Eastern red-tailed hawk

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Eastern red-tailed hawk
Buteo jamaicensis borealis 60339473.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Accipitriformes
Family: Accipitridae
Genus: Buteo
Species:
Subspecies:
B. j. borealis
Trinomial name
Buteo jamaicensis borealis
(Gmelin, 1788)

The eastern red-tailed hawk (Buteo jamaicensis borealis) [1] is a subspecies of the red-tailed hawk that breeds from southeast Canada and Maine south through Texas and east to northern Florida.

Contents

Range

The race breeds below the Arctic (unlike more western birds which can reach the sub-Arctic as breeders), and is absent from all but the southernmost part of the Hudson Bay and roughly the northern third of both Quebec and Newfoundland. [2] Wintering migrants from southern Ontario may range east to southern Maine and south to as far as the Gulf Coast and Florida. [3] The western limits of this race's range are slightly ambiguous and they may hybridize extensively with the western red-tailed hawk (Buteo jamaicensis calurus) in timbered stretches of the Great Plains. The breeding range of B. j. borealis seems to include most of Texas (perhaps excluding the western sections), Oklahoma, Kansas and Nebraska. In the Dakotas and even eastern Wyoming, some B. j. borealis may occur but give way mostly to B. j. calurus and/or Krider's hawk (B. j. kriderii), with the B. j. borealis type hawks breeding without race mixing to the western border of Minnesota and the eastern third of Manitoba. [4] [2]

Description

This is a large-bodied, relatively heavy race, but differs from more westerly hawks in having a relatively smaller wing area. Based on linear dimensions, this subspecies shows the most size variation and, unlike the red-tailed hawk species overall, size variation seems to fall within Bergmann's rule as northern birds average larger than southern ones. [5] [6] [7] [8] The wing chord of males can range from 337 to 396 mm (13.3 to 15.6 in), averaging 370.1 mm (14.57 in), and, in females, it ranges from 370 to 427 mm (14.6 to 16.8 in), averaging 390.2 mm (15.36 in). Additionally, males and females average 215.4 and 230.1 mm (8.48 and 9.06 in) in tail length, 82.4 and 85 mm (3.24 and 3.35 in) in tarsal length and 25.1 and 27.6 mm (0.99 and 1.09 in) in culmen length. [5] [6] [4] [7] [9] The largest known sample of body weights from unambiguous B. j. borealis was from Wisconsin migrants, with 34 males averaging 945.3 g (2.084 lb) and 24 females averaging 1,222.4 g (2.695 lb). [6] This race only has pale morphs and almost always bears a whitish ground color with little barring overall, including a variably present dark necklace, a frequently absent or much reduced belly band and little to no barring on the flanks or the upper legs. Immature B. j. borealis tend to have dark spotting on leg feathers but otherwise average paler than immatures of most other races. [5] [6] This race includes a form from the northern stretches of its range (mostly breeding within Canada), formerly considered as B. j. abieticola. Birds of B. j. abieticola type are more heavily marked below than typical B. j. borealis and, thus B. j. borealis seem to correspond to Gloger's rule, as well. This plumage variation appears to be a regional adaptation to the denser boreal forest. [10] [11]

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The Socorro red-tailed hawk is a subspecies of red-tailed hawk endemic to Socorro Island, 600 kilometres (370 mi) off the west coast of Mexico. The wing chord of males can range from 368 to 385 mm, averaging 378.4 mm (14.90 in), and, in females, it ranges from 385 to 415 mm, averaging 412.8 mm (16.25 in). Males and females average 214.1 and 230.4 mm in tail length, 84.9 and 89.1 mm in tarsal length and 24.9 and 28.6 mm in culmen length. One female was found to have weighed 1,260 g (2.78 lb). This race, which is physically fairly similar to the western red-tailed hawk, is not recognized by some authorities because it has a breeding population of perhaps fewer than 20 birds. There are some differences from B. j. calurus, such as their larger, more robust feet and much greater sexual dimorphism, which is the most pronounced of any race linearly, averaging 10.42% when all standard measurements are considered. Furthermore, Socorro hawks tend to average more melantic in overall color, being a duller, darker brown than mainland birds.

<span class="mw-page-title-main">Cuban red-tailed hawk</span> Subspecies of bird

The Cuban red-tailed hawk is a subspecies of red-tailed hawk native to the Bahamas, Florida, and Cuba.

<span class="mw-page-title-main">Florida red-tailed hawk</span> Subspecies of bird

The Florida red-tailed hawk is a subspecies of red-tailed hawk. It occurs year-round in peninsular Florida north as far as Tampa Bay and the Kissimmee Prairie and south down to the Florida Keys. This subspecies is very large, only the southwestern red-tailed hawk averages larger in overall dimensions. Although a non-migratory subspecies, its wings are notably longer than those of the eastern red-tailed hawk and S. b. umbrinus may be conspicuously larger than the relatively small southern S. b. borealis that they overlap with. The wing chord of males can range from 396 to 400 mm, averaging 398.8 mm (15.70 in), and, in females, it ranges from 373 to 432 mm, averaging 408.9 mm (16.10 in). Males and females average 225 and 234 mm in tail length, 91.1 and 88.9 mm in tarsal length and 27.2 and 30 mm in culmen length. Compared to B. j. borealis which it replaces, it has a darker back, more similar to the dark brown of the western red-tailed hawk. Adults tend to have chestnut to rufous side patches, multiple tail bars and no barring on the "trousers". A very rare dark morph has been reported.

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 2014-05-04. 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. 1 2 Johnsgard, P. A. (1990). Hawks, Eagles, & Falcons of North America: Biology and Natural History. Smithsonian Institution.
  3. Tesky, Julie L. "Buteo jamaicensis". United States Department of Agriculture . Retrieved 10 June 2007.
  4. 1 2 Preston, C. R. & Beane, R. D. (2009). "Red-tailed Hawk (Buteo jamaicensis)". The Birds of North America. doi : 10.2173/bna.52.
  5. 1 2 3 Ferguson-Lees, J.; Christie, D. (2001). Raptors of the World. London: Christopher Helm. ISBN   978-0-7136-8026-3.
  6. 1 2 3 4 Palmer, R. S., ed. (1988). Handbook of North American birds. Volume 5 Diurnal Raptors (part 2).
  7. 1 2 Pearlstine, E. V., & Thompson, D. B. (2004). "Geographic variation in morphology of four species of migratory raptors". Journal of Raptor Research. 38: 334–342.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  8. Fitzpatrick, B. M. & Dunk, J. R. (1999). "Ecogeographic variation in morphology of Red-tailed Hawks in western North America". Journal of Raptor Research. 33 (4): 305–312.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  9. 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.
  10. Dickerman, R. W., & Parkes, C. (1987). Subspecies of the Red-tailed Hawk in the Northeast. Federation of New York State Birds Clubs, Inc.
  11. Wheeler, B. K. (2003). Raptors of Western North America. Princeton University Press.