Low breeding propensity and success of European Turtle Doves in Germany

Abstract Understanding the breeding success of European Turtle Doves is crucial for their conservation, helping to address the threats they face, and optimizing the species’ prospects for future successful reproduction and survival. However, data on breeding success of this species in Germany are missing due to the low density and poor accessibility of nests and chance to disturb nesting efforts during direct nest searches. We therefore used two indirect methods to obtain data on breeding success. First, we analyzed field age ratios, i.e. the proportion of juveniles from Citizen Science data. We observed a marked decrease in observed fledglings from 1.28 in the years 1957-1989 to 0.44 in 1990-2009 and to 0.32 in 2010-2023. This suggests a sharp decline in breeding success. Very low juvenile numbers in July further suggest that first broods were especially affected. Second, nesting sites were determined from GPS data, and the breeding constancy was checked at these sites. Based on data from 32 GPS-marked birds representing 28 breeding pairs, we obtained values of maximum breeding success of 1.5 chicks per potential breeding pair at hatching and 0.7 chicks per potential breeding pair at fledging. This is an optimistic calculation for fledglings, as it assumes that two chicks per nest survive until fledging. Overall, these data highlight an urgent need to improve the habitat conditions in the breeding areas to conserve this once common species. Competing Interest Statement The authors have declared no competing interest. Footnotes Emails: hannes.russ{at}bio.uni-giessen.de, yvonne.r.schumm{at}bio.uni-giessen.de, uta.m.gerz{at}bio.uni-giessen.de, ben.lanius{at}gmail.com