We compared the plumage, morphology, and the alarm call of two taxa of the Gray Hawk (Buteo nitidus) from north and south of a distributional gap in the species' range in Costa Rica. We found all age and sex classes completely distinguishable on the basis of several discrete plumage features. Three of four age and sex classes were diagnosably distinct by measurements of external morphology alone, and the two taxa had diagnosably different alarm calls. On the basis of the level and stability of morphological differentiation, and consistent with prior work suggesting substantial genetic differentiation between the two taxa, we recommend they be recognized as full species, B. nitidus, the Gray-lined Hawk, south of the distributional gap in Costa Rica, and B. plagiatus, the Gray Hawk, north of the gap.
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1 May 2011
The Gray Hawk (Buteo nitidus) is Two Species
Brian A. Millsap,
Sergio H. Seipke,
William S. Clark
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The Condor
Vol. 113 • No. 2
May 2011
Vol. 113 • No. 2
May 2011
Buteo nitidus
Buteo plagiatus
Gray Hawk
Gray-lined Hawk
species
taxonomy