Meeting Abstract
Although photoperiod is widely recognized as the primary environmental cue controlling seasonal reproduction, slight variation in individual timing of breeding can have major fitness consequences in birds. Supplemental cues that fine tune egg-laying date are poorly characterized but are thought to include temperature, food, and social factors. A recent study suggested that social cues (presence of a male partner) can have direct effects the female reproductive axis (vitellogenesis and follicle maturation) in European starlings (Sturnus vulgaris) breeding in semi-natural outdoor aviaries (Perfito et al. 2015). Although many studies have experimentally manipulated song and/or the social environment of breeding birds, few appear to have investigated female responses, specifically timing of egg-laying. We conducted a two-year field study investigating the relationship between female breeding behavior and male presence, song rate, and song quality in free-living European starlings. During the month preceding laying, we surveyed social behavior using visual observation, while simultaneously recording bird song for analysis in Raven. In the second year we experimentally increased the stimulus of male song by playing high quality song at nest boxes. Preliminary results show large variation in song rate among nest boxes (0-32 songs/30 min), with length of the song bout highly correlated with song quality. Male behavior was strongly correlated to female activity at the nest box but not to lay date. Experimental manipulation of song increased activity at the song-treated boxes in terms of male presence and male song rate. We will discuss natural variation in pre-breeding social behavior as well as results from experimental manipulation, and its possible effects on female breeding phenology.
