This bird steals the penguin's eggs. There is usually one Skua for every 10,000 penguins. The sheath bill is a scavenger who feeds off dead penguins. The sheath bills also distract adults and swoop down to steal baby chicks. Mammals also pose a threat to penguins.
Seals are the primary predators of the penguin in the water.
Penguins fear seals so much that they will jump out of the water if they see a dark spot. One seal was found to have 18 penguins in their digestive tract. Orcas are also penguin predators. They, however, are not as great a threat to penguins because they eat a variety of food. Mankind is most destructive to penguins especially the humboldt pengins.