Every cm² penguin skin is covered with 12 feathers. The feathers are 3 cm long, slightly bent and become regular cleaned and oiled.
Directly on the skin you find downy feathers, imbricately placed, forming the so called "thermo-underwear".
They're there to keep the body warm. (see thermal insulation
Above them lay the oiled upper feathers, forming a waterproof "wetsuit".
The wing-coverts have no downy undercoat and are very stiff.
They are used for propulsion during swimming.(see flippers).
Although they say penguins are black and white, this is not completely true. Often their back has a blue shining, instead of black.
Each feather has a more or less blue spot at the end. Especially at little and king penguins this blue shine is very striking.
But that blue shine, very clear direct after moulting, will become more matt grey or brown during the year.
And the white of their bellies will turn to filthy yellow.
In opposite to our hair, feathers only grow for a short while and then remain unchanged.
While they need to protect a penguin against cold, water and sharp cliffs, they wear a lot.
Therefore a penguin has to renew his feathers every year after breeding: called moulting
They have to stuff a lot of food, while during moult they can't go to sea for food.
During the moulting period (about three weeks), their feathers aren't waterproof so they would freeze and drown.
Besides they wouldn't be fast enough too to catch their food.
During that period, the old feathers are pushed out by the underneath growing new ones and fall out.
The penguins look depressing and when they finally have their new feathercoat,
this seems too large because they lost so much weight (till a third of their entire body weight) during the three weeks lasting moulting period.
too, of the several species has its reason: for most birds it serves as camouflage or to recognize congeners
and as communication (as for peacocks).
For a penguin too, communication in the water is important.
But only his head and back is above the water surface, so a coloured body would make no sense. And indeed, the difference between the several species lays in the colour (and form) of the feathers
on the head and on the throat. (see Characteristics
The adelie, gentoo and chinstrap penguins sometimes breed in mixed colonies round Antarctica. They differ by respectively a band on the chin (chinstrap)
or a white spot on the head and orange bill (gentoo). So penguins aren't always only black and white.
And all crested penguins
differ by the form and color of their crest.
Under water penguins all look the same: white front and a black coat.
This also has its reason: it serves as camouflage.
When they swim or dive, the upperside is dark und the underside light.
Predators on the water surface, like sea leopards, can hardly recognize them against the dark background of the sea.
And from below, they look light against the bright surface of the water and so hardly visible too.
This principal is especially used when hunting. African penguins approach a swarm fish from below (very inconspicuous) and then,
unexpected, let brighten up their white fronts. The swarm fish, being startled, breaks apart, so the penguins can easier catch a single fish.