Dieta e comportamento de forrageio de Thamnophilus pelzelni (Hellmayr, 1924) (Aves: Thamnophilidae) em relação à disponibilidade de presas em uma área de Floresta Estacional Decidual

Abstract

In seasonal environments, such as seasonal deciduous forest, there is a marked variation in the arthropod community between wet and dry seasons. Therefore, insectivorous birds that live in these forests, such as Thamnophilus pelzelni, should exhibit varies in their foraging strategy to ensure that their energy demands are met under different resource availabilities. The objective of this work was to test the hypothesis that the diet and behaviour of T. pelzelni change in response to the abundance of prey in the environment. Collections were made in the Parque Estadual da Mata Seca, na area of Seasonal Deciduous Forest, in february, may and september. For each month of collecting, ten sampling points were marked where arthropods were collected by using pitfall traps, composite interseption traps and through beating. Simultaneous to the arthropod collection, and at the same sampling points, the diet of individual birds was sampled by forced regurgitation. In addition, foraging behaviour in this species was studied through focal observations. The results show that there was no relation between the richness of items ingested by T. pelzelni and the abundance of prey in the environment, while the abundance of prey consumed by this species increased with the reduction of resource abundance. The composition of the diet of T. pelzelni was similar in february and may and only differed in september. In february and may the most abundant prey in the diet of T. pelzelni were Orthoptera, Arthropoda pupa and eggs and Coleoptera, while in september there was a significant increase in the amount of Isoptera and Formicidae consumed. The individuals of T. pelzelni foraged as much in the soil as in the forest understory, capturing prey in the leaf litter, leaves, trunks, branches and in the air during flight. The manoeuvres used by this species to capture prey were classified as: picking up, flying, stretching, jumping, and stretching the body with the head facing down. There was a difference in the frequency that different substrates and manoeuvres were used during the collecting months. It was possible to observe, through diet and foraging behaviour, the response of T. pelzelni to the availability of resources in the environment