Post-fledging survival and dispersal of the White-throated Dipper Cinclus cinclus

The post-fledging period is still an understudied stage of avian life cycle, even in the case of otherwise frequently studied species. The general breeding biology of the White-throated Dipper is known well, but only a few studies have focused on survival and dispersal during the post-fledging period. In this study we report on results revealed by radio-telemetry, a method which has not been used in the species to date. Nestlings (37 individuals from 9 nests) in a mountain population of central Slovakia were radio-tagged on the mean expected fledging age (22 days post-hatch) and monitored daily until death, disappearance or reaching independence. Only 22-32% (depending on the handling of uncertain data) of fledglings survived the first 12 days post-fledging. Predation was the most frequently suspected cause of death. The daily survival rate was markedly lower during the first two days after fledging (0.717-0.758) than later (0.914-0.941). The daily movement distance remained stable during the first week post-fledging and increased around the age of reaching independence (c. 12 days post-fledging). On the other hand, the distance from the natal nest and the within-brood distance (length of river occupied by fledglings from the same nest) increased gradually since fledging. We propose that in our study population the low post-fledging survival could be potentially balanced by frequent renesting and/or double-brooding, timing of which corresponds well with the age of reaching independence when juvenile birds disperse outside the natal territory.