Regulation of the Dependence Period in Booted Eagles: Effects of Nutritional Conditions

The post-fledging dependence period is a crucial stage in the development of altricial birds that may condition their future performance and fitness. This period is regulated by parental investment, in terms of food provisioning and protection, and young demands associated to their development and physical condition. We examine the post fledging dependence regulation in 21 nestlings Booted Eagle (Aquila pennata) in southern Spain. We compare the dependence timing among juvenile birds from different territories. Here, we analyzed blood plasma chemistry of nestlings in southern Spain and compared blood bi-ochemistry parameters, including urea levels, and a body condition index with hatching date. Urea levels showed a stronger negative relationship with the length of dependence period than did not showed the hatching date or the body condition index. Our results support that better nourished nestlings attain independence latter than those in a worse condition, highlighting the potential of urea levels as a reliable indicator of nestling status. In this study, we describe concentrations of selected chemical parameters in plasma of free living nestling of Booted Eagles, including chemical parameters that have been shown to be related to nutritional condition. Young with a better nutritional conditions started dis-persal latter. Blood parameters can be used as a very useful complementary technique when approaching ecological issues. Early dispersal onset seems to be controlled by en-dogenous factors evolutionary selected since it should provide inherent benefits in terms of future fitness.