Illustration of the wintering and breeding areas and migration directions of five bird species. Breeding (green) and wintering (light brown) areas for some bird species included in the study, based on Cramp and Perrins [36–38]. Arrows show the main direction of movements from wintering areas towards breeding areas during spring migration. Great Reed Warbler A. arundinaceus. The locations of Capri (C) and Antikythira (A) bird observatories in Italy and Greece, respectively, are shown by white squares.