Little penguins forage at sea by day and return to their burrows at night. Birds gather in rafts offshore and come in together once the light has dropped, moving quickly across exposed sand to the cover of vegetation, rocks or burrows. The group crossings are the basis of the organised nightly viewing at colonies such as Phillip Island in Victoria.
The usual explanation is predation risk on the beach, where a thirty-centimetre penguin has little defence against gulls, raptors and introduced mammals. Consistent with this, arrival timing tracks sunset through the season, and artificial light on landing beaches has been shown to alter when and where birds come ashore, which is why colony lighting is managed carefully.
Unlike most penguins, little penguins nest in burrows or crevices rather than in the open, and adults can be strongly faithful to a particular site across seasons. What is less settled is how much of the nightly grouping is protective and how much is simply the outcome of birds converging on the same landing point at the same hour.