Lack of evidence of a Pleistocene migratory switch in current bird long-distance migrants between Eurasia and Africa

Aim: During the Plio-Pleistocene, glacial cycles shaped Northern Hemisphere species' distributions causing range contractions followed by interglacial expansions. In bird migratory species, climatic changes could result in a rapid re-shape of their distribution ranges and/or migratory behaviour, given their movement capacity. In this context, it has been suggested that long-distance North American migratory species could have lost their migratory condition during cold periods regaining it later in warmer periods. Here, we explored this hypothesis in Eurasian-African extant migratory bird species. Location: Europe and Africa Taxon: migratory birds Methods: We used Species Distribution Models to infer the present and Last Glacial Maximum (LGM) distribution of 81 trans-Saharan bird migratory species and we revised the available fossil record for the Plio-Pleistocene covering Europe and Africa. Results: Our results show a southwards reduction of the breeding distributions during the LGM compared to the present. However, the current wintering areas were somehow similar in the Pleistocene, with the Saharan belt gap always present through time, not overlapping with their breeding ranges. Main conclusions: The paleo-distributions and absence of medullary bone in Pleistocene fossils from wintering African migratory species confirm that they were migratory, providing independent support for our models that suggest the same. The hypothesis of the loss of migratory condition in these species during the Pleistocene can be rejected.