Sequencing the New Zealand dawn chorus: can song playback alter the timing of song initiation?

Abstract

The dawn chorus of songbirds is a behavioural phenomenon occurring prior to sunrise; birds of many different species sing simultaneously at rapid rates. Avian physiology, social behaviours and local environment all influence the onset of dawn song. The influence of social cues on dawn chorus singing is poorly delineated relative to the effect of environmental or physiological factors; in particular, our knowledge of the role of heterospecific cues is limited. In this study, I aimed to determine if New Zealand songbirds would chorus in a distinct order, like those seen in other countries. I investigated whether the timing of song onset relative to sunrise would change as the breeding season progressed. I also assessed if conspecific and heterospecific acoustic cues influence a species’ start time. Finally, I explored the influence of acoustic cues from an early singer, the Tui (Prosthemadera novaeseelandiae) and a late singer, the Riroriro (Grey Warbler; Gerygone igata) on start time. I recorded the dawn chorus at nine sites at the Maungatautari reserve between September and November 2016, using arrays of time-synchronised autonomous recording devices. I broadcast different playback stimuli at three arrays per morning; an early singer, a late singer, and noise. My results suggest that New Zealand dawn choruses follow an order and that the timing of chorus start time changes over time as the breeding season progresses. Tui began singing earliest, and their start time shifted much earlier as the breeding season progressed. Most species joined the chorus in a highly interchangeable order within the same 12 minute window, while Pōpokatea (Whitehead; Mohoua albicilla) sang last. Start time was not found to shift in response to any playback stimuli for any species. The onset of Tui or Riroriro song is unlikely to be used as a cue by either con- or heterospecific neighbours to initiate their own dawn song.