Aggressive behaviour in Montagu's harrier (Circus pygargus) during the breeding season

Abstract

Abstract Intra and interspecific aggressive behaviour of Montagu's harrier was studied during the breeding seasons 1987–1990. Of the intraspecific aggressive interactions the most frequent one is the ≪attack≫, mainly in relation to territory defence. The area defended by nesters against conspecifics averaged 4.0 hectares and aggressivity was more intense near the nest. Female resulted always more aggressive than males. In the defence of pair bond and of territory intruders of the other sex are widely tolerated while females are always more attacked than males. In the interspecific interactions Montagu's harrier was relatively tolerant against other species, even if raptors, present in the breeding area, while also against potential predators of eggs and nestlings, like carrion crow, it seems quite very tolerant. A non aggressivedisplay, ≪communal soaring≫, has been described in Montagu's harriers for the first time.