St Kilda

Effects of artificial lights and moonlight on petrels at St Kilda

Artificial lights at St Kilda attract petrels, particularly when moonlight is scarce, but deliberate light reduction measures significantly decrease this attraction and its negative impacts. The study found that while reductions in artificial lighting effectively lowered the number of Leach's Storm-petrels drawn to lights, their effect on Manx Shearwaters was less pronounced. Mortality rates were extremely low, with only juveniles affected, primarily after nights with minimal moonlight. Although the overall numbers of petrels attracted were small compared to breeding populations, light reduction measures remained beneficial in preventing disorientation and grounding during fledging periods. This phenomenon is rare in other UK breeding areas, highlighting St Kilda's unique vulnerability.