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Providing evidence to improve practice

Individual study: Supplementary feeding improves the breeding success of Spanish imperial eagle Aquila adalberti, west-central Spain

Published source details

González L.M., Margalida A., Sánchez R. & Oria J. (2006) Supplementary feeding as an effective tool for improving breeding success in the Spanish imperial eagle (Aquila adalberti). Biological Conservation, 129, 477-486


This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.

Provide supplementary food for raptors to increase reproductive success Bird Conservation

A replicated before-and-after study in 37 Spanish imperial eagle Aquila adalberti territories in Castilla y León, Castilla-La Mancha, Madrid and Extremadura provinces, Spain (Gonzalez et al. 2006) found that the fledging rate of eagles was significantly higher when territories were supplied with supplementary food, compared to before feeding (average fledging rate of 1.56 young/pair with feeding vs. 0.72 young/pair without, 37 clutches investigated). Siblicide was also lower in fed nests (6% of 50 chicks lost to siblicide in fed nests vs. 45% of 86 in unfed nests) and overall productivity increased in 89% of pairs and declined in just 8%. The increase in fledging rate was even higher in pairs with at least one subadult parent (1.57 young/pair in fed territories vs. 0.54 young/pair in unfed territories) and occurred in both high and low-quality habitats. Food was supplied to territories with more than one chick (and only after the second chick hatched) and consisted of one European rabbit Oryctolagus cuniculus provided every two to three days in territories with three chicks or every four days for two chicks.