Loons, also known as divers in Europe, belong to the family Gaviidae. There are five extant species of loons:

1. Red-throated Loon (Gavia stellata): The smallest and most widely distributed loon, it has a distinctive red throat patch during the breeding season. It breeds in the Arctic regions of North America and Eurasia and winters along coastlines.

2. Arctic Loon (Gavia arctica): Also known as the Black-throated Loon, it has a black throat in its breeding plumage. It breeds in northern Europe and Asia and winters along coasts of the northern Pacific and Atlantic Oceans.

3. Pacific Loon (Gavia pacifica): Similar in appearance to the Arctic Loon but slightly smaller, it breeds in the Arctic regions of North America and northeastern Russia and winters along the Pacific coast of North America.

4. Yellow-billed Loon (Gavia adamsii): The largest loon species, it has a distinctive yellow bill. It breeds in the Arctic and sub-Arctic regions and winters in the coastal waters of the North Pacific and North Atlantic Oceans.

These species are adapted to life in cold northern waters and exhibit similar behaviors, such as excellent diving capabilities and distinct vocalizations.