Juv. Gray Hawk vs. Juv. Gray-lined Hawk
- In the most recent 53rd Supplement the AOU split the Gray Hawk (Buteo
nitidus) into two species, northern Gray Hawk (Buteo plagiatus) and
southern Gray-lined Hawk (Buteo nitidus). In this decision they cited a
publication by Milsap et al. (2011).
According to BNA these two species differ in juvenal plumage as follows.
GRAY HAWK - "Juvenile has dark crown, dorsal webs of outer primaries white
due to light barring, 5–9 dark bars on tail, barring on thighs, markings on
underparts sparser and smaller (more streaklike)"
GRAY-LINED HAWK - "Juvenile has light crown with few dark streaks, dorsal
webs of outer primaries orangish-buff, 0–6 dark bars on tail, streaked or
immaculate thighs, and heavier spotlike markings on underparts."
Currently a bird identified as a juvenile GRAY HAWK is being seen in Santa
Barbara, California and is widely regarded as the first fully documented
bird for the state, although whether the Gray-lined Hawk is fully
eliminated as been raised.
Here is a selection of photos of the Santa Barbara bird:
Based on the photos and the BNA descriptions, the bird seems to best fit
Gray Hawk in that it appears to have a dark crown, at least 9 dark tail
bars, and some barring on thighs.
The paper by Milsap et. al contains a useful color plate (see PDF below)
showing some additional differences between these two species. Juv.
Gray-lined has large dark blotches on the underparts, more less white on
the uppertail coverts and has a pale window on the upperside of the
primaries while Gray lacks large dark ventral blotches, has more white on
the uppertail coverts and lacks pale windows on the primaries.
The Auk 129(3):573-588, 2012
Bibles, Brent D., Richard L. Glinski and R. Roy Johnson. 2002. Gray Hawk
(Asturina nitida), The Birds of North America Online (A. Poole, Ed.).
Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North
America Online: http://bna.birds.cornell.edu/bna/species/652
Millsap, B. A., S. H. Seipke, and W. S. Clark. 2011. The Gray
Hawk (Buteo nitidus) is two species. Condor 113:326–339.
Joseph Morlan, Pacifica, CA
"It turns out we're very good at not seeing things" - Jack Hitt