The little penguin is the smallest and the only penguin species whose activity on land is strictly nocturnal. Thirteen years of attendance data were used to study the effects of sun, moon, and artificial light on the attendance pattern at Phillip Island, Australia. Automated monitoring systems recorded individually marked penguins every time they arrived (after sunset) at or departed (before sunrise) from 2 colonies under different lighting conditions: natural night skylight and artificial lights used to enhance penguin viewing for ecotourism around sunset. Sunlight had a strong effect on attendance as penguins arrived on average around 81 min after sunset and departed around 92 min before sunrise. The effect of moonlight was also strong, its effect was stronger on departure than arrival times. Moonlight could be overridden by artificial light at the artificially lit colony, but the similar attendance patterns between colonies suggest that artificial light did not mask the moonlight effect. informacion[at]ebd.csic.es Rodriguez et al (2016) Waddling on the dark side. Ambient light affects attendance behavior of little penguins. J Biol Rhythms doi: 10.1177/0748730415626010