The family Gaviidae includes 5 species found in North America.

Loons breed on freshwater lakes and ponds in the northern Holarctic and winter in coastal waters and bays in the northern hemisphere. They are large aquatic birds (53-100 cm long, 1-6 kg weight) that come on land only to nest. They have straight, sharp-pointed bills, webbed feet, short wings and a short tail. The legs are set so far back that they cannot stand upright on land. Breeding plumages are strikingly patterned, mainly black, white and gray with contrasting spotting and barring. Winter plumages are dull, gray and white. 

Food is mainly fish, but crustaceans, aquatic insects and larvae, frogs and some plant material are also taken. Mollusks and other invertebrates, as well as fish, are eaten during the winter in marine habitats. Loons feed by diving and underwater pursuit of fish; often form cooperative flocks for fishing, especially during migration and in winter. The nest site is chosen by the male on open land next to the water or in shallow water; often on an island in a lake or pond. The nest is usually a low mound of plant material with a shallow depression; sometimes little or no nest material is used. Both sexes build the nest which may be used in subsequent years. Clutch usually 2 olive-brown or olive-green eggs with dark spots; laid at interval of 1-3 days. They hatch asynchronously. Both sexes incubate for 24-30 days. Downy hatchlings are semi-precocial and immediately enter the water; brooded ashore for the first few nights. They are taken on the adult's back in the water or warmed under the wing during the day. Both parents feed the chicks and continue to do so until after fledging at 55-75 days of age. In most species the adults obtain food close to nest. The Red-throated flies to the ocean or a nearby river. Fish are carried crosswise in the bill to feed the young for several weeks, then less frequently until fledging at 55-75 days. Age at maturity is 2-3 years.