A Quantitative Study of Nasal Bristle Length in the Common and Chihuahuan Ravens

Abstract

the proportionately longer nasal bristles of the Chihuahuan raven (Corvus cryptoleucus) have been adduced as a character distinguishing that species from the Common raven (C. corax). in a sample of 113 specimens of the Common raven and 86 of the Chihuahuan we confirmed that the average of the bristle-to-bill ratio differs significantly in the two species, being 26% greater in the Chihuahuan. But the overlap is wide: only 36% of the Chihuahuan ravens and 22% of the Common ravens fell outside the zone of overlap. on the basis of this character, only ravens with a ratio <0.45 can be identified as the Common, while those with a ratio >0.60 are almost all Chihuahuan.