Seasonality drives variation in the use of forest strata by adult males of a dimorphic frugivorous bird species

Abstract

AbstractAnimals may exploit habitat complexity in a myriad of ways, and a widespread pattern of habitat use is vertical stratification. In tropical forests, it often increases niche diversity for frugivorous birds, and it strongly influences seed dispersal and community persistence. Yet, most studies disregard intraspecific variations in the use of forest layers and their ecological and evolutionary consequences. In this study, we asked whether adult males and green individuals (females and juveniles) of a dimorphic frugivorous bird, the helmeted manakin (Antilophia galeata, Pipridae) foraged at different strata in a forest from Southeastern Brazil. We also investigated how the seasonal dynamics of fruit availability and distribution within the forest affect between‐ and within‐phenotype use of forest layers. We conducted field observations of the foraging activity of both phenotypes and found that they were mainly midstory foragers flying at similar heights in both seasons. However, adult males increased their stratum breadth and their foraging height during the wet season, when fruits were also available at higher strata, while the foraging behaviour of green individuals remained seasonally invariant. The different effects of seasonality on the phenotypes of the helmeted manakin may be a consequence of sexual competition among adult males in the wet season to secure fruits in taller plants. Altogether, our findings show that seasonality affects differently the spatial use behaviours of males and green individuals, and understanding these intraspecific differences may help us predict how species respond to environmental disturbances affecting habitat structure and frugivores assemblages.