Many species have elaborate courtship flights and displays on the ground, accompanied ny melodious calls. The grebes are highly specialized aquatic birds closely related to one another but to no other known birds, living or fossil. For this reason, the family is included in its own order, the Podicipediformes. Grebes are adapted for diving from the surface and for underwater swimming. Their strong legs are situated at the rear of a rotund or somewhat elongated, virtually tailless body.
Most grebes can fly well, but do so rather infrequently once settled down on a particular water.
Their wings are relatively small, necessitating a fast rate of flapping, and when not in use are usually folded right away under the body plumage. The legs are short and stout with large feet which, like those of the majority of the families within the Pelicaniformes, are fully webbed. The most obvious character by which one can identify pelicans is that of the bill. This is very long, straight, flattened, hooked at the tip, with a large elastic pouch suspended beneath the lower mandible. The diet of the pelican is mainly fish, but crustaceans are sometimes eaten.