Highly disparate bird assemblages in sugarcane and pastures: implications for bird conservation in agricultural landscapes

Abstract

Sugarcane and cattle pastures are two of the most widespread and economically important agricultural landscapes. However, in Brazil, they have not been properly investigated for their importance to native birds and wildlife conservation. Thus, we aim to characterize and compare bird assemblages of sugarcane and cattle pastures; and understand how landscape features within both habitats influence bird assemblages. We surveyed birds in both agricultural habitats over one year, and then investigated the relationship between species richness and composition with landscape diversity, matrix permeability, and the size and distribution of natural forests close to both habitats. We observed 132 species in cattle pastures and only 72 in sugarcane (48% bird community similarity). We further evaluated the richness and relative abundance of avian ecological groups, including habitat specialists and habitat generalists, insectivores, omnivores, granivores and frugivores. All avian groups were higher in pastures, the habitat where landscape heterogeneity and number of scattered trees was higher. Our results show that overall increasing landscape heterogeneity favors an assemblage with higher richness and composed by species with more diverse ecological functions. Therefore, we argue in favor of management practices that incorporate heterogeneity in agricultural landscapes, mainly in sugarcane fields where a homogeneous scheme has been used. Otherwise, the potential of agricultural landscapes for bird conservation will be highly hindered, particularly if the sugarcane sector expands to other agricultural lands.