Individual and environmental effects on the spatial and temporal extent of the post-fledging dependence period in an endangered neotropical raptor

In altricial birds, the post-fledging dependence period (PFDP) is a fundamental life-history stage with direct consequences for survival, dispersal, and future reproduction. Understanding the drivers of its variation is therefore crucial to developing effective management strategies. However, this information is lacking for most species of conservation concern and/or breeding in the Southern Hemisphere. We describe, for the first time, the PFDP of the Chaco eagle Buteogallus coronatus, an Endangered neotropical raptor. Using location data from 29 GPS-tagged fledglings, we analyzed the duration of the PFDP and the ranging areas occupied as a function of individual sex, body condition, and natal area ecoregion. We also calculated the overlap in space usage among juveniles born in the same territory but in different years. The PFDP lasted for more than 8 mo, as expected for a large, slow-developing raptor, during which juveniles covered more than 300 km2. The PFDP was longer for larger females, probably due to slower development of flight skills; this could also explain why males had larger ranging areas. Juveniles born in the ecoregion with denser woodlands occupied larger areas, likely reflecting their preference for open habitats. Better body condition explained earlier dispersal and modulated the effects of sex and ecoregion. Spatial overlap among juveniles born in the same territory reached around 90%, indicating a high consistency in area use across years. Our results help understand the complex factors affecting juvenile space usage during this vulnerable life stage, increasing the capacity for addressing the conservation needs of this species.