Feather stable isotopes (δ2Hf and δ13Cf) identify the Sub-Saharan wintering grounds of turtle doves from Europe

Conservation of migratory birds requires knowledge of breeding and nonbreeding ranges and the connections between them. European turtle doves (Streptopelia turtur) are Palearctic-African long-distance migrants with wintering areas in the Sub-Saharan belt that are classed as vulnerable due to strong population declines. However, detailed non-breeding locations of individuals from different migratory flyways are unknown. To identify wintering regions of turtle doves, we measured stable isotopes of feathers grown on the wintering grounds and used a dual-isotope (hydrogen (δ2Hf) and carbon (δ13Cf)) probabilistic assignment to analyse origins of individuals migrating through the western and central/eastern flyways. The most probable wintering areas for turtle dove samples from both flyways were in the western and central Sub-Sahara. However, we found differences in δ2Hf and δ13Cf values between turtle doves following different migratory routes (western vs central/eastern flyway). This result suggests a higher likelihood of origins in the central Sub-Sahara for central and eastern migrants, while turtle doves using the western flyway originated primarily in the western Sub-Sahara, highlighting the importance of both regions for the future conservation of turtle doves from European breeding populations. The establishment of migratory connectivity of populations requires sampling from birds from the European as well as Asian continent; however, we provide important results that can be used to test hypotheses regarding population declines resulting from factors experienced over the full annual cycle for some populations.