Grebes are small, stout, aquatic birds. They are excellent divers and swimmers, and are able to lower themselves in the water until only their head or bill shows by altering their specific gravity. Most grebes have slender, pointed bills and most adults have crests on their heads during the breeding season. They all have lobed toes, which are not fully webbed. Although they are essentially tailless, some species have vestigial tail feathers. Like loons, their legs are far back on their body and therefore they move awkwardly on land.