Editing Tern (section)

==Description==
[[File:Larosterna inca4.jpg|thumb|The plumage of the [[Inca tern]] is the most atypical of the group.]]

Terns range in size from the [[least tern]], at {{convert|23|cm|in|frac=2|abbr=on}} in length and weighing {{convert|30|–|45|g|oz|frac=16|abbr=on}},<ref name= Maehr>Maehr & Kale (2005) p. 111.</ref><ref name= olsen136>Olsen & Larsson (1995) p. 136.</ref> to the [[Caspian tern]] at {{convert|48|–|56|cm|in|frac=2|abbr=on}}, {{convert|500|–|700|g|oz|abbr=on}}.<ref name= harrisoncasp>Harrison (1988) p. 368.</ref><ref>Olsen & Larsson (1995) p. 25.</ref> They are longer-billed, lighter-bodied, and more streamlined than gulls, and their long tails and long narrow wings give them an elegance in flight. Male and female plumages are identical, although the male can be 2–5% larger than the female and often has a relatively larger bill. Sea terns have deeply forked tails, and at least a shallow "V" is shown by all other species.<ref name= HBW/> The noddies (genus ''Anous'') have unusual notched-wedge shaped tails, the longest tail feathers being the middle-outer, rather than the central or outermost.<ref name= harrison388>Harrison (1988) pp. 387–390.</ref><ref name= Hutton>Hutton & Drummond (2011) p. 226.</ref> Although their legs are short, terns can run well. They rarely swim, despite having webbed feet, usually landing on water only to bathe.<ref name= HBW/>

The majority of sea terns have light grey or white body [[plumage]] as adults, with a black cap to the head. The legs and bill are various combinations of red, orange, yellow, or black depending on species. The pale plumage is conspicuous from a distance at sea, and may attract other birds to a good feeding area for these fish-eating species. When seen against the sky, the white underparts also help to hide the hunting bird from its intended prey. The Inca tern has mainly dark plumage, and three species that mainly eat insects, [[black tern]], [[white-winged tern]], and [[black-bellied tern]], have black underparts in the breeding season. Three of the noddies ([[brown noddy]], [[black noddy]], and [[lesser noddy]]) have dark plumage with a pale head cap, while the other two noddies ([[blue noddy]] and [[grey noddy]], both of which were formerly placed in the genus ''Procelsterna'') have paler grey plumage. The reason for their dark plumage is unknown, but it has been suggested that in tropical areas, where food resources are scarce, the less conspicuous colouration makes it harder for other noddies to detect a feeding bird.<ref name= simmons>{{cite journal | last= Simmons | first= Keith E L | year=1972 | title= Some adaptive features of seabird plumage types | journal= British Birds | volume= 65 | issue =11 | pages=465–479 | url =http://www.britishbirds.co.uk/search?model=pdf&id=4571 }}</ref> Plumage type, especially the head pattern, is linked to the [[Phylogenetics|phylogeny]] of the terns, and the pale-capped, dark-bodied noddies are believed to have diverged earlier than the other genera from an ancestral white-headed gull, followed by the partially black-headed ''[[Onychoprion]]'' and ''[[Sternula]]'' groupings.<ref name= bridge/><ref name="Cerny">{{cite journal |last1=Černý |first1=David |last2=Natale |first2=Rossy |title=Comprehensive taxon sampling and vetted fossils help clarify the time tree of shorebirds (Aves, Charadriiformes) |journal=Molecular Phylogenetics and Evolution |date=2022 |volume=177 |doi=10.1016/j.ympev.2022.107620 |bibcode=2022MolPE.17707620C |url=https://www.sciencedirect.com/science/article/abs/pii/S1055790322002330 |access-date=2024-07-24}}</ref>

Juvenile terns typically have brown- or yellow-tinged upperparts, and the feathers have dark edges that give the plumage a scaly appearance. They have dark bands on the wings and short tails. In most species, the subsequent [[moulting|moult]] does not start until after migration, the plumage then becoming more like the adult, but with some retained juvenile feathers and a white forehead with only a partial dark cap. By the second summer, the appearance is very like the adult, and full mature plumage is usually attained by the third year. After breeding, terns moult into a winter plumage, typically showing a white forehead. Heavily worn or aberrant plumages such as [[melanism]] and [[albinism]] are much rarer in terns than in gulls.<ref>Olsen & Larsson (1995) pp. 6–9.</ref>

=== Voice ===
{{listen|filename=Sterna-hirundo-002.ogg|title=Common tern (80 s)|description=}}
Terns have a wide repertoire of vocalisations. For example, the [[common tern]] has a distinctive [[alarm signal|alarm]], ''kee-yah'', also used as a warning to intruders, and a shorter ''kyar'', given as an individual takes flight in response to a more serious threat; this quietens the usually noisy colony while its residents assess the danger. Other calls include a down-slurred ''keeur'' given when an adult is approaching the nest with a fish, and a ''kip'' uttered during social contact.<ref name=hume68>Hume (1993) pp. 68–75.</ref> Parents and chicks can locate one another by call,<ref name= burton>Burton (1985) p. 123.</ref> and [[sibling]]s also recognise each other's vocalisations from about the twelfth day after hatching, which helps to keep the brood together.<ref name= sibling>{{cite journal | last= Burger | first= Joanna | author2=Gochfeld, Michael| author3=Boarman, William I | year=1988 | title= Experimental evidence for sibling recognition in Common Terns (''Sterna hirundo'') | journal= Auk | volume= 105 | issue = 1 | pages= 142–148 | jstor=4087337 | doi= 10.1093/auk/105.1.142 }}</ref><ref name=Stevenson>{{cite journal |last=Stevenson |first=J G |author2=Hutchison, R E |author3=Hutchison, J B |author4=Bertram B C R |author5= Thorpe, W H  |year=1970 |title=Individual recognition by auditory cues in the Common Tern (''Sterna hirundo'') |journal=Nature |volume=226 |issue=5245 |pages=562–563 |doi=10.1038/226562a0 |pmid=16057385|bibcode=1970Natur.226..562S |s2cid=4181980 }}</ref>

Vocal differences reinforce species separation between closely related birds such as the least and [[little tern]]s,<ref name= Massey>{{cite journal |last= Massey |first= Barbara W |year=1976 |title= Vocal Differences between American Least Terns and the European Little Tern | journal= The Auk | volume= 93| pages=760–773 |jstor=4085004 |issue=4}}</ref> and can help humans distinguish similar species, such as common and [[arctic tern]]s, since flight calls are unique to each species.<ref name= const>Constantine (2006) pp. 73–77.</ref><ref name=burger/>