The Alaska Red-tailed Hawk

William S. Clark
2018 Western Birds  
Grinnell (1909:211) described a new subspecies of the Red-tailed Hawk, Buteo jamaicensis alascensis, as "always blackest dorsally, and decidedly smaller" than a "large series" of Western Red-tailed Hawks, B. j. calurus, at that time the only subspecies of B. jamaicensis recognized in western North America. He based his description of this "Alaska Red-tailed Hawk" on four specimens collected in 1907 in southeast Alaska (Figures 1-3 ), two of which he designated as the type specimens. Grinnell
more » ... pared the adult type, MVZ 51 (♂), with adults of calurus and found it darker dorsally, with a wider dark subterminal tail band, stronger flank barring, and wider black shaft streaks on the belly. The other three specimens comprise a juvenile (MVZ 41), also designated as a type, and both of its parents. The latter (MVZ 42, ♀; MVZ 43, ♂) are more typical of alascensis in having the breast rufous (Figures 2 and 3 ). Grinnell wrote that the juvenile type specimen is also darker above and has the dark tail bands wider than those of juvenile calurus; he saw no suggestion of a dark morph in alascensis. So far as known, the range of alascensis comprises the temperate rain forests of southeast Alaska and coastal British Columbia, including the Queen Charlotte Islands (now Haida Gwaii) and western Vancouver Island (see Hellmayr and Conover 1949, Wheeler 2003). The Western Red-tailed Hawk breeds east of this subspecies' range in British Columbia (Clark and Wheeler 2001), and Harlan's Hawk (B. j. harlani) breeds north of its range, in most of the rest of Alaska, the Yukon, and northwestern British Columbia. Clark and Wheeler (2001) and Liguori and Sullivan (2010) described and depicted the many differences between harlani and the other subspecies of the Red-tailed Hawk. Field guides to North American birds in general (e.g., Sibley 2000, Dunn and Alderfer 2011) do not describe or depict B. j. alascensis. Clark and Wheeler (2001) and Wheeler (2003) described adult and juvenile plumages of this subspecies in their species accounts, but did not depict them. Other raptor guides (e.g., Wheeler and Clark 2003 , Liguori 2005 , 2011 , Dunne et al. 2012 , Crossley et al. 2013) have not described or depicted this subspecies. I examined 45 specimens of this little-known taxon, including the type specimens, in 10 museums. Gus van Vliet, Chuck Susie, Amy Clark Courtney, and Elleana Elliot sent me more than 20 photos of Red-tailed Hawks taken in southeast Alaska over the last decade. When I replied to van Vliet that they were typical alascensis, he said that he did not know precisely what that was and suggested that I write an article on the field identification of this subspecies so that Red-tailed Hawks in southeast Alaska could be properly evaluated. Twenty-five of 27 adult alascensis specimens examined, including the adult type (Figures 1-3 ), have a decided rufous wash on the breast but not much rufous on the belly (Figure 4 ). In this they differ from the rufous morph of adult calurus, which has a mostly rufous belly (Clark and Wheeler 2001: plate 25, figures 1a and 1f). Interestingly, the adult type specimen lacks this rufous wash (Figure 1 ). Two of these 27 adult specimens also have some whitish on the breast (perhaps due to interbreeding with harlani). All show much less tawny on the scapulars than does adult calurus (Figures 2-4 ), most have numerous dark tail bands, and all have a rather wide dark subterminal band (Figure 4 ) and a rufous breast. Figures 5-7 show adults from southeast Alaska, and Figures 8 and 9 show adults being rehabilitated in (and probably also from) southeast Alaska.
doi:10.21199/wb49.2.3 fatcat:vfiac2tz3vaxlorj2xkepizaee