Mixed-Sex Phenotypes in the Andean Condor: Naturally Occurring Abnormality or Environmentally Induced Disorder? Available to Purchase

Sexual dimorphism, i.e., the phenotypic differences between males and females of the same species, is quite common among birds but the only vulture with clearly defined sexual differences is the Andean Condor (Vultur gryphus). There are several sex-specific phenotypic differences between adult males and females in this species, but three important differences are (1) body mass, in which males are up to twice the weight of females, (2) the presence of a comb, which crowns the head of males but is absent in females, and (3) the color of the iris, which is light brown in males and scarlet red in females (Fig. 1A, B). Curiously, in Andean Patagonia in autumn 2018 we observed an individual condor displaying a mixed-sex phenotype (Fig. 1C), somewhat similar to the phenomenon we had previously observed in three condors we trapped for other research on a sheep...