Dispersal, maturation and recruitment in a long-lived, trans-continentally migrating bird

Abstract

Natal dispersal is a multi-step process. It commences when a juvenile departs from its natal site and concludes when it settles to breed for the first time. During this interim period, dispersing individuals of long-lived species undergo a wandering phase, which may span years. This phase remains one of the least studied aspects of species life history. We utilized a unique GPS-telemetry dataset on a slow-life history migratory bird of prey - the European honey buzzard, tracked for multiple years after fledgling. Our aim was to assess how phenology, ranging behaviour and philopatry change as individuals gain experience. Individuals exhibited variability in the age at which they first returned to their breeding range, yet all survivors settled at sites proximate to their natal nests. In subsequent returns, immatures increased the time spent within the breeding range and narrowed down their ranging to smaller areas situated even closer to their natal nests. Our study unveils the complexity and protraction inherent in natal dispersal, emphasizing the importance of individual experience and migratory improvement for successful recruitment in long-lived species. HIGHLIGHTSO_LIWe used a unique GPS telemetry dataset on honey buzzards to track their natal dispersal and recruitment in this long-lived avian migrant. C_LIO_LIAll individuals gradually decreased their ranging areas, moved closer to natal sites, and increased the time spent on the breeding grounds to synchronize with adults and begin recruitment. C_LIO_LIMortality during return migration was high and acted as a bottleneck. C_LIO_LIWe found both processes to be complex and lengthy, with the overall duration depending on individual decisions regarding the timing of return migration. C_LI