Navigating the night: effects of artificial light on the behaviour of Atlantic puffin fledglings

Every year in Newfoundland, young Atlantic puffins, Fratercula arctica , departing their nests at night for the first time become stranded in towns near their breeding colonies, a phenomenon thought to be caused by attraction towards artificial light. To test this hypothesis, we conducted three behavioural experiments. First, we illuminated beaches near a breeding colony to determine whether more fledglings would become stranded in illuminated versus dark conditions. Next, we conducted a Y-maze experiment to test stranded fledglings for phototactic behaviour in general and for preferences among high-pressure sodium (HPS), Warm white light-emitting diode (LED), Cool white LED, Blue LED and Orange LED light. Lastly, we quantified activity levels of stranded fledglings in an open field test during exposure to several different light types. We found significantly more fledglings stranded when beaches were illuminated, and fledglings significantly preferred light over darkness in the Y-maze, supporting our hypothesis that Atlantic puffin fledglings become stranded due to light attraction. Fledglings displayed no preferences for certain light types over others in the Y-maze, potentially suggesting that strandings in this species may not be mitigable by changing the streetlight type in stranding-prone towns. Interestingly, fledglings exhibited higher activity levels in darkness and HPS light than in LED light, potentially holding implications for rescue, rehabilitation and husbandry programmes. Overall, our findings demonstrate that the only evidence-based strategy for the reduction of Atlantic puffin strandings is the reduction of coastal artificial lighting; however, further research is needed to determine whether aspects of artificial light besides bulb type may be altered to effectively reduce light attraction in this species. • Atlantic puffin fledglings become stranded in towns near their breeding colonies. • More fledglings became stranded at experimentally lit beaches than at dark ones. • Fledglings preferred light over darkness in a choice experiment. • Light spectrum had no effect on fledgling preferences. • Fledglings were less active under LED light than under darkness or other light types.