How penguins stay warm and dry
The downy under portion of the feathers traps a layer of air against the skin. This layer of air is then warmed by body heat, much the way our body heats the air in a down jacket. Their feathers overlap like shingles on a roof and form a barrier, keeping water away from the skin. Penguins also have a layer of blubber, or fat, under the skin. As a rule, larger penguins live in colder areas. This is because larger, rounder bodies lose heat slower than smaller, slimmer bodies. This explains why Antarctica’s emperor penguins, which survive the harshest winters, are the largest penguins in the world.
How penguins stay cool
Some penguin species have bare patches (heat windows) around their eyes. These areas have no feathers and allow excess heat to escape. The patches become very pink when the penguin is warm. Penguins can voluntarily raise their feathers to let the warm air escape. Penguins have many tiny blood vessels (capillaries) close to the skin on their wings, which helps them to cool down by just holding their wings out and letting the air move across them. Penguins can release heat through their feet, where they have a counter-current blood exchange system.
How they swim
A streamlined body, webbed feet and oar-like wings enable penguins to shoot through the water at speeds up to 15 miles per hour. It is often said that penguins look like they are flying through the water. Underwater quickness and the ability to hold their breath aid penguins in catching prey. All penguins use their short, stiff wings for propulsion and their webbed feet for steering. The position of their feet on the lower part the body aids in both steering and hydrodynamics.
How they hide
As mentioned before, penguins have black backs and white bellies. This pattern of coloration is called countershading and serves to camouflage the bird when it is in the water. Since penguins spend most of their time in the ocean, this coloration is an effective form of protection. Countershading also helps the penguins hunt with more success.
How they dive deeper
Most birds have hollow bones, making them lighter for flying. Penguins, however, have solid bones, making them heavier and making it easier to dive underwater for food.
How they shake off the salt
Penguins have almond-shaped glands beneath the skin above their eyes that help them filter out the excess salt from the ocean. The salt drips down their beak, the penguins make a sneeze-like sound, and they are able to shake it off.