Gender identification in the Swainson's Hawk Buteo swainsoni using molecular procedures and discriminant function analysis

SARASOLA, J.H.; NEGRO, J.J.

JOURNAL OF RAPTOR RESEARCH

Año: 2004 vol. 38 p. 357 - 361

0892-1016

The Swainson´s Hawks Buteo swainsoni is a slightly dimorphic bird of prey, and although females are usually larger than males, sexing may be difficult even when birds are captured and handled. In this paper, we present a method for gender determination of Swainson´s Hawks based in molecular sexing and discriminant analysis. The method is based on samples and morphometric measurements from one hundred and four free-living Swainson´s Hawks captured in their wintering ranges during the austral summers 2002-03 and 2003-04. We found significant differences between the sexes for all morphometric measures considered, while juveniles and adults only differed in body mass, culmen and hallux length. Using only forearm length as a predictor variable, our discriminant function method approached 89.4% and 93.9% accuracy in correctly sexing male and female individuals. A second function considering forearm, tail length and wing chord improved separation of groups as well as the total percentage of individuals correctly discriminated by sex (97.0% and 93.3% for male and female). The use of body measures related to structural size such as the forearm, make this method reliable and of wide applicability, even for birds belonging to different age classes.