Nest predation and its importance for a neotropical bird, the western slaty antshrike (Thamnophilus atrinucha): The problem, experiments and simulations

Nest predation is a major cause of reproduction failure for many species of passerine birds. Thus, nest predation has received much attention regarding its influence on the evolution of avian life histories and nest-site and habitat selection. Differences between tropical and temperate birds in these life history and nest-site traits have often been attributed to nest predation, since nest predation is higher in the tropics. However, the lack of data for tropical birds has limited adequate examination of these questions. Here I describe the breeding cycle and nesting success of a typical neotropical passerine bird. With that background, I experimentally examine aspects of nest-site and habitat selection and their influence on nest predation and nesting success. Finally a simulation study is used to examine the influence that nest predation may have on reproductive success of tropical and temperate birds, given their different regimes of breeding season length, renesting intervals, and predation rates. Nest predation rates are very high in antshrikes and several other bird species that nest similarly. Nest-sites do not vary widely in predation risk, nor do vegetation components of the nest area exert strong influences on predation. Predation rates, and nest site influences on predation, differ on natural and experimental nests. These differences are due to the different predators that prey upon natural and experimental nests. Simulations show that variation in nest predation rates influences fitness more when nest predation rates are low, and number of nesting attempts influences fitness most at high predation rates