Post-breeding aggressive territorial behaviour in Eurasian Tree Sparrows (Passer montanus): territory or mate defence? / Pohniezdne agresívne teritoriálne správanie u vrabca poľného (Passer montanus): hájenie teritória alebo partnera?

Abstract

The genetic interests of males and females usually differ. Whenever female fitness depends on an access to limited resources such as male parental care, competitive interactions among females are expected to evolve. There are numerous studies reporting female-female aggression during the breeding season, but this subject has not been examined for the post-breeding period. Here we examine female-female aggression in the Eurasian Tree Sparrow Passer montanus occurring during the autumn courtship period. We show that aggressive behaviour between nest owners and intruders is common and often fierce during the post-breeding courtship period. Importantly, females more frequently perform this behaviour than male nest owners and it is sex- but not age-specific (i.e. birds interfere with individuals of the same sex, but regardless of their age). This study, focusing on the post-breeding period, corroborates the idea that female territorial aggression can be involved in mate monopolization rather than simply serving as a territory defence strategy. Moreover, aggressive territorial behaviour of nest owners towards intruders can also serve as a signal of mate quality during the pair-formation period. We propose that examining female territorial behaviours during the post-breeding period can provide additional insights into the causes of diversity in avian mating systems.

Keywords

• antagonistic behaviour
• sexual conflict
• post-breeding period
• mating systems