Sexual and seasonal variation in territorial behaviour of kestrels, Falco tinnunculus

Abstract

Territorial behaviour among male and female European kestrels was examined by simulating intrusions of conspecifics. An adult, caged decoy kestrel, male or female, was presented to wild birds. During late courtship as well as after the eggs hatched, resident males responded with overt aggression in contests with other males near the nest. Females showed less intense aggression in intra-sexual encounters shortly before laying commenced than before or after this period. After the eggs hatched, the intensity of female aggression in intra-sexual encounters was related to brood size. In inter-sexual encounters near the nest during early and late courtship, many females solicited the decoy male. In the non-breeding season, the intensity of territorial aggression increased, independently of sex and of age of the birds, from early autumn to late autumn/early winter and persisted at a high level throughout the winter.