Range expansion of native thrushes in South America

Abstract

The widespread human activity on Earth exerts strong selective pressures on the species with which we coexist. Faced with constant environmental change, species respond with mechanisms of adaptation, expansion, retraction or displacement. Species that establish new populations outside their former range facilitated by human-induced environmental change are called ‘neonatives’. In this study, we use data from the citizen science platform eBird to describe the range expansion of four thrushes in South America: Turdus amaurochalinus, T. chiguanco, T. falcklandii, and T. rufiventris. We found that thrushes have significantly expanded their range during the last 20 years. Turdus amaurochalinus and T. chiguanco more than duplicated its area whereas the other two species expanded about 1.5-fold their distribution range. As a result of this range expansion, every thrush species now overlaps with the other three at least in part of their distribution area. This expansion is likely to result in novel ecological interactions, affecting other native species in different ways, and also establishing new relationships with productive activities and urban environments. Thrushes provide an opportunity to understand the response of wild species to human change on the planet, and to design conservation strategies adapted to this new reality.