King penguins constantly prune feathers. Like all birds, they molt - and in the Antarctic, the energy requirements are substantial. Adult king penguins annually fast ashore for 1 month for molting. By the end of molt, they have lost 44% of their prefasting body mass. About 18% of new feather synthesis occurs at sea, thus reducing both nutrient requirement and fasting duration. Credit for research, and for further information: "Energy and protein requirements for molt in the king penguin Aptenodytes patagonicus."
Cherel Y, Charrassin JB, Challet E.
king penguin moltpruning feathers