MORPHOMETRY AND SEXUAL DIMORPHISM IN THE YELLOW-LEGGED TINAMOU Crypturellus noctivagus noctivagus IN A RELICTUAL POPULATION FROM SOUTHERN BRAZIL

Abstract

The Yellow-legged Tinamou ( Crypturellus noctivagus ) is a terrestrial forest bird endemic to Brazil. Females and males of the subspecies Crypturellus noctivagus noctivagus are indistinguishable at the naked eye and there is lack of knowledge regarding means to discriminate sexes in the field. We investigated morphometric differences between sexes of C. n. noctivagus to determine which measures should be used to distinguish sexes. We compared eight morphometric measurements and total body mass of adult birds from a relictual population living in the wild, in the state of Rio Grande do Sul. Birds were captured during the breeding seasons of 2015 and 2016. Sex identification of individuals (four females and seven males) was obtained by molecular analysis. Differences between sexes were tested through Student’s t and Mann-Whitney’s tests and a through Principal Component Analysis. On average, females were 9.9% heavier and had bills 11.8% longer than males. Males had middle toes 8.7% larger and tails 19.0% larger than females, the latter presenting the highest degree of dimorphism among all measurements. Our results show that, when molecular sexing is not feasible, morphometric variables may be used to determine the sex of C. n. noctivagus individuals.