The Rufous-thighed Kite Harpagus diodon is not an endemic breeder of the Atlantic Forest: lessons to assess Wallacean shortfalls

Abstract

The migratory Rufous-thighed Kite Harpagus diodon is widely distributed in South America, and a recent spatiotemporal analysis of its distribution that was largely based on citizen science data concluded that it breeds (almost) exclusively in the Atlantic Forest, constituting a ‘hidden endemism’, and that it is a complete migrant, overwintering in the eastern Amazonian lowlands. However, that study missed key data from large areas that would have resulted in a different biogeographical pattern. Here, we reject the ‘hidden endemism’ hypothesis and show that the Rufous-thighed Kite is a more widespread breeder. We propose that to uncover Wallacean shortfalls of migratory birds correctly, (1) citizen science data must be integrated with thorough bibliographical searches and specimen examination and (2) life-cycle categories should be critically determined: failing to recognize the importance of these two key issues can undermine the ability of researchers to uncover the true extent of breeding ranges and timing of migration, resulting in erroneous ecogeographical patterns. By proposing and following a set of recommendations, and using previously unpublished and published documented records mostly from the southwestern portion of the distribution of Rufous-thighed Kite, we here show that this species breeds in the Cerrado of eastern Bolivia and is present during the austral spring and summer in the Austral Yungas but largely absent during the austral autumn and winter, mirroring the seasonality of the species in the Atlantic Forest.