Breeding ecology of the Bare-Faced Ibis (Phimosus infuscatus) in Southern Brazil

Abstract

The Bare-faced Ibis is a gregarious bird found in South America. In the face of a rapid expansion in a southern state in Brazil and a lack of detailed information about the species' reproduction, two breeding areas were studied weekly for two consecutive seasons. We registered numbers and characteristics of adults, nests, eggs, and chicks, calculated success estimates, and assessed nest installation preferences. Chick morphology, age, and measurements served to define five growth stages. The species used the margins of two close rivers in Santa Catarina to build nests, lay eggs, and develop parental care between August and January, with success estimates as expected for the family. We observed a preference for the eastern margin of the rivers and proximity to bridges for nest installation, where the muddy margin provides resources for juvenile feeding. Two colony models were defined based on the near or far installation of the nests. Variations in egg and chick dimensions indicated higher adult investment in the second season, with negative allometric growth of the bill and tarsus of chicks related to weight. The results presented suggest favorable conditions for the species’ reproduction in the region, a considerable factor in understanding its expansion in recent years.