Detailed description and seasonal variation in the diet of the Silvery-Cheeked Antshrike Sakesphorus cristatus (Wied, 1831) (Aves: Thamnophilidae) in a Brazilian semi-arid forest

Abstract

Despite being an important area for endemic species of birds, the Caatinga biome is highly fragmented due to anthropogenic influences and there is a lack of study on many aspects of its birds’ biology. In this semiarid environment, rainfall is highly seasonal, with two different and well-defined periods: a long dry season, and a short rainy season. This study aimed to qualify and quantify the diet of Sakesphorus cristatus, an endemic thamnophilid bird of the Caatinga, as well as to determine whether there was temporal variation between two different seasons and between dry seasons of two consecutive years. Surprisingly, this was the first study to have focused on describing and quantifying items found of any bird species’ diet in the Caatinga. We analyzed the stomach contents of 72 specimens collected in the municipality of São Felix do Coribe, Bahia, Brazil. Data analysis included relative abundance and occurrence, average consumption/sample and alimentary importance index of each food category. Sampling adequacy was assessed using cumulative curves constructed with diversity index and coefficient of variation. In general there is a high predominance of ants and termites, with seasonal shifts in the proportion of each item, and a high contribution of caterpillars during the breeding season. During the dry season, the most predominant prey categories in the diet were Formicidae, Isoptera and Coleoptera (adult, A), while during the rainy season, there was an increase in the proportion of Isoptera, Coleoptera (A) and Lepidoptera (larvae) consumption and a decrease in Formicidae. There was no significant difference between consumption of prey items between the two dry seasons. The overall analysis suggests that S. cristatus feeds mainly on the aforementioned insects and is an opportunistic species, adjusting its diet according to their prey availability.