Local climate variability, phenology and morphological traits of the long distance migrants Savis warbler Locustella luscinioides and Sedge warbler Acrocephalus schoenobaenus in reedbeds of a man-made wetland in SE Iberia.

Abstract

As a consequence of climatic variability in the northern hemisphere, the Mediterranean region is experiencing the most pronounced effects of rising temperatures and decreasing precipitation. This has a multitude of effects on bird migration, with particular relevance to migratory passerines associated with wetlands, whose area has been in decline in this region since the last century. In order to relate phenology to morphology and climate in two species of trans-Saharan migrants closely associated with reedbeds, this study analysed the relationships between Savis warblers Locustella luscinioides and Sedge warblers Acrocephalus schoenobaenus abundances, local climatology and morphological traits in an inland coastal artificial wetland in southeastern Iberia over a 12-year period. The climatic variability observed in this wetland was reflected in a negative trend between local temperatures and the year, and a positive trend with annual precipitation. This was confirmed in subsequent series. The abundance of Savis warbler increased adaptively with the year, while that of the Sedge warbler decreased non-adaptively, although neither change was statistically significant. A two-year delay was observed in the interannual phenology peak of the Savis warbler relative to the Sedge warbler. The monthly abundances of Savis warblers exhibited a significant positive correlation with intra-annual temperatures, explaining approximately half of the intra-annual phenology. No morphological trait could be identified as an explanatory factor for these trends, as no significant correlation with year was detected. Consequently, a coincidence with the morphological traits of both species associated with global climate change could not be established, which supports the hypothesis of migratory bird mismatch in the southeastern Iberia. In a future scenario in the eastern fringe of the Iberian Peninsula, an increase in the abundance of some trans-Saharan migrants, such as the Savis warbler, is to be expected as a consequence of climatic improvement, in particular rising temperatures. Further studies are required to ascertain whether this phenomenon occurs in other trans-Saharan migrants in other localities in the west.