Ecological drivers of variation in the extent of the post-fledgling dependence period in raptors

The post-fledgling dependence period (PFDP) is a fundamental stage in the life cycle of altricial birds that determines their long-term survival and fitness. However, research on the duration of this period in raptors, and on the global factors affecting it, is scarce. We performed the first-of-its-kind 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 contrasted to the species and population levels. The length of the PFDP is only 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 in lower latitudes showed longer PFDPs, as well as 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 time available for this period. Results highlight the importance of encouraging the study of this key, but poorly known, life cycle stage of raptors.

Methods
We ran a complete literature search (03/02/2023) using Scopus, Google Scholar and Web of Science, with the key words “post-fledgling dependence period”, “dependence period”, “independence”, “onset of dispersal” and “onset of migration”, paired with the generic common names of the raptors: “eagle”, “hawk”, “buzzard” and “kite”, using also the Spanish translations. 

Additional information on species-specific data (e.g., body weight, clutch size) was obtained from Birds of the World (2022).

The dataset added here corresponds to all the valid studies used for the manuscript. The dataset per species (processed with a meta-analysis via metafor package in R) is already available in the supplementary material (Supporting information).