Editing Great auk (section)

===Reproduction===
[[File:Pinguinus.jpg|thumb|upright|left|Nesting ground with juveniles and eggs, by Keulemans]]
Historical descriptions of the great auk breeding behaviour are somewhat unreliable.<ref>{{Cite journal | doi = 10.1111/j.1474-919x.2003.00227.x| title = Remarks on the terminology used to describe developmental behaviour among the auks (Alcidae), with particular reference to that of the Great Auk ''Pinguinus impennis''| journal = Ibis| volume = 146| issue = 2| pages = 231–240| year = 2003| last1 = Gaskell | first1 = J. }}</ref> Great Auks began pairing in early and mid-May.<ref name="BNABreeding">{{Cite web | last = Montevecchi | first = William A. |author2=David A. Kirk | title =Breeding-Great Auk (''Pinguinus impennis'') | work = The Birds of North America Online | publisher = Cornell Lab of Ornithology | year = 1996 | url = http://bna.birds.cornell.edu/bna/species/260/articles/breeding| access-date =29 April 2010 }} {{subscription required}}</ref> They are believed to have mated for life (although some theorize that great auks could have mated outside their pair, a trait seen in the razorbill).<ref name="BNABehavior" /><ref name=Cokinos2000/>{{rp|page=313}} Once paired, they nested at the base of cliffs in colonies, likely where they copulated.<ref name=Crofford_1989/>{{rp|page=28}}<ref name="BNABehavior" /> Mated pairs had a social display in which they bobbed their heads and displayed their white eye patch, bill markings, and yellow mouth.<ref name="BNABehavior" /> These colonies were extremely crowded and dense, with some estimates stating that there was a nesting great auk for every {{convert|1|m2|sqft}} of land.<ref name="BNABehavior" /> These colonies were very social.<ref name="BNABehavior" /> When the colonies included other species of alcid, the great auks were dominant due to their size.<ref name="BNABehavior" />

[[File:Pinguinus impennis eggs Zoothèque MNHN.jpg|thumb|Eggs in [[Muséum national d'histoire naturelle]]]]
Female great auks would lay only one egg each year, between late May and early June, although they could lay a replacement egg if the first one was lost.<ref name=Crofford_1989/>{{rp|page=32}}<ref name="BNABreeding" /> In years when there was a shortage of food, the great auks did not breed.<ref name="BNADemography" /> A single egg was laid on bare ground up to {{convert|100|m|ft}} from shore.<ref name="FOM 1864" /><ref name=Crofford_1989/>{{rp|page=33}} The egg was ovate and elongate in shape, and it averaged {{convert|12.4|cm|in|frac=8|abbr=on}} in length and {{convert|7.6|cm|in|frac=8|abbr=on}} across at the widest point.<ref name="Gaskell">{{cite book|url =https://books.google.com/books?id=tsUzeXV_7jcC&q=egg+%22Great+Auk%22&pg=PA152 |title = Who Killed the Great Auk?| first = Jeremy |last =Gaskell |publisher = Oxford University Press (US)|isbn = 0-19-856478-3 |year = 2000|page= 152}}</ref><ref name=Crofford_1989/>{{rp|page=35}} The egg was yellowish white to light ochre with a varying pattern of black, brown, or greyish spots and lines that often were congregated on the large end.<ref name="FOM 1864" /><ref name="Egg">{{cite web|url=http://www.museums.norfolk.gov.uk/default.asp?Document=300.40.20&Image=577&gst= |title=Great Auk egg |publisher=Norfolk Museums & Archaeology Service |access-date=8 May 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090209223346/http://www.museums.norfolk.gov.uk/default.asp?Document=300.40.20&Image=577&gst= |archive-date=9 February 2009 }}</ref> It is believed that the variation in the egg streaks enabled the parents to recognize their egg among those in the vast colony.<ref name="BNABreeding" /> The pair took turns incubating the egg in an upright position for the 39 to 44 days before the egg hatched, typically in June, although eggs could be present at the colonies as late as August.<ref name=Crofford_1989/>{{rp|page=35}}<ref name="BNABreeding" />

The parents also took turns feeding their chick. According to one account, the chick was covered with grey down.<ref name=Cokinos2000/>{{rp|page=313}} The young bird took only two or three weeks to mature enough to abandon the nest and land for the water, typically around the middle of July.<ref name=Crofford_1989/>{{rp|page=35}}<ref name="BNABreeding" /> The parents cared for their young after they fledged, and adults would be seen swimming with their young perched on their backs.<ref name="BNABreeding" /> Great auks matured sexually when they were four to seven years old.<ref name="BNADemography">{{Cite web | last = Montevecchi | first = William A. |author2=David A. Kirk | title =Demography-Great Auk (''Pinguinus impennis'') | work = The Birds of North America Online | publisher = Cornell Lab of Ornithology | year = 1996 | url = http://bna.birds.cornell.edu/bna/species/260/articles/demography| access-date =29 April 2010 }}</ref>