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

Authors: Raquel Ponti, Angel Arcones, Xavier Ferrer, and David R. Vieites

Year: 2020

Publication: Journal of Biogeography

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Keywords: bird migration, fossil record, LGM, Species Distribution Models, trans-Saharan migratory birds


Aim: During the Plio-Pleistocene, glacial cycles shaped Northern Hemisphere species’ distributions causing range contractions followed by interglacial expansions. In migratory bird species, climatic changes could result in a rapid reshaping of their ranges and/or migratory behaviour, given their dispersal capacity. In this context, it has been suggested that long-distance North American migratory species could have lost their migratory condition during cold glacial periods, regaining it later in warmer periods. Here, we explored this hypothesis for extant Eurasian-African migratory bird species.
Location: Eurasia and Africa.
Taxon: Migratory birds.
Methods: We used Species Distribution Models (SDMs) to infer the present and Last Glacial Maximum (LGM) potential distribution of 81 Trans-Saharan migratory bird species, and reviewed the available bird fossil record for the Plio-Pleistocene covering Eurasia and Africa.
Results: SDMs predicted a reduction of the northern edges of the breeding ranges during the LGM compared to the present. However, the current wintering ranges were somewhat similar in the Pleistocene, with the Saharan desert belt gap being always present through time, not overlapping with their breeding ranges. The fossil record also supports the persistence of migration during the Pleistocene.
Main conclusions: The palaeo-distributions and absence of medullary bone in Pleistocene fossils from wintering Euro-African migratory species confirm that they were migratory, providing independent support for our models. The hypothesis of the loss of migratory behaviour in these species during the Pleistocene is not supported. Furthermore, the differences in migratory species from Eurasia-Africa and the Americas can be influenced by geographical differences, the persistence of the Mediterranean basin as climatically suitable area during glaciations and the existence of the Saharan belt.

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