Factors influencing the decline of a Bonelli's eagle Hieraaetus fasciatus population in southeastern Spain: demography, habitat or competition?

Abstract

We investigated three possible causes of territory desertion among Bonelli's eagles Hieraaetus fasciatus in Murcia (southeastern Spain): low demographic parameters, low habitat quality and competition with Golden eagles Aquila chrysaetos. From 1983 to 1997, we surveyed a Bonelli's eagle population. Abandoned and occupied territories were compared to find differences in demographic parameters (flight rate, productivity and mortality) or habitat characteristics. Mortality was significantly higher in abandoned territories. Abandoned territories also had larger areas of forest and extensive agriculture, while occupied territories had more shrublands. Competition with Golden eagles was not a determinant of territorial abandonement but interacted with human persecution of the species. Management implications are discussed.