Editing Common loon (section)

{{short description|Freshwater bird native to North America and Western Europe}}
{{Lead rewrite|date=May 2025}}
{{good article}}
{{speciesbox
| image = Gavia immer -Minocqua, Wisconsin, USA -swimming-8.jpg
| image_caption = Adult in breeding plumage in [[Minocqua, Wisconsin]]
| image2 = Loon, common 04-24 a.jpg
| image2_caption=In non-breeding plumage in [[Sunset Beach, North Carolina]]
| status = LC
| status_system = IUCN3.1
| status_ref = <ref name="iucn status 19 November 2021">{{cite iucn |author=BirdLife International |date=2018 |title=''Gavia immer'' |volume=2018 |page=e.T22697842A132607418 |doi=10.2305/IUCN.UK.2018-2.RLTS.T22697842A132607418.en |access-date=19 November 2021}}</ref>
| genus = Gavia
| species = immer
| authority = ([[Morten Thrane Brünnich|Brünnich]], 1764)
| range_map = Gavia immer map 2.svg
| range_map_caption = Approximate distribution map
{{leftlegend|#ff6600|Breeding}}
{{leftlegend|#ffd42a|Migration}}
{{leftlegend|#5f8dd3|Nonbreeding}}
| synonyms = *''Colymbus immer'' {{small|Brunnich, 1764}}
*''Colymbus glacialis'' {{small|Linnaeus, 1766}}
| synonyms_ref = <ref name="hbw2" />
}}

The '''common loon''' or '''great northern diver''' ('''''Gavia immer''''') is a large member of the [[loon]], or diver, [[family (biology)|family]] of birds. [[Reproduction|Breeding]] adults have a [[plumage]] that includes a broad black head and neck with a greenish, purplish, or bluish sheen, blackish or blackish-grey [[upperparts]], and pure white [[Anatomical terms of location|underparts]] except some black on the [[undertail covert]]s and vent. Non-breeding adults are brownish with a dark neck and head marked with dark grey-brown. Their upperparts are dark brownish-grey with an unclear pattern of squares on the shoulders, and the underparts, lower face, chin, and throat are whitish. The sexes look alike, though males are significantly heavier than females. During the breeding season, loons live on lakes and other waterways in Canada, the northern United States (including [[Alaska]]), and southern parts of [[Greenland]] and Iceland. Small numbers breed on [[Svalbard]] and sporadically elsewhere in Arctic Eurasia. Common loons winter on both coasts of the US as far south as Mexico, and on the Atlantic coast of Europe.

Common loons eat a variety of animal prey including fish, [[crustacean]]s, insect larvae, [[Mollusca|molluscs]], and occasionally aquatic plant life. They swallow most of their prey underwater, where it is caught, but some larger items are first brought to the surface. Loons are [[Monogamy in animals|monogamous]]; that is, a single female and male often together defend a territory and may breed together for a decade or more. Both members of a pair build a large nest out of dead [[Hymenachne|marsh grasses]] and other plants formed into a mound along the vegetated shores of lakes. A single brood is raised each year from a clutch of one or two olive-brown oval [[Bird egg|eggs]] with dark brown spots which are [[Egg incubation|incubated]] for about 28 days by both parents. Fed by both parents, the chicks [[fledge]] in 70 to 77 days. The chicks are capable of diving underwater when just a few days old, and they fly to their wintering areas before ice forms in the fall.

The common loon is assessed as a species of [[Least-concern species|least concern]] on the [[IUCN Red List of Endangered Species]]. It is one of the species to which the [[Agreement on the Conservation of African-Eurasian Migratory Waterbirds]] applies. The [[United States Forest Service]] has designated the common loon a species of special status because of threats from habitat loss and toxic metal poisoning in its US range.

The common loon is the [[List of Canadian provincial and territorial symbols|provincial bird]] of [[Ontario]], and it appears on Canadian currency, including the [[Loonie|one-dollar "loonie"]] coin and a previous series of [[Canadian twenty-dollar note|$20 bills]]. In 1961, it was designated the [[List of U.S. state birds|state bird]] of [[Minnesota]], and appears on the Minnesota [[State Quarter]] and the state [[Seal of Minnesota]].