Under cover of darkness: Refuge from artificial light at night may mitigate risks to stranded seabirds

ABSTRACT Artificial light at night is an anthropogenic pollutant that has wide-ranging effects on wildlife. Fledgling seabirds of order Procellariiformes exhibit phototaxis toward artificial lights on their first flights from the nest, causing them to become grounded in human settlements, where they are subject to increased predation risk. Limited evidence suggests certain light types may be less attractive than others, yet there is also evidence for an aversion to light under certain circumstances. We investigated differences in phototactic behavior, activity level, and shelter-seeking behavior of grounded Hydrobates leucorhous (Leach’s Storm-Petrel) fledglings exposed to artificial light in 3 experiments: a Y-maze choice experiment, an open field test, and a modified open field test with a hide box provided (“safe haven test”). When provided with combinations of different light types in the Y-maze, storm-petrels typically remained stationary in the darkest parts of the apparatus (farthest from light stimuli) and exhibited no preferred response toward one light type over another. This was consistent with results from the open field test: individuals were less active in darkness than when exposed to 2 of 3 light conditions (warm white light-emitting diode and high-pressure sodium). More than half of individuals entered the hide box in light conditions, compared to none in darkness. Considered together, our results indicate that most (but not all) H. leucorhous fledglings exhibit photophobic behavior after stranding, which may be part of a behavioral strategy to avoid predation. Further, we demonstrate the utility of providing hide boxes to protect stranded seabird fledglings in locations where lighting cannot be eliminated or where rescue efforts are limited in spatial or temporal coverage. However, hide boxes would have limited utility in dark locations. Hide boxes constitute a novel mitigation measure that merits future testing for its ability to reduce stranding-induced mortality, especially in imperiled procellariiform species.