They usually dig deep burrows into grassy banks to form their nests and to protect against land based predators. For birds, preening entails a great deal of feather maintenance. Although penguins do not fly, feathers must be sufficiently groomed to prevent water infiltration. This is a crucial fact of penguin biology since maintaining a high degree of air insulation is vital to survival for some penguins. In the early morning hours before feeding time, Humboldt penguins spend that time preening, both on land and water.
Penguins gather oil from a preening gland located in the rump, from where the tail originates.
Additionally, a penguin will enter the water and preen various regions of the body. Following this preening, the penguin will rub the flipper over the region while rotating its body as it coasts along in the water. It appears as if the penguin is side-stroking. Often, one penguin may preen another penguin. Another aspect of self-maintenance is huddling.