VARIATION IN FORAGING STRATEGY WITH FOREST AGE FOR THE BLACK-CROWNED ANTSHRIKE (THAMNOPHILUS ATRINUCHA)

Abstract

Rapid deforestation leads to loss and degradation of avian habitat. Reforestation and natural regeneration create secondary forests that may play an important role in maintaining avian biodiversity. In the tropics, many understory insectivores are absent from secondary forests; however the mechanisms responsible for this pattern are unknown. Differences in foraging behavior can be used to identify changes to the insect community, which may contribute to this pattern. We investigated foraging behavior in a common understory insectivore, the Black-crowned Antshrike (Thamnophilus atrinucha), across three forest-age groups to test the hypothesis that insect (prey) communities differ with forest age. We observed no difference in attack or foraging success rates by Black-crowned Antshrikes, suggesting equal foraging effort during focal observations. However, individuals consumed less high-quality (large) prey in secondary forest. Additionally, foraging range shifted downwards from 8.5 ± 1.3 m to 4.5 ± 0.6 m and was compressed horizontally in secondary forests, reducing inter-vegetation movement during foraging bouts. We suggest that this provides indirect support for a change in the insect community across forest ages. Black-crowned Antshrikes appear flexible in their foraging strategies; an ability that may not be shared by other species. However, reduced biomass consumption coupled with constant attack/success rates suggest individuals are performing poorly in young forest. Further research should investigate the generality of this pattern and the capacity for flexible foraging strategies in other avian species.