On the trophic and spatial relationships between wintering Red Kites (Milvus milvus) and Marsh Harriers (Circus aeruginosus) in the Guadalquivir Marshes

Abstract

Trophic and spatial variables are studied after pellet analysis from both species. Kites fed mostly on birds and insects, while Harriers fed on small mammals and rats. Prey of Kites were small or big sized but Harriers mainly fed on medium sized prey. The aquatic habitat was the most used by both raptors. Niche breadths were always larger for Kites. Spatial niche overlap was very high but trophic niche overlaps were lower, mainly when considering the biomass of prey size classes. Factors influencing interspecific competition between both species are discussed.