Aims: The feeding of Montagu's Harriers Circus pygargus during the breeding period was studied in relation to the land-use systems (agricultural or pasture-lands) in pseudosteppe areas of Extremadura (SW Spain).
Methods: A total of 1,180 prey items was identified from the combined analysis of pellets and prey remains collected in nests and perches of the species.
Results: Biases in diet results from the use of pellets (insects overrepresented) or remains (vertebrates, birds and mammals, overrepresented). Significant differences in the feeding of harriers between the two land-use systems were demonstrated. Hence, large insects (mainly grasshoppers) showed a higher importance in agricultural pseudosteppe areas than in pasture-lands dedicated to extensive livestock, with respect both the number of prey (82% vs. 67%) and prey weight (26% vs. 16%). On the contrary, in pasture-land areas birds and mammals contributed to a higher number of prey (32% vs. 18%) than in agrosystems, but this did not represented a higher relative importance in biomass (80% vs. 72%). Harriers take both larger and more diverse preys in pastures-lands than in agrosystems.
Conclusions: The relative availability of the distinct prey categories between the two land-use systems appeared to be the main factor involving these differences among localities. These results and their implications discussed for the ecology and conservation of the Montagu's Harrier in Mediterranean areas.
