Context dependent song-flight performance and timing in the Black-headed Bunting (Emberiza melanocephala)

Many songbirds produce song-flights; however, the function, vocal and motor characteristics, as well as the diel and seasonal variation of song-flight in songbirds remain not well understood. Here, we studied two types of song-flight in male Black-headed Buntings (Emberiza melanocephala), the Moth — a standard, i.e., perch song produced during a horizontal flight, and the Towering — a specifically structured song produced during a complex ascending and descending flight. While perch song, used during Moth flight, has already been described, here we provide the first description and sonogram representation of the more elaborate and less stereotyped Towering song. While males started to perform Moth song-flights as soon as they arrived at the breeding site, Towering did not start before the female arrival. Males usually delivered spontaneous Moth song-flights before chasing rivals or undertaking aerial fights, suggesting Moth is directed towards conspecific males and serves as a threat display. Furthermore, playback of conspecific perch songs triggered males to approach the loudspeaker with Moth song-flights. The Towering started after females arrived at the breeding site, suggesting the Towering is directed towards conspecific females. We detected a seasonal difference in the peak Towering rate between forenoon and afternoon, suggesting that Towerings performed at different times of the day have different functions. Forenoon Towerings were strongly positively related to the number of fertile females at the breeding site, while afternoon Towerings peaked very early in the breeding season and coincided with the number of females at the breeding site before the onset of nest-building. These results provide evidence that birds can direct different types of song-flight towards different receivers and suggest the possibility that time of the day determines the context of the display, namely to attract social mates or solicit copulation. Further work is needed to account for the effect of between male variability in song-flight rate, as well as in height/steepness of flight or song quality.