Iris Colour As an Indicator of Age Feature in Female Brazilian Tanagers (Passeriformes: Emberizidae) Confirmed by a Molecular Sexing Technique

Adults and particularly juveniles of many bird species are monomorphic, making determination of sex difficult. It is estimated that adult females appear identical to males in over 50% of the world's bird species (Griffiths et al. 1998). Besides that, the difference between males and females for some species is only recognisable in adults or subadults. In this case, until the difference in plumage becomes evident, the young are usually similar to adult females. Thus, morphological differences that can be used to easily identify the sex in birds are extremely important to facilitate many studies of behaviour, evolutionary ecology and evolution (Ellegren 1996). Ramphocelus bresilius, the Brazilian tanager, is an endemic species in Brazil, whose distribution extends from Paraiba state in the northeast to Santa Catarina in the southeast, thus encompassing almost the whole extent of the Atlantic forest. Adult R. bresilius exhibit a pronounced sexual dimorphism, with bright blood red plumage in the males, contrasting with black wings, tail and legs. A white callosity at the base of the jaw is emphasized by the dark bill. Adult females are greyish-brown on the back, with scattered reddish feathers dispersed on the rump and upper tail coverts. immature males and females have similar plumage to adult females and there is no apparent plumage difference between adult and young females (Sick 1997). Adult females and young males can only be distinguished after the first year, when young males start to acquire the first red feathers. The black and red plumage of the adult male is completed at the second year (Sick 1997).