How birds age? Chilean Elaenia as an example for the Neotropical bird species

Determining the age of birds is important to understand the demographic dynamic, since the effects of mortality factors may depend on the age of the individuals. Several methods have been used to determine the age of many European and North American bird species, but little is known about aging in Neotropical birds. The aim of our research was to evaluate the method for aging Chilean Elaenia ( Elaenia chilensis ) through individuals of known age. We used the palate color and feather molt limits of individuals of known age, together with the previously available proposals for aging this species to propose a new criterion for determining the age of Chilean Elaenias. Our criterion makes possible to differentiate adult individuals in the first, second, and third year since their born. We consider that our proposal will allow to advance towards more detailed research on the population dynamics of bird species in South America.