Thursday, February 27, 2014

Dark Morph Rough-legged Hawk in Canon City


I spotted this hawk on the bluff not far from my house as I drove by then turned around to check it out. I originally thought it was a Harlan's Red-tailed Hawk. However, on closer examination of my photos I could see the following field marks consistent with an dark morph Rough-legged Hawk described by Brian Wheeler in Raptors of Western North America (p.390): "Very defined white mask. Yellow gape is narrow but obvious as it contrasts against the dark head." The yellow gape is clearer when the photos are enlarged further (tho parts get more blurry).

I believe this bird fits best the 'Adult brown type' described by Wheeler as one of 3 subtypes whose head is "all dark without pale supercilium and auricular regions." (p. 390). In describing the body of this type, Wheeler states,"There is often a sharp demarcation line between the more tawny-brown neck and breast and the darker, uniformly blackish brown belly and flanks." (p.391)

This bird appears to have the tail type described by Wheeler as "Partially banded type (many females, some males)--Ventral surface is pale gray with partial, narrow gray bands." (p. 391) Dark morphs are usually noted to be less than 10% of the Rough-legged Hawks in western U.S. which follows Gloger’s Rule: ("the amount of black pigment increases with more humidity") SeEtta