Diet of the Mediterranean Golden Eagle (Aquila chrysaetos homeyeri Severtzov, 1888) and adult behaviour during the breeding season in Central Spain.

Abstract

We studied the diet and behaviour of Mediterranean Golden Eagle (Aquila chrysaetos homeyeri Severtzov, 1888) in Central Spain by analysing 106,292 images obtained from motion-activated cameras installed at 24 nests during the breeding season of 2017 and 2018. A total of 32 different prey species were identified, being the European rabbit, the Iberian hare and the Common Wood Pigeon the most frequently consumed preys. Mammals were the most important prey group, both in terms of frequency and useable biomass, even though they were less important than in other regions of the species distribution area.
Adult behaviour results showed that both, females and males, delivered preys to the nests in a similar proportion, while some differences were observed in type, age and size of the preys captured by each sex. In addition, as the eaglets grew, the biomass provided by both sexes decreased significantly. Furthermore, the amount of biomass delivered to nests with two eaglets was significantly higher than that delivered to nests with one eaglet. Finally, females were almost entirely in charge of attending the eaglets at the nest, reducing this activity as chicks got older.
In addition, diet composition varied depending on the altitude and predominant land use of the territory. For example, the number of mammals delivered to the nests decreased significantly with increasing altitude, while the total biomass supplied remained constant. This can be explained as adults delivered less number of artiodactyls (with higher useable biomass) at higher altitudes and more lagomorphs (with lower useable biomass) at lower altitudes. Prey diversity was also higher at greater altitudes, which was explained, in part, by the higher diversity of reptiles delivered. In relation to land use, Mediterranean Golden Eagles showed a more generalist diet in those territories where their traditional preys (i.e. European rabbit, Red-legged Partridge) were scarce.
Ultimately, this study provides new evidence about the remarkable resilience of Mediterranean Golden Eagle in the Iberian Peninsula, having adapted its diet in territories where deep changes in prey availability have taken place. Thus, some preys with little historical importance for the species, such as roe deer, seem to be a key component of their diet nowadays.