An approach to sexing young Great Bustards Otis tarda using discriminant analysis and molecular techniques

Adult Great Bustards Otis tarda are sexually dimorphic, males weighing more than twice as much as females. However, there is no practical way to distinguish sex in chicks by their morphology. In this paper we describe a discriminant function, Tail Length/Weight, which correctly sexed 98.2% of 165 Great Bustard chicks at two study areas in Spain, the Wildlife Reserve of Lagunas de Villafáfila and the province of Madrid. The value for Tail Length/Weight separating the sexes was 0.099: Tail Length/Weight for males < 0.099 < Tail Length/Weight for females. We also show that the recently described PCR-based sex determination technique using genomic DNA is valid for the Great Bustard. Both approaches should be useful for sexing young Great Bustards in captive breeding programmes and studies on wild populations.