Predação de ninhos de Formicivora littoralis e Thamnophilus ambiguus (Aves: Thamnophilidae) na Restinga de Massambaba, RJ: influência do micro-hábitat na taxa de predação

Abstract

Nest predation is the major cause of reproductive failure of birds and strategies to reduce this risk are favored by natural selection. Several factors influence the nest predationrate, including nest site. The identification of key characteristics of the nests sites chosen is important to understand the evolutionary strategies of birds. Formicivora littoralis and Thamnophilus ambiguus are two endemic Thamnophilidae of the Atlantic Forest biome that co-occur in Restinga environment, the first being endangered and restricted to this environment. The habitat fragmentation, as well as the invasion of P. penicillata and C. penicillata in the Restinga environment are factors that can enhance birdnests predation. This study, conducted in Restinga of Massambaba (Araruama, RJ), aimed to understand the biology of nest predation related to thesebirds of the Restinga. Chapter 1 aims to identify nest predators of F. littoralis and T. ambiguus and investigate the occurrence of Callithrix spp. in the study area. Chapter 2 aimed to understand the influences of F. littoralis nesting micro-habitat in the nest predation rate. To identify predators, active nests of the model species were mapped and 30 artificial nests distributed in the study area. The monitoring of the nests was made with camera traps. Callithrix spp. Censuses were conducted (C. jacchus, C. penicillata and hybrid). For the F. littoralis nesting micro-habitat characterization we placed two Belgian canary eggs in inactive nests. Quantifiedmicro-habitat variables were:structure, density, vegetation type, nest height, distance to the nearest track, support plant height and percentage of nest cover. The daily survival rate (DSR) and the relationship between the DSRand the variables of microhabitat were analyzed in the Mark program. The nest predation rate of F. littoralis and T. ambiguus were, respectively, 100% and 75%. DSR, respectively, 86% and 80%. The main predator recorded for both species was Callithrix spp. It was also registered the following predators in natural nests: Didelphidae, Guira Guira, Rupornis magnirostris. Thamnophilus ambiguus and Penelope superciliaris were recorded in experimental nests. The experimental nests obtained predation rate and DSR respectively of 87.5% and 97.7%. The nest cover and physiognomy influenced the survival rate of experimental nests. Predation was the main cause of failure, as expected. The records of predators of F. littoralis and T. ambiguus nests were, with the exception of G. Guira, unpublished. The high incidence of predation by Callithrix spp. indicates the negative impact caused by these mammals in the Restinga ecosystem, indicating an urgent need for management measures in the study area