Two cases of tits’ fights to the death in competition for winter roosting sites

Abstract

Finding a suitable place for overnight roosting may be crucial for survival during winter. If the number of suitable roosting sites is limited, intra- and interspecific competition may occur. In a nest box group, two cases of tit deaths were recorded in a winter season. The tits had apparent beak marks from pecks on their heads, and so were probably killed by other birds roosting in the boxes. Both dead individuals (a Blue Tit and young female of Great Tit) were competitively weaker individuals considering the hierarchy among wintering tits. They did not belong to the local winter flock. Presence of bird droppings on the bodies of the killed tits indicates that after the fight an individual (probably the winner of the competition) still roosted in the box. In both cases there was at least 57.7% of boxes that were not used by birds, suggesting that the birds fought for the best roosting sites. To the best of our knowledge, these are the first records concerning birds fighting for roosting sites during the winter season, which resulted in a death of one of the competing individuals.