Diverging responses to natural and anthropogenic habitats in aftrotropical birds and butterflies

Abstract

Species respond differently to landscape structures and environmental changes. In nature conservation, however, responses of a few indicator groups are often generalised to the ecosystem level. In this study, we analyse how birds and butterflies respond to identical landscape structures and environmental gradients across a habitat mosaic in southern Kenya. The study area represents natural coastal forest (forest interior and forest edge) as well as different agro-environments (such as orchards and pastures), which partly may also be suitable surrogate habitats for forest species. We assessed birds and butterflies during the same time along identical line transects, covering the dry and the rainy season. The obtained results indicate that both species groups depict habitat types in some aspects similarly but in others in somewhat different ways. Thus, strongest differences in community similarity were visible between forest interior and the open landscape like pastures for both taxa. The forest community strongly overlapped with orchards for birds but less so for butterflies. Thus, orchards in close geographic proximity to natural forests might be a possible surrogate habitat for certain forest bird species, but less so for more sedentary forest butterfly species. The temporal variation in species richness, abundances, and community structures was much stronger for butterflies compared to birds. Thus, seasonality in tropical ecosystems has to be considered especially when interpreting community structures of butterflies, but much less so in birds. In general, birds and butterflies proved to be suitable indicator groups to evaluate ecologically landscape structures in East Africa, with birds more representing the landscape level and butterflies more the fine-grained habitat scale.