The lunar cycle affects at-sea behaviour in a pelagic seabird, the streaked shearwater, Calonectris leucomelas

The lunar cycle has been shown to affect the behaviour of a variety of marine animals. However, changes in the behaviour of seabirds and marine mammals and how they respond to the lunar cycle have been less well documented, principally because of the technical difficulties in long-term recording of their at-sea behaviour. Because seabirds generally rely on visual cues at small spatial scales, ambient light levels by moonlight may have a strong influence on their foraging and predator avoidance behaviours at sea at night. We used global location sensor loggers attached to wintering streaked shearwaters to examine whether the birds' at-sea behaviour varied with the lunar phase. The shearwaters migrated from Japan to the seas off northern New Guinea. Their activities at night changed synchronously with the lunar phase: birds flew for longer periods and landed on water more frequently on nights with a full moon than when there was a new moon. Our results indicate that at-sea behaviour of pelagic seabirds is closely associated with the lunar cycle.