Selective predation by the White-browed Warbler (Myiothlypis leucoblephara), a Neotropical understorey insectivorous bird

Abstract

ABSTRACT The diet composition and feeding preference of Myiothlypis leucoblephara (White-browed Warbler, Parulidae) were investigated in an area of the Atlantic Forest, Brazil, based on fecal samples and availability of field arthropods. Hymenoptera Formicidae and Coleoptera were the predominant taxa in the diet, corresponding to more than 70% of all items. Myiothlypis leucoblephara exhibited a preference for prey types, mainly Formicidae and Coleoptera (λ = 0.123, p = 0.01), which are the proportionally more consumed taxa when compared to other types of prey. The species also showed preference for prey sizes, with arthropods of the size classes between 2 mm-6 mm being proportionally more consumed (λ = 0.214, p = 0.001). Although it forages predominantly on the ground, M. leucoblephara also preys on arthropods regularly on the foliage, which allows expanding the range of substrates exploited as well as obtaining different types of prey, probably favoring the differential consumption. On the other hand, the preference for intermediate size prey suggests foraging optimization, consuming feeding items with high energy-intake rate in relation to costs of predation. Whether the preference results from active selection by the birds or simply by the difficulty of finding less abundant items needs to be investigated.