Diverging responses to environmental change and different landscape structure 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 (core and margins) as well as different agro-environments (orchards and pastures), which partly may also be suitable surrogate habitats for forest species. We assessed birds and butterflies during the same time and along identical transects, covering the dry and rainy season. The obtained results indicate that both indicator 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 open landscape (i.e. pastures) for both taxa. The forest community strongly overlapped with orchards for birds but less so for butterflies. Thus, orchards in close geographic context with natural forests might be possible surrogates for certain forest bird species but less so for the little mobile 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 when interpreting community structures of butterflies but much less so in birds. In general, birds and butterflies proved to be suitable indicator groups to ecologically assess landscape structures in East Africa, with birds more representing the landscape level and butterflies more the fine-grained habitat scale.