Grebes: Podicipediformes

Grebes stand anywhere from 8.7 to 29.9 inches (22 to 76 centimeters) tall and weigh between 3.5 and 56 ounces (100 to 1,600 grams). The appearance and color in both sexes of these diving birds are similar, though the female is usually smaller. Their coloration varies, depending on whether or not they are breeding. Their wings are rather short and skinny. Their eyes may be yellow, red, or brown, and their bills are short. Because their feet have adapted, changed over time, to swimming, they are unable to walk well on land and can do so only for short distances.

Although their weight remains basically the same throughout their lives, their body mass distribution changes on a yearly cycle. When flight is needed, breast muscle is built up. When frequent diving is required, leg muscle is developed. And when flight feathers are shed each year, huge quantities of fat are deposited because grebes eat feathers. Eating these feathers gives their stomachs a protective lining against the many parasites that inhabit the grebes' bodies. As many as thirty thousand parasites have been counted on one grebe.