Colymbiformes is a disused order of

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

s that was once used to classify

grebe Grebes () are aquatic diving birds in the order Podicipediformes . Grebes are widely distributed freshwater birds, with some species also found in marine habitats during migration and winter. Some flightless species exist as well, most notably ...

s and loons. Scientific study has revealed that these two types of

waterbird A water bird, alternatively waterbird or aquatic bird, is a bird that lives on or around water. In some definitions, the term ''water bird'' is especially applied to birds in freshwater ecosystems, although others make no distinction from seabi ...

s are not so closely related; they have been reclassified in the orders '' Podicipediformes'' and ''

Gaviiformes Gaviiformes is an order of aquatic birds containing the loons or divers and their closest extinct relatives. Modern gaviiformes are found in many parts of North America and northern Eurasia (Europe, Asia and debatably Africa), though prehistoric ...

'', respectively. Grèbe5

References

"Colymbiformes"
''Encyclopædia Britannica''. 2005. Encyclopædia Britannica Premium Service. Bird orders Obsolete bird taxa {{bird-stub