Editing Arctic tern (section)

== Reproduction ==
[[File:Eidersperrwerk 18.05.2013 13-19-06.jpg|thumb|Nesting with an egg in [[Schleswig-Holstein]], Germany|alt=One tern nesting with an egg in [[Schleswig-Holstein]], Germany]]
[[File:Arctic tern nesting on Iceland.jpg|thumb|Southern Iceland|alt=Terns in flight in southern Iceland]]
Breeding begins around the third or fourth year.<ref name="Hawksley"/> Arctic terns mate for life and, in most cases, return to the same colony each year.<ref name="Firefly p 267"/> [[Courtship in animals|Courtship]] is elaborate, especially in birds nesting for the first time.<ref name="Firefly p 268"/> Courtship begins with a so-called "high flight", where a female will chase the male to a high altitude and then slowly descend. This display is followed by "fish flights", where the male will offer fish to the female. Courtship on the ground involves strutting with a raised tail and lowered wings. After this, both birds will usually fly and circle each other.<ref name="Firefly p 268"/>

Both sexes agree on a site for a nest, and both will defend the site. During this time, the male continues to feed the female. Mating occurs shortly after this.<ref name="Firefly p 268"/> Breeding takes place in [[seabird colony|colonies]] on coasts, islands and occasionally inland on [[tundra]] near water. It often forms mixed flocks with the [[common tern]]. It lays from one to three [[egg (biology)|eggs]] per clutch, most often two.<ref name="HBW"/>

It is one of the most aggressive terns, fiercely defensive of its nest and young. It will attack humans and large predators, usually striking the top or back of the head. Although it is too small to cause serious injury to an animal of a human's size, it is still capable of drawing blood, and is capable of repelling many raptorial birds, polar bears<ref>{{cite web |url=http://channel.nationalgeographic.com/wild/videos/arctic-bird-attack/ |title=Arctic Bird Attack - Nat Geo WILD |access-date=2016-11-26 |url-status=dead |archive-url=https://web.archive.org/web/20161127023843/http://channel.nationalgeographic.com/wild/videos/arctic-bird-attack/ |archive-date=27 November 2016}}</ref> and smaller mammalian predators such as foxes and cats.<ref name="Cramp"/>

The nest is usually a depression in the ground, which may or may not be lined with bits of grass or similar materials. The eggs are mottled and camouflaged.<ref name="HBW"/> Both sexes share incubation duties. The young hatch after 22–27 days and [[fledge]] after 21–24 days.<ref name="HBW"/> If the parents are disturbed and flush from the nest frequently the incubation period could be extended to as long as 34 days.<ref name="Hatch et al."/>

When hatched, the chicks are [[Down feather|downy]]. Being [[precocial]], the chicks begin to move around and explore their surroundings within one to three days after hatching.<ref name="Kaufman"/> Usually they do not stray far from the nest. Chicks are brooded by the adults for the first ten days after hatching.<ref name=Klaassen/> Both parents care for hatchlings.<ref name="HBW"/> Chick diets always include fish, and parents selectively bring larger prey items to chicks than they eat themselves.<ref name="Hatch et al."/> Males bring more food than females. Feeding by the parents lasts for roughly a month before being weaned off slowly.<ref name="HBW"/> After fledging, the juveniles learn to feed themselves, including the difficult method of plunge-diving.<ref name="Firefly p 269"/> They will fly south to winter with the help of their parents.<ref name="Audubon"/>

Arctic terns are long-lived birds that spend considerable time raising only a few young, and are thus said to be [[R/K selection theory|K-selected]].<ref name="Burger"/>  A 1957 study in the [[Farne Islands]] estimated an annual survival rate of 82%.<ref name="Cullen"/>
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