Changes

==Description==

==Description==

Grebes range in length from 11 to 32 inches. They are designed for swimming rather than walking or flying: their feet are set so far back on their bodies that they find walking difficult, and usually prefer to swim - for which the feet provide excellent propulsion. They are often seen swimming with their necks held erect. Their feet are curious for having wide lobes, which help in paddling, rather than webs like those of a [[duck]]. Grebes have a layer of soft, downy [[feather]]s under their outer feathers. They swallow these feathers when [[preening]], and feed them to their young. It is not known why they do this.

Grebes range in length from 8 to 29 inches, and weigh from 5 ounces to 3 pounds, depending on the species. Coloration is a general dark-above/light-below pattern, with principal differences between species in head ornamentation and bill shape. Their feet are not webbed like [[loon]]s, to which they bear a superficial resemblance; rather, each toe is lobed, and propulsion through the water is done with a rapid figure-8 motion, enabling grebes to swim underwater or on the surface at great speed. On land walking is difficult and awkward due to the position of their legs on the body.

Grebes are poor fliers and will usually dive to safety instead of taking off.

Grebes are predatory.  Many species - especially the larger grebes - eat fish, and of these only the Western grebe has a habit of spearing fish with its beak.  The smaller species live nearly-exclusively on invertebrates, such as insects and crustaceans; Pied-billed grebes feed on crayfish, and are the only grebes capable of crushing these hard-bodied shellfish.

Evolutionists consider grebes among the most primitive of birds, closely related to [[loon]]s and [[petrel]]s.

Grebes are also noted for their curious habit of swallowing feathers.  Plucking them from their own bodies, the feathers collect in the pyloric pocket of the stomach and act as a filter, preventing bones and scales from entering the intestinal tract.  The mass of collected indigestible material forms a pellet, which is then regurgitated in a manner similar to owls.  Young grebes are fed feathers by the parents almost immediately after hatching.  

==Species==

==Species==