Leach’s Storm-Petrels fledge on the full moon and throughout the lunar cycle

Many seabirds are attracted to anthropogenic light, and the risk is greater for recent fledglings. Lunar phase predicts the probability of stranding, but it remains uncertain whether lunar phase is associated with when young seabirds fledge. Fledging behaviour of nocturnal, burrowing seabirds can be difficult to monitor using traditional methods but can provide insight into environmental factors that influence the risk of stranding. We used passive integrated transponder tags to monitor the fledging dates and times of Leach’s Storm-Petrel chicks from four breeding seasons at a major colony in Newfoundland and Labrador, Canada. We also assessed whether lunar phase associated with fledging date. The median fledge time was 2.4 h after sunset (1.4 - 12.4 h). The median fledge date was 10 October, and fledging dates ranged from 13 September to 13 November. Most importantly, Leach’s Storm-Petrels chicks did fledge during the full moon. These results provide insight into why storm-petrels are less attracted to anthropogenic light during high levels of natural illumination and can be used to inform periods of higher risk for stranding, thus allowing better concentration of conservation efforts.