Stopover Ecology of the European Turtle Dove (Streptopelia turtur), a Threatened Migratory Bird Species, after the Crossing of an Extended Ecological Barrier

Simple Summary: The European Turtle Dove (Streptopelia turtur) is a declining migratory species that overwinters in sub-Saharan Africa and migrates to Europe each spring to breed. Most of the knowledge regarding its wintering grounds, the routes it follows and the sites where it rests and regains mass between migration flights has been obtained from the west and central European populations. In this study, we combined long-term bird ringing data, tracking data and citizen science data to estimate the numbers of Turtle Doves that migrate through Greece every spring and increase our knowledge of how the species uses resting sites after crossing the Mediterranean Sea. Approximately 16% of the European population migrates through Greece every spring, between the end of March and the end of May. On average, Turtle Doves arrive with very low body mass, and some stay on the resting sites for as long as three weeks to regain the mass loss. The extensive use of resting sites after the Mediterranean Sea indicates the probable importance of such sites for the species. Migratory routes, important stopover sites and wintering grounds for the Turtle Dove, a declining trans-Saharan migratory bird, are known mainly for populations in western and central Europe, but very little is known about birds using the eastern migration flyway. By combining long-term ringing data, tracking data and citizen science data, a comprehensive picture of the stopover ecology of the Turtle Dove's spring migration in the eastern Mediterranean is presented. Furthermore, a quantitative estimate of the number of birds that migrate over Greece during the spring migration is given. Approximately 16% of the European population migrates through Greece, passing through as early as the end of March, with the passage lasting up to the end of May. On average, the species arrives depleted after the crossing of the Sahara Desert and the Mediterranean Sea, with no systematic refuelling event taking place in North Africa. Both tracking and ringing data indicate that the birds undergo an extensive stopover after the barrier crossing (as much as close to three weeks). Turtle Doves additionally show significant body mass gain during their stay, indicating the potential importance of stopover sites after the Mediterranean Sea for the conservation of the species.