What they do in the shadows: partial nocturnality in a large forest parrot

Approximately 97% of all bird species are considered diurnal, although diel activity patterns of birds may be more flexible than previously believed. Much remains unknown about nocturnal activity in typically diurnal birds, which may result in potential loss of information about an important aspect of their behavior and ecology. Parrots (Order Psittaciformes), except for the truly nocturnal species, are generally not known to be active at night. However, Kākā (Nestor meridionalis) is an interesting candidate to understand how nocturnal investigations can challenge the preconceptions of avian activity patterns. Kākā are large forest parrots endemic to Aotearoa New Zealand, with historical and anecdotal evidence of remaining active after dark. We conducted the first field study to assess the activity of wild Kākā during both night and day, using ad libitum and instantaneous sampling techniques. In 122 sampling hours, we recorded 326 Kākā encounters, 17.5% of which occurred at night. In addition to resting, Kākā were observed moving through and flying above the canopy, grooming, and foraging nocturnally. The estimated percentages of observed behaviors differed between sampling techniques, as higher estimates of relatively inconspicuous behaviors, such as resting, were detected using instantaneous sampling. Kākā vocalized during day and night, with high-pitched, long-distance calls being predominant at both times of day. Nocturnal call rates were unrelated to moon phases. Our findings suggest that Kākā exhibit partial nocturnality, which is an unexplored aspect of parrot ecology with implications for conservation and habitat management. Paying greater attention to nocturnal behaviors in typically diurnal species may offer valuable insights for conservation in response to artificial light at night and noise pollution in a rapidly urbanizing environment.