Wintering areas on the move in the face of warmer winters

摘要

For several decades, there have been changes in the distance of bird migration. The Eurasian Reed Warbler Acrocephalus scirpaceus is a Trans-Saharan migratory species, which, as recent records suggest, is increasingly wintering in the Iberian Peninsula. This study investigated the strength of the influence of climate on the wintering of this insectivorous species in the Iberian Peninsula, and also used geospatial modelling to identify the most favourable areas. The model was constructed to identify the most relevant explanatory factors ofthis distribution and it was assessed by applying calibration and discrimination criteria, and the influence of each factor was analysed using variation partitioning. The minimum winter temperature is the most relevant factor affecting sites suitable for the wintering of this species in Europe. The best areas are located in the southern and eastern coasts of the Iberian Peninsula and in some locations on the northern Atlantic coast of Spain. Spatial trends analysis corroborated the orientation of the flight paths of the species from their breeding areas to their wintering areas. Topography refined the model in that it is associated with habitat selection at a fine-scale. As the case of the Eurasian Reed Warbler is not unique, the results show the role of the Iberian Peninsula as a new wintering site for species usually wintering in the Sub-Saharan region, modifying their wintering strategy from Trans-Saharan to Pre-Saharan migrants, and whether the recent increase in temperature is the main cause.