Migratory birds occupy different geographical areas during breeding and non‐breeding periods, and thus different factors may determine their range limits depending on each season. One such factor is the spatial climatic component of the niche, which is widely used to model species distributions, yet the temporal component is often neglected and is generally assumed to be constant. We tested the hypothesis that the climatic niche is conserved between breeding and non‐breeding areas in 355 bird species migrating through Eurasian–African flyways. For this, we performed niche overlap analyses and compared niche differences between sister or phylogenetically closely related species, as well as linking the differences to migratory distances. For more than 80% of the species, there was no or very little overlap between their breeding and non‐breeding climatic niches. For most closely related species, the degree of overlap of their breeding climatic niches was larger than the overlap observed within each species, but not for their wintering climatic niches, suggesting a phylogenetic conservation of breeding climatic niches. Finally, there was a clear negative relationship between migratory distances and climatic niche overlap within each species. Our results confirmed that the climatic niche of most Eurasian–African migratory species differs between both breeding and non‐breeding ranges, suggesting distinctive seasonal climatic requirements. Given these results and the geographically uneven effects of climate change, the impact of global change is likely to have different effects in each seasonal range. Hence, both breeding and non‐breeding climatic data need to be considered when using species distribution models.

Aim Spatio‐temporal changes have likely caused range fragmentation and population isolation, which could have given rise to the observed current intraspecific differentiation in some species. Here, we test several hypotheses on the potential effect of Pleistocene glacial cycles in the diversification of Arctic shorebird species, comparing between different scenarios of fragmentation of the breeding distribution during glacial and interglacial periods. Location Global. Taxon Arctic migratory shorebirds. Methods We performed species distribution models (SDMs) to explore the changes in the breeding and non‐breeding ranges of 69 species between the last glacial maximum (c. 21,000 years ago) and the present. We also included independent evidence from the fossil record and estimations on the potential extension of the tundra during glacial periods to validate the results from the SDMs. We assigned each species to one of four potential scenarios based on fragmentation and potential recolonization patterns of their breeding ranges during glaciations. Results Our findings show that most of the species with subspecies experienced fragmentation of their ranges during the glacial, the interglacial or both periods. Meanwhile, the majority of the monotypic species maintained their ranges as a continuum. Moreover, the impacts of glacial cycles in the distribution were not homogeneous across the Arctic, and some regions were more prone to the fragmentation of breeding ranges than others. Main conclusions Our work suggests that Pleistocene climatic cycles drove the diversification of Arctic shorebirds by creating allopatric breeding distributions. While the fragmentation of the breeding ranges occurred mainly during glacial periods, interglacials also played a part in maintaining or establishing newly isolated breeding populations for many species. Furthermore, species' distribution changes varied between different regions and habitats, which determined current shorebird diversity patterns.

The evolution of migration in birds and its causes are still subject of debate. Recent studies tracking current bird migration have identified peaks in net primary productivity (NPP) as a main driver of bird migratory behaviour. However, it is unclear which variables may have played a major role in the evolution of bird migration at deeper phylogenetic levels. Here, we used phylogenetic comparative methods to assess whether the evolutionary patterns of migratory distances, as a proxy for migratory behaviour, are correlated with several biometric, climatic and productivity variables in a phylogenetic context, using Sylvia warblers as a case study. Our results recover NPP in the breeding range and during the breeding season as the variable with stronger positive correlation with migratory distances, being always included in the best models considering all potential variables. Several climatic variables show a correlation with the evolution of migration, but those are also tightly correlated with NPP. Among morphological variables, migratory lineages tend to have longer wings than sedentary ones. Although NPP has been identified as a driver of migratory behaviour in current species, in a phylogenetic scale it is not possible to disentangle if it was a main driver in the evolution of bird migratory behaviour or a consequence of it, yet migration and NPP seem to be tightly related today and along the long evolutionary history of these passerines.