Breeding biology of Pale-breasted Thrush Turdus leucomelas (Turdidae) in the north of Atlantic Forest, Brazil

Abstract

Reproduction is a key process in the life of organisms and represents high-energy cost to the parents, and often a tradeoff between survival and reproductive success. The breeding biology is an important aspect to be studied, which has inspired theories about bird life history evolution, such as the latitudinal gradient in the clutch size related to different survival rates between the temperate and tropical regions. To contribute with the knowledge of breeding ecology of tropical birds we monitored two reproductive periods of the Pale-breasted Thrush Turdus leucomelas in the northeastern Brazil. The breeding period in the studied area occurred from December through April. We found the nests mainly on Facheiro cactus (Cactaceae) at 1.43 ± 0.35 m above the ground. They were composed by roots, mosses, fungus mycelium, leaves, twigs, and a mix of fragmented vegetal material with soil and sand at the base. We found clutch sizes of three (n = 9), two (n = 3) and one (n = 1) eggs. The eggs (n = 21) had mass of 5.1 ± 0.9 g and measured 26.6 ± 1.3 mm by 19.5 ± 0.5 mm. We observed 12 days of incubation and 14 days of nestling period. The Mayfield nest success in 2013 was 7.3% and in 2014 it was 4.5%, lower during the nestling period than during the incubation in both years. Our results show that T. leucomelas breeds in the area in the beginning of rainy season, when the frequency of occurrence of the migrant Turdus amaurochalinus is low. In addition, the low nest success observed may be a consequence of the localization of the studied area in the periphery of the species range, where limited resources probably result in reduced fitness.