Boletín de la RSEHN. Sección Biológica

El búho real, Bubo bubo (Linnaeus, 1758) se considera un generalista trófico aunque puede especializarse en consumir aquellas presas que sean más abundantes. En ocasiones puede incluir otras rapaces en su dieta, habiendo una preocupación cada vez mayor sobre cómo podría afectar a las especies protegidas. El objetivo del estudio es conocer la presencia de rapaces en la dieta de búho real en el centro de la Península Ibérica. Para ello, se tomaron muestras de egagrópilas y otros restos de presas en diferentes localidades de la provincia de Madrid. La presa más frecuente fue el conejo (60,08% de las capturas y 90,23% de la biomasa ingerida), mientras que la incidencia de las rapaces en la dieta se caracteriza por ser prácticamente irrelevante (1,84% de las capturas y 1,16% de la biomasa), como se ha documentado en otros estudios. A pesar de haber rapaces disponibles, la alta frecuencia y biomasa aportada por el conejo sugiere que es su presa principal, de forma que la presión por parte del búho real sobre otras rapaces se podría considerar leve y sólo será más importante en aquellas zonas donde la abundancia de rapaces sea alta o donde falte su presa principal.

The Eagle-owl Bubo bubo is considered a trophic generalist, although it can consume those preys that are more abundant. Sometimes it can include other raptors in its diet, having one growing concern, on how it could affect these protected species. While the diet of Eagle-owl has been extensively studied, few works addressed these interactions among predators. It has been speculated that it may be a matter of competition. Eliminating the potential competitors would provide greater availability to its main prey, the European rabbit Oryctolagus cuniculus. The objective of the study is to know the presence of raptors in the diet of Eagle-owls in the central Iberian Peninsula. In this area the rabbit is not a limiting factor in the eagle-owl diet. We collected samples of pellets and other remnants of prey in different localities of Madrid. An analysis of prey number and biomass consumed was subsequently made. For the identification of the remains of food, was consulted specific bibliography and scientific reference collection of the species present in the study area. Some 1,250 prey remains were analyzed and about 51 species different prey were identified. The most frequent prey was the rabbit (60.08% of catches and 90.23% of the biomass consumed). On the other hand the presence of birds of prey in the diet was almost irrelevant (1.84% of catches and 1.16% of biomass). Despite having birds of prey available, high frequency and biomass contributed by the rabbit suggests that it is their main prey. So, the Eagle-owl from other raptors consumption, could be considered mild and only will be more important in those areas where the abundance of raptors is high or where is missing its main prey. The main conclusions derived from this study are as follows:

1) Eagle-owl has a very wide food-spectrum. It is a generalist predator of medium and small-sized prey, although it can specialize in certain species more frequents, 2) Rabbits are the most important prey in the study area, 3) Pigeons and rodents assume an important contribution of diet to the owl in the study area. The presence of agricultural-lands and urban areas favors the presence of large populations of these animals, 4) Raptors are not an important contribution in the Eagle-owl diet, nor quantitatively or based on the biomass, 5) The importance of raptors in the Eagle-owl diet is similar than the documented for other Mediterranean regions. In the study area the rabbit is not a limiting factor in the Eagle-owl diet.