Editing Red-throated loon (section)

==Description==
[[File:Gavia stellata -New Jersey -USA-26Feb2009.jpg|thumb|left|An adult in non-breeding plumage shows the speckled back which gives the bird its [[specific name (zoology)|specific name]].|alt=A grey and white bird swims in water.]]

Like the other members of its genus, the red-throated loon is well adapted to its [[aquatic environment]]: its dense [[bone]]s help it to submerge, its legs—in their set-back position—provide excellent propulsion, and its body is long and streamlined. Even its sharply pointed bill may help its underwater streamlining. Its feet are large, its front three toes are fully webbed, and its [[tarsus (skeleton)|tarsus]] is flattened, which reduces drag and allows the leg to move easily through the water.{{sfn|Sibley|Elphick|Dunning|2001|pp=124–25}}

The red-throated loon is the smallest and lightest of the world's loon species, ranging from {{convert|53|to|69|cm|in|abbr=on}} in length{{efn|By convention, length is measured from the tip of the bill to the tip of the tail on a dead bird (or skin) laid on its back.{{sfn|Cramp|1977|p=3}}}}<ref name= "Cornell"/> with a {{convert|91|-|120|cm|in|abbr=on}} [[wingspan]],<ref name = "Cornell"/>{{sfn|Svensson|Grant|1999|p=12}} and weighing {{convert|1|-|2.7|kg|lb|abbr=on}}.<ref name= "Cornell"/> Like all loons, it is long-bodied and short-necked, with its legs set far back on its body.{{sfn|Cramp|1977|p=42}} The sexes are similar in appearance, although males tend to be slightly larger and heavier than females.{{sfn|Carboneras|1992|p=162}} In breeding plumage, the adult has a dark grey head and neck (with narrow black and white stripes on the back of the neck), a triangular red throat patch, white underparts, and a dark grey-brown [[bird anatomy|mantle]].{{sfn|Cramp|1977|p=43}} It is the only loon with an all-dark back in breeding plumage.{{sfn|Carboneras|1992|p=163}} The non-breeding [[plumage]] is drabber with the chin, foreneck, and much of the face white, the top of the head and back of the neck grey, and considerable white speckling on the dark mantle.{{sfn|Cramp|1977|p=43}} Its [[iris (anatomy)|iris]] is carmine-red to burgundy in colour, its legs are black on the outer half and pale on the inner half, and the webs of its feet are pinkish-brown, with darker margins.{{sfn|Carboneras|1992|p=171}}

Its bill is thin, straight, and sharp, and often held at an uptilted angle.{{sfn|Cramp|1977|p=43}} One of the bird's North American [[folk name]]s is pegging-awl loon, a reference to its sharply pointed bill, which resembles a sailmaker's [[stitching awl|awl]] (a tool also known as a "pegging awl" in [[New England]]).{{sfn|Cassidy|Hall|2002|p=84}} Though the colour of the bill changes from black in summer to pale grey in winter, the timing of the colour change does not necessarily correspond to that of the bird's overall plumage change. The [[nostrils]] are narrow slits located near the base of the bill.{{sfn|Cramp|1977|p=42}}

[[File:Gavia stellata -Iceland -swimming-8.jpg|right|thumb|In breeding plumage, the adult shows the red throat that gives the species its common name.]]
[[File:Red-Throated Loon Juvenile.jpg|thumb|Very young birds are covered with dark brown or grey [[down feather]]s.|alt=Dark grey fuzzy-looking chick floats on water.]]
When it first emerges from its egg, the young red-throated loon is covered with fine soft [[down feather]]s. Primarily dark brown to dark grey above, it is slightly paler on the sides of its head and neck, as well as on its throat, chest, and flanks, with a pale grey lower breast and belly. Within weeks, this first down is replaced by a second, paler set of down feathers, which are in turn replaced by developing juvenile feathers.{{sfn|Cramp|1977|p=49}} The juvenile's plumage is similar to that of the adult, though with a few distinguishing features. It has a darker forehead and neck, with heavy speckling on the sides of the neck and the throat. Its back is browner and less speckled, and its underparts are tinged with brown. Its eyes are reddish-brown, and its beak is a pale grey. Though some young birds hold this plumage until mid-winter, many quickly become virtually indistinguishable from adults, except for their paler bills.{{sfn|Cramp|1977|p=43}}

[[File:Plongeon catmarin en vol vectorisé.svg|thumb|In flight, the hunchbacked profile of the red-throated loon is distinctive.|alt=diagram of silhouette of red-throated loon in flight]]
In flight, the red-throated loon has a distinctive profile; its small feet do not project far past the end of its body, its head and neck droop below the horizontal (giving the flying bird a distinctly hunchbacked shape) and its thin wings are angled back. It has a quicker, deeper wingbeat than do other loons.{{sfn|Sibley|2000|p=23}}

===Voice===
The adult red-throated loon has a number of [[bird vocalization|vocalisations]], which are used in different circumstances. In flight, when passing [[conspecific]]s or circling its own pond, it gives a series of rapid yet rhythmic [[goose]]-like cackles—''kaa-kaa-kaa'' or ''kak-kak-kak'', at roughly five calls per second. Its warning call, if disturbed by humans or onshore [[predator]]s, is a short croaking bark. A low-pitched moaning call, used primarily as a contact call between mates and between parents and young, but also during [[animal sexual behavior|copulation]], is made with the bill closed. The species also has a short wailing call—''aarOOao...aarOOao...''—which descends slightly in [[pitch (music)|pitch]] and lasts about a second; due to strong [[harmonic]]s surrounding the primary pitch, this meowing call is more musical than its other calls. Another call—a harsh, pulsed cooing that rises and falls in pitch, and is typically repeated up to 10&nbsp;times in a row—is used in territorial encounters and pair-bonding, and by parent birds encouraging their young to move on land between bodies of water.{{sfn|Cramp|1977|p=48}} Known as the "long call", it is often given in duet, which is unusual among the loons;{{sfn|Carboneras|1992|p=164}} the female's contribution is longer and softer than her mate's.{{sfn|Cramp|1977|p=48}}

Young have a shrill closed-bill call, which they use in begging and to contact their parents. They also have a long call used in response to (and similar to that of) the long call of adults.{{sfn|Cramp|1977|p=48}}

===Similar species===
At medium to close range, an adult red-throated loon in either breeding or non-breeding plumage is usually easily recognised. However, in certain light conditions, at certain times in its moulting cycle, or at greater distances, it may be mistaken for another species—most commonly the [[black-throated loon]], but also occasionally the [[great crested grebe]]. It shows more white on the head and neck than does the black-throated loon, and—provided it is not sitting low in the water—tends to show more white on the flanks as well. If it is sitting lower in the water, so that the white on the flanks is reduced to a patch on the rear flank (thus resembling the pattern of the black-throated loon), that patch tends to be less clearly defined than the comparative patch on the black-throated.{{sfn|Appleby|Madge|Mullarney|1986}}