the scapulars. Apart from a variably white-streaked throat, their underparts are usually mostly black with variable white streaking and barring on the thighs or crissum. There are up to four main variations from the typical one above: extreme dark morph (where even the throat is black and no pale streaking is present), dark morph (with barring still present from the tarsus to the underside), rare pale morph (with few blackish blobs on the belly and generally a whiter head) and perhaps even rarer types where the base color is grayish. Unlike most red-tailed hawks, generally immatures are similar enough than adults that it can be difficult to distinguish them. On average, immatures have more extensive pale streaking above and mottling below, but much individual variation has been recorded. The typical tail of a Harlan's hawk is white with a thick black subterminal band but individuals may vary considerable and the tail may be reddish, dusky, whitish or gray and can be longitudinally streaked, mottled or barred.[5][4][9]

Distribution

It breeds from central Alaska to northwestern Canada, with the largest number of birds breeding in the Yukon or western Alaska, reaching their southern limit in north-central British Columbia. The Harlan's hawk is restricted as a breeder to pure taiga habitat. Harlan's hawk winters from Nebraska and Kansas to Texas and northern Louisiana, with a rare bird found as far east as Tennessee.[6][10][11][12]

References
  1. Sibley, David Allen (19 December 2009). "Subspecies names in the Sibley Guide to Birds". Sibley Guides: Identification of North American Birds and Trees. Random House. Archived from the original on 4 May 2014. Retrieved 4 May 2014. Website based on / supplement to book, Sibley, David Allen (11 March 2014). The Sibley Guide to Birds (Second ed.). Knopf Doubleday (Random House). ISBN 9780307957900.
  2. Dunne, P.; Sibley, D. & Sutton, C. (1988). Hawks in Flight: The Flight Identification of North American Migrant Raptors. Houghton Mifflin Harcourt.
  3. Palmer, R. S. ed. (1988). Handbook of North American Birds. Volume 5 Diurnal Raptors (Part 2).
  4. Clark, W. S. (2014). "Harlan's Hawk differs from Red-Tailed Hawk". Global Raptor Information Network.
  5. Ferguson-Lees, J. & Christie, D. (2001). Raptors of the World. London: Christopher Helm. ISBN 978-0-7136-8026-3.
  6. Preston, C. R. & Beane, R. D. (2009). "Red-tailed Hawk (Buteo jamaicensis)". The Birds of North America. doi:10.2173/bna.52.
  7. Ridgway, R. & Friedmann, H. (1919). The Birds of North and Middle America: A Descriptive Catalogue of the Higher Groups, Genera, Species, and Subspecies of Birds Known to Occur in North America, from the Arctic Lands to the Isthmus of Panama, the West Indies and Other Islands of the Caribbean Sea, and the Galapagos Archipelago. Vol. 50, No. 8. Govt. Print.
  8. Imler, R. H. (1937). "Weights of some birds of prey of western Kansas" (PDF). Bird-banding. 8 (4): 166–169. doi:10.2307/4509472. JSTOR 4509472.
  9. Liguori, J. & Sullivan, B. L. (2010). "Comparison of Harlan's hawk with Eastern & Western Red-tailed Hawks". Birding: 30–37.CS1 maint: multiple names: authors list (link)
  10. Tesky, Julie L. "Buteo jamaicensis". United States Department of Agriculture. Retrieved 10 June 2007.
  11. Johnsgard, P. A. (1990). Hawks, Eagles, & Falcons of North America: Biology and Natural History. Smithsonian Institution.
  12. Taverner, P. A. (1927). "A study of Buteo borealis, the Red-tailed Hawk, and its varieties in Canada (No. 13)". Canada. Victoria Memorial Museum.
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