Timing of natal nests is an important factor affecting return rates of juvenile Great Reed Warblers

Abstract

In many bird species, return rates tend to be greatest in the vicinity of their hatching site, thus natal philopatry is an important trait in avian demography. In the present study, we examined how conditions in natal nests affect return rates and dispersal distances of a long-distance migratory passerine. From 2008 to 2016, we studied a colour-ringed population of the Great Reed Warbler Acrocephalus arundinaceus breeding in southeastern Czech Republic. Almost 10% of the 1430 ringed individuals returned to the study site within 2 years after fledging. Birds originating from earlier broods were more likely to return than birds from delayed broods. The variation in local dispersal distances was explained by the sex of the recruits: males dispersed shorter distances than females. There was no evidence that return rates and dispersal distances in Great Reed Warbler are related to other factors closely linked to the condition in the natal nest, namely brood social status and brood size. While the higher return rates of the juveniles from earlier broods is in concordance with the findings of other studies, the sex-related difference in dispersal distances does not correspond with what was found in Great Reed Warbler juveniles in other studies and adults at the same study site. Our results show that early breeding produces more local recruits and that sex-biased dispersal may be site specific.