Penguin flippers, skin and feathers

Information on penguins

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This is the second page in the section "Physical characteristics of penguins". The first page describes penguin shape, coloration, head, legs and penguin tail.

Penguin wings / Penguin flippers

Penguin wings are called flippers. They are hard and stiff and look like the wings of an airplane. The flipper bones are solid and heavy. Penguins get propulsed by both the upstroke as the downstroke. Flippers are spreaded out to release body heat when a penguin is too warm.
Penguin spreading its flippers
(Humboldt penguin)

© Thomas De Schampheleire

A penguin wing is called a flipper. It is a hard, rigid paddle covered with tiny stiff feathers that are not waterproof (unlike the feathers on the rest of a penguin body). A penguin flipper has a shape comparable to an airplane's wing.

Birds normally have hollow bones, since little weight helps in flying. Due to the shape of their wings, normal birds only gain speed by the down stroke. Penguins however have solid bones, which are heavier. This helps in buoyancy. In addition, penguins gain speed by both the up and down strokes of their flippers. Because a penguin flipper is so hard, it is also used as a weapon in penguin discussions or fights.

Penguins sometimes spread their wings away from their body. This allows them to cool down on a hot day. Heat can flow away from their flippers since this is practically the only part of the body (together with the feet) that doesn't have a thick plumage to conserve heat.

Penguin skin and penguin feathers

A penguin skin has two layers: a fat layer and a feather layer. The fat layer (also called blubber) is several centimeters thick and helps penguins in staying warm, even in extreme conditions.

The feather layer is the top layer, and also helps in keeping a penguin warm. It is wind- and waterproof thanks to several things. First of all, a penguin feather consists of two parts: a downy and a stiff part. The downy part lays closest to the penguin body and traps an air layer. This air layer serves as an insulating 'buffer' between the penguin body and the cold air. On a warm day, penguins ruffle their feathers to break the insulating air layer, hence cooling down. While swimming in the sea, the water pressure bends the penguin feathers against the body, thinning the air layer thus reducing the insulating effect. However, a penguin will still keep warm thanks to the blubber layer. When the penguin leaves the water, its feathers jump back into place and the air layer is restored.

The part of the feather that actually is seen from the outside, is stiff and small. The feathers overlap each other and are densely packed. There are about 70 feathers per square inch on a penguin's body. That's about 11 feathers per square centimeter, which is more than other birds have.

During the day penguins often preen. Preening consists of cleaning, combing and oiling the feathers. Preening is very important to keep the penguin waterproof. The oil that is spread out over the penguin feathers comes from a gland at the base of its tail. Oil is taken by rubbing the bill against the gland. It is then spread out over the wings.
Preening Humboldt penguins
© Thomas De Schampheleire

Penguins keep their skin wind- and waterproof by spreading natural oil over the stiff part of the feathers. The oil not only serves as an insulation, but it also reduces friction, helping penguins in gliding smoothly through the water.
Oiling feathers is part of a grooming process called preening. Prior to preening, a penguin cleans its feathers (removing dirt and water), and rearranges them. When finished, the penguin starts to oil his feathers. With his bill, the penguin reaches for the oil gland at the base of its tail and takes some by rubbing its bill against the gland. The oil is spread over the feathers by rubbing the bill against them.
Preening is an essential task for a penguin, and it is done at any time during the day. It happens on land, but also in water where it's possible to reach for some difficult spots.

Most penguin species molt once a year, however Galapagos penguins moult twice a year. The feathers come off in patches. During molt, the new feathers grow beneath the old ones. When the new feathers are ready they push the old ones out. This doesn't happen all at once: the feathers come off in patches.
Molting King penguins
© Thomas De Schampheleire

Sometimes penguins preen each other, which is known as allopreening. Allopreening happens between partners, as well as between strangers. It not only serves hygienic and health purposes, but is also a form of social bonding.

Once a year (usually after the breeding season) penguins shed all of their feathers, a process called molting (also written moulting). New feathers grow beneath the old ones and when the new feathers are completely grown they push the old ones out. This way a penguin stays warm during the molt (moult). The old feathers come off in patches. The whole molting process lasts from two to five weeks (depending on the species) and during this time the penguins will not enter the water. They survive on fat reserves that were built up before the molt started.
Galapagos penguins molt twice a year.

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