Editing Procellariiformes (section)

===Breeding behaviour===
{{see also|Seabird breeding behavior|l1=Seabird breeding behaviour}}

====Breeding colonies====
[[File:Xmas shearwaters roosting.jpg|thumb|220px|[[Christmas shearwater]]s are one of the surface-nesting tropical procellariiforms.]]
All procellariiforms are colonial, predominantly breeding on offshore or oceanic islands. The few species that nest on continents do so in inhospitable environments such as dry deserts or on Antarctica. These colonies can vary from the widely spaced colonies of the giant petrels to the dense 3.6 million-strong colonies of [[Leach's storm petrel]]s.<ref name=j3/> For almost all species the need to breed is the only reason that procellariiforms return to land at all. Some of the larger petrels have to nest on windswept locations as they require wind to take off and forage for food.<ref name="Double" /> Within the colonies, pairs defend usually small [[Territory (animal)|territories]] (the giant petrels and some albatrosses can have very large territories) which is the small area around either the nest or a burrow. Competition between pairs can be intense, as is competition between species, particularly for burrows. Larger species of petrels will even kill the chicks and even adults of smaller species in disputes over burrows.<ref name ="Medeiros"/> Burrows and natural crevices are most commonly used by the smaller species; all the storm petrels and [[diving petrel]]s are cavity nesters, as are many of the [[procellariid]]s. The fulmarine petrels and some tropical [[gadfly petrel]]s and [[shearwater]]s are surface nesters, as are all the albatrosses.<ref>{{cite book |title=Chemical Signals in Vertebrates 10 | publisher=Springer |author1=Cunningham, G.B. |author2=Nevitt, G.A. |year=2005 |pages=403 |editor1=Mason, R.T. |editor2=Lemaster, Michael P. |editor3=Müller-Schwarze, D. | chapter=The Sense of Smell in Procellariiformes |chapter-url=https://books.google.com/books?id=zBZZNiN9_PoC&pg=PA403|isbn=9780387251592 }}</ref>

Procellariiforms show high levels of [[philopatry]], both site fidelity and natal philopatry. Natal philopatry is the tendency of an individual bird to return to its natal colony to breed, often many years after leaving the colony as a chick. This tendency has been shown through [[bird ringing|ringing studies]] and [[mitochondrial DNA]] studies. Birds ringed as chicks have been recaptured close to their original nests, sometimes extremely close; in the Laysan albatross the average distance between hatching site and the site where a bird established its own territory was {{convert|22|m|ft|abbr=on}},<ref>{{cite journal |last1=Fisher |first1=H. I. |year=1976 |title=Some dynamics of a breeding colony of Laysan Albatrosses |url=http://sora.unm.edu/node/129258 |journal=Wilson Bulletin |volume=88 |pages=121–142}}</ref> and a study of [[Cory's shearwater]]s nesting near [[Corsica]] found that nine out of 61 male chicks that returned to breed at their natal colony actually bred in the burrow they were raised in.<ref name=j4/> Mitochondrial DNA provides evidence of restricted [[gene flow]] between different colonies, strongly suggesting philopatry.<ref name=j5/>

The other type of philopatry exhibited is site fidelity, where pairs of birds return to the same nesting site for a number of years. Among the most extreme examples known of this tendency was the fidelity of a ringed northern fulmar that returned to the same nest site for 25 years. The average number of birds returning to the same nest sites is high in all species studied, with around 91 percent for [[Bulwer's petrel]]s,<ref name=j6/> and 85 percent of males and 76 percent of females for Cory's shearwaters (after a successful breeding attempt).<ref>{{cite journal |doi=10.1080/00063659409477193 |last1=Thibault |first1=J.-C. |year=1994 |title=Nest-site tenacity and mate fidelity in relation to breeding success in Cory's Shearwater ''Calonectris diomedea'' |journal=Bird Study |volume=41 |issue=1 |pages=25–28|bibcode=1994BirdS..41...25T }}</ref>

====Pair bonds and life history====
[[File:Kerguelen - Diomedea exulans - wooing.jpg|thumb|alt= Three massive birds stand on low grasslands, the closest bird has its long wings outstretched and its head pointing upward|left|[[Wandering albatross]]es performing their mating dances on the [[Kerguelen Islands]]]]
Procellariiforms are [[monogamy in animals|monogamous]] breeders and form long-term pair bonds. These pair bonds take several years to develop in some species, particularly with the albatrosses. Once formed, they last for many breeding seasons, in some cases for the life of the pair. Petrel courtship can be elaborate. It reaches its extreme with the albatrosses, where pairs spend many years perfecting and elaborating mating dances.<ref>{{cite journal |doi=10.1163/156853981X00257 |last1=Jouventin |first1=P. |last2=de Monicault |first2=G. |last3=Blosseville |first3=J.M. |year=1981 |title=La danse de l'albatros, ''Phoebetria fusca'' |journal=Behaviour |volume=78 |issue=1–2 |pages=43–80 |language=fr}}</ref> These dances are composed of synchronised performances of various actions such as [[preening]], pointing, calling, bill clacking, staring, and combinations of such behaviours (like the sky-call).<ref name=j7/> Each particular pair will develop their own individual version of the dance. The breeding behaviour of other procellariiforms is less elaborate, although similar bonding behaviours are involved, particularly for surface-nesting species. These can involve synchronised flights, mutual preening and [[Birdsong|calling]]. Calls are important for helping birds locate potential mates and distinguishing between species, and may also help individuals assess the quality of potential mates.<ref>{{cite journal |doi=10.1080/08927014.1994.9522988 |last1=Genevois |first1=F. |last2=Bretagnolle |first2=V. |year=1994 |title=Male Blue Petrels reveal their body mass when calling |journal=Ethology Ecology & Evolution |volume=6 |issue=3 |pages=377–383|bibcode=1994EtEcE...6..377G }}</ref> After pairs have been formed, calls serve to help them reunite; the ability of individuals to recognise their own mate has been demonstrated in several species.<ref>{{cite thesis |url= https://cdr.lib.unc.edu/concern/dissertations/cc08hg50x |title=Acoustic communication in colonial seabirds: individual, sexual, and species-specific variation in acoustic signals of Pterodroma petrels |publisher=University of North Carolina at Chapel Hill |degree=PhD |year=2008 |author=McKown, Matthew W. |pages=90–91 |access-date=31 August 2024}}</ref>

Procellariiforms are [[k-selection|K-selected]], being long-lived and caring extensively for their few offspring. Breeding is delayed for several years after [[fledge|fledging]], sometimes for as long as ten years in the largest species. Once they begin breeding, they make only a single breeding attempt per nesting season; even if the egg is lost early in the season, they seldom re-lay. Much effort is placed into laying a single (proportionally) large [[egg (biology)|egg]] and raising a single chick. Procellariiforms are long-lived: the longest living albatross known survived for 51 years, but was probably older,<ref>{{cite journal |doi=10.1071/MU9930269 |last1=Robertson |first1=C.J.R. |year=1993 |title=Survival and longevity of the Northern Royal Albatross ''Diomedea epomophora sanfordi'' at Taiaroa Head" 1937–93 |journal=Emu |volume=93 |issue=4 |pages=269–276|bibcode=1993EmuAO..93..269R }}</ref> and even the tiny storm-petrels are known to have survived for 30 years.<ref>Klimkiewicz, M. K. 2007. [http://www.pwrc.usgs.gov/BBL/homepage/longvrec.htm Longevity Records of North American Birds] {{webarchive|url=https://web.archive.org/web/20110519022957/http://www.pwrc.usgs.gov/BBL/homepage/longvrec.htm |date=2011-05-19 }}. Version 2007.1. Patuxent Wildlife Research Center. Bird Banding Laboratory. Laurel MD.</ref> Additionally, the oldest living bird is [[Wisdom (albatross)|Wisdom]], a female Laysan albatross.

====Nesting and chick rearing====
[[File:W-tail with chick.jpg|thumb|A semi-precocial [[wedge-tailed shearwater]] chick with guarding parent]]
The majority of procellariiforms nest once a year and do so seasonally.<ref>Brooke, 2004. p. 46</ref> Some tropical shearwaters, like the [[Christmas shearwater]], are able to nest on cycles slightly shorter than a year, and the large [[great albatross]]es (genus ''[[Diomedea]]'') nest in alternate years (if successful). Most temperate and polar species nest over the spring-summer, although some albatrosses and procellariids nest over the winter. In the tropics, some species can be found breeding throughout the year, but most nest in discreet periods. Procellariiforms return to nesting colonies as much as several months before laying, and attend their nest sites regularly before copulation. Prior to laying, females embark on a lengthy pre-laying exodus to build up energy reserves in order to lay the exceptionally large egg. In the stormy petrel{{clarification|reason= Which species of storm petrel?|date=October 2023}}, a very small procellariiform, the egg can be 29 percent of the body weight of the female, while in the grey-faced petrel, the female may spend as much as 80 days feeding out at sea after courtship before laying the egg.<ref name=Teara2>{{cite web |url=http://www.teara.govt.nz/en/petrels/page-1 | title=Petrels: Breeding |publisher=Teara: The Encyclopedia of New Zealand |date=13 July 2012 |access-date=2 March 2013 |author=Wilson, Kerry-Jayne |pages=2}}</ref>

When the female returns and lays, incubation is shared between the sexes, with the male taking the first [[avian incubation|incubation]] stint and the female returning to sea. The duration of individual stints varies from just a few days to as much as several weeks, during which the incubating bird can lose a considerable amount of weight.<ref>Warham, J. (1990) ''The Petrels – Their Ecology and Breeding Systems'' London: Academic Press. {{ISBN|978-0-12-735420-0}}</ref> The incubation period varies from species to species, around 40 days for the smallest storm-petrels but longer for the largest species; for albatrosses it can span 70 to 80 days, which is the longest incubation period of any bird.<ref>Brooke, 2004. p. 67</ref>
[[File:Feeding chick.JPG|thumb|left|A [[Laysan albatross]] feeds its chick. The parent pumps food from a modified foregut, the proventriculus, and the chick catches the meal in its lower mandible.]]

Upon hatching, the chicks are semi-[[precocial]], having open eyes, a dense covering of white or grey [[down feather]]s, and the ability to move around the nesting site. After hatching, the incubating adult remains with the chick for a number of days, a period known as the guard phase. In the case of most burrow-nesting species, this is only until the chick is able to [[thermoregulation|thermoregulate]], usually two or three days. Diving-petrel chicks take longer to thermoregulate and have a longer guard phase than other burrow nesters. However, surface-nesting species, which have to deal with a greater range of weather and to contend with predators like [[skua]]s and [[frigatebird]]s, consequently have a longer guard phase (as long as two weeks in procellariids and three weeks in albatrosses).<ref>Brooke, 2004. p. 75</ref>

The chick is fed by both parents. Chicks are fed on fish, squid, krill, and [[stomach oil]]. Stomach oil is [[oil]] composed of neutral dietary [[lipid]]s that are the residue created by [[digestion]] of the prey items. As an energy source for chicks it has several advantages over undigested prey, its [[calorie|calorific]] value is around 9.6 kcal per gram, which is only slightly lower than the value for [[Diesel fuel|diesel]] oil.<ref name = "stomach"/> This can be a real advantage for species that range over huge distances to provide food for hungry chicks.<ref name=j8/> The oil is also used in defence. All procellariiforms create stomach oil except the diving-petrels.<ref name = "stomach"/>

The chick fledges between two and nine months after hatching, almost twice as long as a gull of the same body mass. The reasons behind the length of time are associated with the distance from the breeding site to food. First, there are few predators at the nesting colonies, therefore there is no pressure to fledge quickly.  Second, the time between feedings is long due to the distance from the nest site that adults forage, thus a chick that had a higher growth rate would stand a better chance of starving to death.<ref name="Double" /> The duration between feedings vary among species and during the stages of development. Small feeds are frequent during the guard phase, but afterward become less frequent. However, each feed can deliver a large amount of energy; both sooty shearwater and mottled petrel chicks have been recorded to double their weight in a single night, probably when fed by both parents.<ref name=Teara2/>