Ecological drivers of variation in the extent of the post-fledging dependence period in the largest group of diurnal raptors

Abstract

The post-fledging dependence period (PFDP) is a fundamental stage in the life cycle of altricial birds that influences their long-term survival and fitness. However, research on the duration of this period in raptors, and on the factors affecting it, is scarce. We performed the first literature review on the length of the PFDP in Accipitridae, the largest family among diurnal raptors, and a meta-analysis examining the effects of breeding latitude and hemisphere, body weight and migratory status, controlling for species phylogeny. Hypotheses were tested at the levels of both species and populations. The length of the PFDP is known for less than half of Accipitridae species, with no data for two-thirds of the threatened and near-threatened species. Larger species and individuals breeding at lower latitudes showed a longer PFDP, as did non-migrants and southern-hemisphere breeders. The effect of latitude was more marked in larger species, in resident populations and in southern-hemisphere breeders. This extended PFDP in larger and tropical raptors may promote juvenile survival. Migration timing and the effects of continentality in the northern hemisphere constrain the PFDP. These findings highlight the importance of encouraging the study of this key, but poorly known, life-cycle stage of raptors.