Artificial light at night (ALAN) can negatively impact the behaviour of nocturnally active seabirds by causing disorientation, exhaustion, and injury or mortality from light-induced collisions. Procellariiformes (e.g., petrels, prions, shearwaters, diving petrels and storm petrels) are disproportionately attracted to ALAN compared to other seabird groups, fledglings on their maiden flight are most at risk. The Hauraki Gulf has one of the world’s highest diversities of seabirds, including several threatened species. Many of the species in the region are vulnerable to light pollution. While most of these species breed on uninhabited offshore islands, the extensive shipping activity in this region puts seabirds at great risk of light-induced collisions with vessels as they pass or are anchored nearby. This includes fishing vessels working at night.
The first part of this study, undertaken on two seabird islands, tested which light intensities and colours were least attractive to seabirds through behavioural experiments where we shone lights into the sky and recorded seabird attraction. We also modelled the lights into the visual system of seabirds to identify how seabirds perceive lights differently. Our land-based experiments showed an equal statistical attraction to the light types we tested but provided anecdotal observations where more research and larger sample sizes are required. The number of seabirds trapped in the light beam differed by island and moon phase. The number of seabirds observed in thermal imagery differed by island and moon phase when comparing small LED lights only. Fifteen birds were grounded, most on Pokohinu Burgess Island during the flood LED treatment. Differences between islands likely reflected the local seabird diversity at each island.
The second part of this study, undertaken on vessels either anchored near the Mokohinau Islands or drifting off the eastern Coromandel, tested which light intensities and colours were least attractive to seabirds through behavioural experiments where we shone lights horizontal to the vessel and recorded seabird attraction. Significantly more birds were observed in thermal imagery and from near the Mokohinau Islands than the eastern Coromandel, possibly due to the species present on each of the island groups or the time of year or vessel used during the experiments. Additionally, statistically significant numbers of birds were observed in thermal imagery and in boat-based observations closer to sunset and sunrise than during the middle of the night. Boat-based experiments showed an equal statistical attraction to the light types tested. The logistical challenges and resource constraints were key limitations resulting in small sample sizes.
Further research into the effects of ALAN in the Hauraki Gulf, and globally, is urgently required to address the increasing threat of ALAN to seabirds, especially for those species listed as threatened. The recommendations for future boat-based behavioural experiments should attempt to target specific seabird species that are vulnerable to ALAN, time experiments to incorporate a greater range of moon phases and weather, augment experiments to obtain more data for each treatment (and preferably without confounding variables, such as time of year and location), increase the number of each light type to be more consistent with the level of deck lighting used on fishing vessels, and invest in automation of detection to reduce the labour involved in manually detecting birds in thermal videos.
Lukies, K., Gaskin, C., Gaskett, A., Heswall, A., Gulley, K. and Friesen, M. 2021. Lighting adjustments to mitigate against fishing vessel deck strikes/vessel impacts. MIT2019-03 final report prepared by Northern New Zealand Seabird Trust for the New Zealand Department of Conservation, Wellington. 37 p.