Female and male Blue Tits (Cyanistes caeruleus) sing in response to experimental predator exposition

Female song is recognized to serve a similar function as male song and underlies sexual selection processes; yet certain patterns of the expression of female singing behaviour are not in line with traditional explanations known from male songbirds. In particular, in northern hemisphere songbirds, female singing behaviour is regarded to occur only rarely, and; therefore, studies investigating it are sparse. Within the framework of an experimental study on nest defence behaviour, we observed female singing in a common European passerine, namely, the Blue Tit (Cyanistes caeruleus). Females expressed singing behaviour when a dummy of a Sparrow Hawk was exposed to the nest, raising the idea that song might be multifunctional in this species.