Editing Pelican (section)

==Description==
[[File:Pelican-Gaping-Aruba.JPG|thumb|A brown pelican opening mouth and inflating air sac to display tongue and some inner bill anatomy]]
[[File:Pelecanus erythrorhynchos -Tulsa Zoo, Oklahoma, USA-8c.jpg|right|thumb|upright|[[American white pelican]] with knob which develops on bill before the breeding season]]
[[File:Pelecanus occidentalis -Smith Island, Chesapeake Bay, Maryland, USA -nest-8cr.jpg|right|thumb|An adult [[brown pelican]] with a chick in a nest in Chesapeake Bay, [[Maryland]], US: This species will nest on the ground when no suitable trees are available.<ref>{{cite web |url=http://www.floridawildlifeviewing.com/florida_animals_wildlife/PelicanNesting.htm |title=Brown Pelican breeding and nesting habits |access-date=5 August 2012 |work=Florida Wildlife Viewing|publisher=M. Timothy O'Keefe}}</ref>]]
[[File:Australian Pelican showing large pouch.jpg|thumb|[[Australian pelican]] displaying the extent of its throat pouch (Lakes Entrance, Victoria)]]
Pelicans are very large birds with very long bills characterised by a downcurved hook at the end of the upper mandible, and the attachment of a huge [[gular skin|gular]] pouch to the lower. The slender [[Ramus of the mandible|rami]] of the lower bill and the flexible tongue muscles form the pouch into a basket for catching fish, and sometimes rainwater,<ref name=hanzab1a/> though to not hinder the swallowing of large fish, the tongue itself is tiny.<ref>{{cite book |title=The Bird, its Form and Function |author=Beebe, C. William |year=1965|publisher=Dover Publications |location=New York, New York}}</ref> They have a long neck and short stout legs with large, fully webbed feet. Although they are among the heaviest of flying birds,<ref>Elliott (1992), p. 290.</ref> they are relatively light for their apparent bulk because of air pockets in the skeleton and beneath the skin, enabling them to float high in the water.<ref name=hanzab1a/> The tail is short and square.<!-- with 20 to 24 [[retrix|retrices]]. commented out until source available--> The wings are long and broad, suitably shaped for soaring and gliding flight, and have the unusually large number of 30 to 35 secondary [[flight feather]]s.<ref>{{cite book| last = Perrins| first = Christopher M.| title = The Princeton Encyclopedia of Birds| year = 2009| publisher = Princeton University| isbn = 978-0691140704| page = 78 }}</ref>

Males are generally larger than females and have longer bills.<ref name=hanzab1a/> The smallest species is the brown pelican, small individuals of which can be no more than {{convert|2.75|kg|lb|abbr=on}} and {{convert|1.06|m|ft|abbr=on}} long, with a wingspan of as little as {{convert|1.83|m|ft|abbr=on}}. The largest is believed to be the Dalmatian, at up to {{convert|15|kg|lb|abbr=on}} and {{convert|1.83|m|ft|abbr=on}} in length, with a maximum wingspan of {{convert|3|m|ft|abbr=on}}. The Australian pelican's bill may grow up to {{convert|0.5|m|ft|abbr=on}} long in large males,<ref name="hanzab1c">{{cite book| others = Marchant, S.; Higgins, P.J. (Coordinators).| title = Handbook of Australian, New Zealand and Antarctic Birds. Volume 1, Ratites to Ducks| year = 1990| publisher = Oxford University Press| location = Melbourne, Victoria| isbn = 0-19-553068-3| page = 746 }}</ref> the longest of any bird.<ref name=NSS/>

Pelicans have mainly light-coloured plumage, the exceptions being the brown and Peruvian pelicans.<ref name=mb/> The bills, pouches, and bare facial skin of all species become brighter before breeding season commences.<ref name=enc/> The throat pouch of the Californian subspecies of the brown pelican turns bright red, and fades to yellow after the eggs are laid, while the throat pouch of the Peruvian pelican turns blue. The American white pelican grows a prominent knob on its bill that is shed once females have laid eggs.<ref name="Keith05">{{cite journal|title=An Overview of the American White Pelican |author=Keith, James O. |journal= Waterbirds|volume= 28|issue= Special Publication 1: The Biology and Conservation of the American White Pelican |year=2005|pages=9–17|jstor=4132643 | doi = 10.1675/1524-4695(2005)28[9:aootaw]2.0.co;2|s2cid=85813418 }}</ref> The plumage of immature pelicans is darker than that of adults.<ref name="mb">{{cite book|author1=Steele, John H. |author2=Thorpe, Steve A. |author3=Turekian, Karl K. | title = Marine Biology: A Derivative of the Encyclopedia of Ocean Sciences| url = https://books.google.com/books?id=kkRKJCofvXMC| year = 2010| publisher = Academic Press| location = London, United Kingdom| isbn = 978-0-08-096480-5| pages = 524–30 }}</ref> Newly hatched chicks are naked and pink, darkening to grey or black after four to 14 days, then developing a covering of white or grey [[down feather|down]].<ref name=DofB/>

===Air sacs===
Anatomical dissections of two brown pelicans in 1939 showed that pelicans have a network of [[Bird anatomy#Skeletal system|air sacs]] under their skin situated across the ventral surface including the throat, breast, and undersides of the wings, as well as having air sacs in their bones.<ref name="richardson39"/> The air sacs are connected to the airways of the respiratory system, and the pelican can keep its air sacs inflated by closing its [[glottis]], but how air sacs are inflated is not clear.<ref name="richardson39">{{cite journal|last=Richardson|first=Frank|year=1939|title=Functional Aspects of the Pneumatic System of the California Brown Pelican|journal=The Condor|volume=41|issue=1|pages=13–17|url=http://sora.unm.edu/sites/default/files/journals/condor/v041n01/p0013-p0017.pdf|doi=10.2307/1364267|jstor=1364267|access-date=22 February 2013|archive-date=20 November 2018|archive-url=https://web.archive.org/web/20181120044433/https://sora.unm.edu/sites/default/files/journals/condor/v041n01/p0013-p0017.pdf|url-status=dead}}</ref> The air sacs serve to keep the pelican remarkably buoyant in the water<ref>{{cite book| last = Bumstead| first = Pat| title = Canadian Feathers : a Loon-atics Guide to Anting, Mimicry and Dump-nesting| url = https://archive.org/details/canadianfeathers0000bums| url-access = registration| year = 2001| publisher = Simply Wild Publications| location = Calgary, Alberta| isbn = 0968927807| page = [https://archive.org/details/canadianfeathers0000bums/page/129 129] }}</ref> and may also cushion the impact of the pelican's body on the water surface when they dive from flight into water to catch fish.<ref name="richardson39"/> Superficial air sacs may also help to round body contours (especially over the abdomen, where surface protuberances may be caused by viscera changing size and position) to enable the overlying feathers to form more effective heat insulation and also to enable feathers to be held in position for good aerodynamics.<ref name="richardson39"/>