Using observed seabird fallout records to infer patterns of attraction to artificial light

Abstract

Attraction of fledgling shearwaters, petrels, and storm-petrels to artificial light has been documented for decades on islands around the world and is considered a significant threat to many species. Although large numbers of downed birds have been observed after being disoriented by light, several important elements of this ‘fallout’ phenomenon are unknown, including the locations along the path from nest to ocean at which attraction and/or disorientation occurs and whether fledglings can be attracted back to land after reaching the ocean in numbers large enough to contribute significantly to fallout. To investigate these questions, we compared observed Newell’s shearwater Puffinus newelli fallout records (from 1998 to 2009) on Kauai, USA, with expected numbers generated from several hypothetical models containing basic assumptions related to fledgling movement and attraction to light. Based on our results, the spatial pattern of observed fallout is consistent with the amount of light that fledglings may view along their first flights to and beyond the coastline. This suggests that even fledglings from dark regions of the island may not be safe because they may view light after reaching the ocean and still be susceptible to attraction. These findings support recent modeling efforts predicting that most birds fledging from Kauai are likely exposed to at least some anthropogenic light. As nocturnal use of light by humans is unlikely to be eliminated, research on the types of artificial light that are both useful to humans and safe for seabirds may be crucial for the conservation of these important marine animals.