Editing Procellariiformes (section)

==Biology==
===Distribution and movements===
{{See also|List of Procellariiformes by population}}
The procellariiforms have a [[cosmopolitan distribution]] across the world's oceans and seas, although at the levels of family and genus there are some clear patterns. [[Antarctic petrel]]s, ''Thalassoica antarctica'', have to fly over {{convert|100|mi|km|abbr=on}} to get to the ocean from their breeding colonies in [[Antarctica]], and [[northern fulmar]]s breed on the northeastern tip of [[Greenland]], the northernmost piece of [[land]].<ref name="Double">{{cite encyclopedia |last=Double |first=D.C. |editor1-first=Michael |editor1-last= Hutchins |encyclopedia=Grzimek's Animal Life Encyclopedia |title=Procellariiformes |edition=2 |year=2003 |publisher=Gale Group |volume=8 Birds I Tinamous and Ratites to Hoatzins |location=Farmington Hills, MI |isbn=978-0-7876-5784-0 |pages=107–110}}</ref> The most cosmopolitan family is the [[Procellariidae]], which are found in tropical, temperate and polar zones of both the Northern and the Southern Hemispheres, though the majority do not breed in the tropics, and half the species are restricted to southern temperate and polar regions.<ref>{{cite book | url=https://archive.org/stream/worldatlasofbiod02groo#page/128/mode/2up | title=World Atlas of Biodiversity: earth's living resources in the 21st century | publisher=University of California Press | year=2002 | access-date=2 March 2013 |author1=Groombridge, Brian |author2=Jenkins, Martin D | pages=128&ndash;129 (Table 6.7)| isbn=9780520236684 }}</ref> The gadfly petrels, ''[[Pterodroma]]'', have a generally [[tropical]] and [[temperate]] distribution, whereas the [[fulmarine petrel]]s are mostly [[polar region|polar]] with some temperate species. The majority of the fulmarine petrels, along with the [[prion (bird)|prions]], are confined to the Southern Hemisphere.<ref name=Teara>{{cite web |url=http://www.teara.govt.nz/en/petrels/page-1 |title=Petrels | publisher=Teara: The Encyclopedia of New Zealand |date=13 July 2012 |access-date=2 March 2013 |author=Wilson, Kerry-Jayne | pages=1–5}}</ref>

The [[storm petrel]]s are almost as widespread as the procellariids, and fall into two distinct families; the [[Oceanitidae]] have a mostly Southern Hemisphere distribution and the [[Hydrobatidae]] are found mostly in the Northern Hemisphere. Amongst the [[albatross]]es the majority of the family is restricted to the Southern Hemisphere, feeding and nesting in cool temperate areas, although one genus, ''[[Phoebastria]]'', ranges across the north Pacific. The family is absent from the north Atlantic, although fossil records indicate they bred there once.<ref name = "olson">{{cite journal |doi=10.1073/pnas.1934576100 |last1=Olson |first1=S.L. |last2=Hearty |first2=P.J. |year=2003 |title=Probable extirpation of a breeding colony of Short-tailed Albatross (''Phoebastria albatrus'') on Bermuda by Pleistocene sea-level rise |journal=Proceedings of the National Academy of Sciences |volume=100 |issue=22 |pages=12825–12829 |pmid=14566060 |pmc=240703|bibcode=2003PNAS..10012825O |doi-access=free }}</ref> Finally the [[diving petrel]]s are restricted to the Southern Hemisphere.<ref>{{cite web |url=http://animaldiversity.ummz.umich.edu/accounts/Pelecanoididae/ |title=Pelecanoididae diving petrels |publisher=University of Michigan Museum of Zoology |year=2012 |access-date=2 March 2013 |author=Cholewiak, Danielle}}</ref>

====Migration====

The various species within the order have a variety of [[bird migration|migration]] strategies. Some species undertake regular trans-equatorial migrations, such as the [[sooty shearwater]] which annually migrates from its breeding grounds in New Zealand and Chile to the North Pacific off [[Japan]], [[Alaska]] and California, an annual round trip of {{convert|64000|km|mi|abbr=on}}, the second longest measured annual migration of any bird.<ref>{{cite journal |doi=10.1073/pnas.0603715103 |last1=Shaffer |first1=S.A. |last2=Tremblay |first2=Y. |last3=Weimerskirch |first3= H. |last4=Scott |first4=D. |last5=Thompson |first5=D.R. |last6=Sagar |first6=P.M. |last7=Moller |first7=H. |last8=Taylor |first8=G.A. |last9=Foley |first9=D.G. |last10=Block |first10=B.A. | first11=Costa |last11=D.P. |year=2006 |title=Migratory shearwaters integrate oceanic resources across the Pacific Ocean in an endless summer |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=103 |issue=34 |pages=12799–12802 |pmid=16908846 |pmc=1568927  |bibcode=2006PNAS..10312799S |doi-access=free }}</ref> A number of other petrel species undertake trans-equatorial migrations, including the [[Wilson's storm petrel]] and the [[Providence petrel]], but no albatrosses cross the equator, as they rely on wind assisted flight. There are other long-distance migrants within the order; [[Swinhoe's storm petrel]]s breed in the western Pacific and migrate to the western Indian Ocean,<ref>{{cite journal |last1=Van Den |first1=Berg A.B. |last2=Smeenk |first2=C. |last3=Bosman |first3=C.A.W. |last4=Haase |first4=B.J.M. |last5=Van Der |first5=Niet A.M. |last6=Cadée |first6=G.C. |year=1990 |title=Barau's petrel ''Pterodroma baraui'', Jouanin's petrel ''Bulweria fallax'' and other seabirds in the northern Indian Ocean in June–July 1984 and 1985 |journal=Ardea |volume=79 |pages=1–14 |url=http://ardea.nou.nu/ardea_search3.php?key=nummer&keyin=79&k2=1 }}</ref> and [[Bonin petrel]]s nesting in [[Hawaii]] migrate to the coast of Japan during the non-breeding season.<ref>{{cite book |author1=Seto, N. W. H. |author2=O'Daniel, D. |year=1999 |chapter=Bonin Petrel (''Pterodroma hypoleuca'') |title=The Birds of North America, No. 385 |editor=Poole A. |editor2=Gill, F |publisher=The Birds of North America |location=Philadelphia, PA}}</ref>

====Navigation====

Many species in the order travel long distances over open water but return to the same nest site each year, raising the question of how they navigate so accurately.<ref name=Lockley>{{cite book |last=Lockley |first=Ronald M. |title=Animal Navigation |year=1967 |publisher=Pan Books| pages=114–117}}</ref> The Welsh naturalist [[Ronald Lockley]] carried out early research into [[animal navigation]] with the [[Manx shearwater]]s that nested on the island of [[Skokholm]]. In release experiments, a Manx shearwater flew from [[Boston]] to Skokholm, a distance of {{convert|3000|mi|km|abbr=off}} in 12{{frac|1|2}} days.<ref name=Lockley/><ref name=BirdsBritManx>Cocker, 2005. pp. 21–24</ref>
Lockley showed that when released "under a clear sky" with sun or stars visible, the shearwaters  oriented themselves and then "flew off in a direct line for Skokholm", making the journey so rapidly that they must have flown almost in a straight line. But if the sky was overcast at the time of release, the shearwaters flew around in circles "as if lost" and returned slowly or not at all, implying that they navigated using astronomical cues.<ref name=Lockley/>

Researchers have also begun investigating olfaction's role in procellariiform navigation. In a study where Cory's shearwaters were rendered anosmic with zinc sulphate, a compound which kills the surface layer of the olfactory epithelium, and released hundreds of kilometers away from their home colony at night, control birds found their way to their home nests before night was over, whereas anosmic birds did not home until the next day.<ref>{{Cite journal|last1=Dell'Ariccia|first1=G.|last2=Bonadonna|first2=F.|date=2013-04-15|title=Back home at night or out until morning? Nycthemeral variations in homing of anosmic Cory's shearwaters in a diurnal colony|journal=Journal of Experimental Biology|language=en|volume=216|issue=8|pages=1430–1433|doi=10.1242/jeb.082826|pmid=23307801|issn=0022-0949|doi-access=free}}</ref> A similar study that released Cory's shearwaters 800&nbsp;km from their home nests, testing both magnetic and olfactory disturbances’ effects on navigation, found that anosmic birds took longer to home than magnetically disturbed or control birds.<ref>{{Cite journal|last1=Gagliardo|first1=A.|last2=Bried|first2=J.|last3=Lambardi|first3=P.|last4=Luschi|first4=P.|last5=Wikelski|first5=M.|last6=Bonadonna|first6=F.|date=2013-08-01|title=Oceanic navigation in Cory's shearwaters: evidence for a crucial role of olfactory cues for homing after displacement|journal=Journal of Experimental Biology|language=en|volume=216|issue=15|pages=2798–2805|doi=10.1242/jeb.085738|pmid=23842626|issn=0022-0949|doi-access=free|hdl=11568/208687|hdl-access=free}}</ref>

===Morphology and flight===
[[File:070226 southern royal albatross off Kaikoura 2.jpg|alt= massive white bird with black wings and pink bill sits on the surface of the water|thumb|left|The [[southern royal albatross]] is one of the largest of the Procellariiformes.]]
Procellariiforms range in size from the very large [[wandering albatross]], at {{convert|11|kg|lb|abbr=on}} and a {{convert|3.6|m|ft|abbr=off|adj=on}} wingspan, to tiny birds like the [[least storm petrel]], at {{convert|20|g|oz|abbr=on}} with a {{convert|32|cm|in|abbr=off|adj=on}} wingspan,<ref name="Double" /> and the smallest of the prions, the [[fairy prion]], with a wingspan of {{convert|23|to|28|cm|in|abbr=on}}.<ref name="Maynard">{{cite encyclopedia |last=Maynard |first=B. J.|editor1-first=Michael |editor1-last= Hutchins|encyclopedia=Grzimek's Animal Life Encyclopedia |title=Shearwaters, petrels, and fulmars (procellariidae) |edition=2 |year=2003 |publisher=Gale Group|volume=8 Birds I Tinamous and Ratites to Hoatzins |pages=123–127 |isbn=978-0-7876-5784-0}}</ref> Their nostrils are enclosed in one or two tubes on their straight deeply-grooved bills with hooked tips. The beaks are made up of several plates. Their wings are long and narrow; the feet are webbed, and the hind toe is undeveloped or non-existent; their adult [[plumage]] is predominantly black, white, and grey.<ref>{{cite journal |title=Adaptive significance of seabird coloration: The case of Procellariiforms |author=Bretagnolle, Vincent |journal=The American Naturalist |year=1993 |volume=142 |issue=1 |pages=141–173 |jstor=2462637|pmid=19425973 |doi=10.1086/285532 |s2cid=205983145 }}</ref>

The order has a few unifying characteristics, starting with their tubular nasal passage which is used for [[olfaction]].<ref name=j1/> Procellariiformes that nest in burrows have a strong sense of smell, being able to detect [[dimethyl sulfide]] released from [[plankton]] in the ocean.<ref>{{Cite journal|last1=Buskirk|first1=R. W. Van|last2=Nevitt|first2=G. A.|date=2008|title=The influence of developmental environment on the evolution of olfactory foraging behaviour in procellariiform seabirds|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1420-9101.2007.01465.x|journal=Journal of Evolutionary Biology|language=en|volume=21|issue=1|pages=67–76|doi=10.1111/j.1420-9101.2007.01465.x|pmid=18021198|s2cid=30270085|issn=1420-9101|url-access=subscription}}</ref> This ability to smell helps to locate patchily distributed prey at sea and may also help locate their nests within [[seabird colony|nesting colonies]].<ref>{{cite journal |last1=Bonadonna |first1=Francesco |last2=Cunningham |first2=Gregory B. |last3=Jouventin |first3=Pierre |last4=Hesters |first4=Florence |last5=Nevitt |first5=Gabrielle A. |year=2003 |title=Evidence for nest-odour recognition in two species of diving petrel |journal=Journal of Experimental Biology |volume=206 |issue=Pt 20 |pages=3719–3722 |doi=10.1242/jeb.00610 |pmid=12966063|doi-access=free }}</ref> In contrast, surface nesting Procellariiformes have increased vision, having six times better [[spatial resolution]] than those that nest in burrows.<ref>{{Cite journal|last1=Mitkus|first1=Mindaugas|last2=Nevitt|first2=Gabrielle A.|last3=Danielsen|first3=Johannis|last4=Kelber|first4=Almut|date=2016-11-01|title=Vision on the high seas: spatial resolution and optical sensitivity in two procellariiform seabirds with different foraging strategies|url=https://jeb.biologists.org/content/219/21/3329|journal=Journal of Experimental Biology|language=en|volume=219|issue=21|pages=3329–3338|doi=10.1242/jeb.140905|issn=0022-0949|pmid=27591308|doi-access=free}}</ref> The structure of the [[Beak|bill]], which contains seven to nine distinct horny plates, is another unifying feature, although there are differences within the order. Petrels have a plate called the maxillary unguis that forms a hook on the maxilla. The smaller members of the order have a comb-like mandible, made by the [[tomia]]l plate, for [[plankton]] feeding. Most members of the order are unable to walk well on land, and many species visit their remote breeding islands only at night. The exceptions are the huge albatrosses, several of the gadfly petrels and shearwaters and the fulmar-petrels. The latter can disable even large predatory birds with their obnoxious [[stomach oil]], which they can project some distance. This stomach oil, stored in the [[proventriculus]], is a digestive residue created in the [[foregut]] of all tubenoses except the diving petrels, and is used mainly for storage of energy-rich food during their long flights.<ref>{{cite journal |url=http://www.marineornithology.org/PDF/31_2/31_2_101-112.pdf |title=Biogeography of Procellariiform foraging strategies: does ocean productivity influence provisioning? |author1=Baduini, Cheryl L. |author2=Hyrenbach, K. David |journal=Marine Ornithology |year=2003 |volume=31 |issue=2 |pages=101–112|doi=10.5038/2074-1235.31.2.570 }}</ref> The oil is also fed to their young, as well as being used for defense.<ref name="Double"/><ref>{{cite book |url=https://books.google.com/books?id=qrI5ph6BWiIC&pg=PA149 |title=A Wildlife Guide to Chile: Continental Chile, Chilean Antarctica, Easter Island, Juan Fernandez Archipelago |publisher=Princeton University Press |author=Chester, Sharon |year=2010 |page=149 |isbn=9780691129761}}</ref>

[[File:Whitefacedstormpetrel1.jpg|thumb|alt= White bird with grey upperparts and black face mask jumps off water surface with elongated legs.|The [[white-faced storm petrel]] moves across the water's surface in a series of bounding leaps.]]
Procellariiforms drink seawater, so they have to excrete excess salt.  All birds have an enlarged nasal gland at the base of the bill, above the eyes, and in the Procellariiformes the gland is active. In general terms, the salt gland removes salt from the system and forms a 5 percent saline solution that drips out of the nostrils, or is forcibly ejected in some petrels.<ref>{{Cite book |last1=Ehrlich |first1=Paul R. |last2=Dobkin |first2=David, S. |last3=Wheye |first3=Darryl |title=The Birders Handbook |edition=First |year=1988 |publisher=Simon & Schuster |location=New York, NY |isbn=978-0-671-65989-9 |pages=29–31 |url-access=registration |url=https://archive.org/details/birdershandbookf00ehrl_0 }}</ref> The processes behind this involve high levels of [[sodium]] ion reabsorption into the [[blood plasma]] within the kidneys, and secretion of [[sodium chloride]] via the [[salt gland]]s using less water than was absorbed, which essentially generates salt-free water for other physiological uses. This high efficiency of sodium ion absorption is attributed to mammalian-type [[nephrons]].<ref>{{cite journal |last=Hughes |first=M.R. |title=Regulation of salt gland, gut and kidney interactions |journal=Comparative Biochemistry and Physiology A |year=2003 |volume=136 |issue=3 |doi=10.1016/j.cbpb.2003.09.005 |pmid=14613781 |pages=507–524}}</ref>

Most albatrosses and procellariids use two techniques to minimise exertion while flying, namely, [[dynamic soaring]] and [[slope soaring]]. The albatrosses and [[giant petrel]]s share a morphological adaptation to aid in flight, a sheet of [[tendon]] which locks the wing when fully extended, allowing the wing to be kept up and out without any muscle effort.<ref name ="pen">{{cite journal |doi=10.1098/rstb.1982.0158 |last1=Pennycuick |first1= C.J. |year=1982 |title=The flight of petrels and albatrosses (Procellariiformes), observed in South Georgia and its vicinity |journal =Philosophical Transactions of the Royal Society of London B |volume=300 |issue=1098 |pages=75–106 |bibcode=1982RSPTB.300...75P |doi-access= }}</ref> Amongst the Oceanitinae storm-petrels there are two unique flight patterns, one being surface pattering. In this they move across the water surface holding and moving their feet on the water's surface while holding steady above the water, and remaining stationary by hovering with rapid fluttering or by using the wind to anchor themselves in place.<ref name = "Withers"/> A similar flight method is thought to have been used by the extinct petrel family [[Diomedeoididae]].<ref name ="Mayr"/> The [[white-faced storm petrel]] possesses a unique variation on pattering: holding its wings motionless and at an angle into the wind, it pushes itself off the water's surface in a succession of bounding jumps.<ref name=j2/>

===Diet and feeding===
The procellariiforms are for the most part exclusively marine [[foraging|foragers]]; the only exception to this rule are the two species of giant petrel, which regularly feed on [[carrion]] or other seabirds while on land. While some other species of fulmarine and ''[[Procellaria]]'' petrels also take carrion, the diet of most species of albatrosses and petrels is dominated by fish, squid, krill and other marine zooplankton. The importance of these food sources varies from species to species and family to family. For example, of the two albatross species found in Hawaii, the [[black-footed albatross]] takes mostly fish, while the [[Laysan albatross|Laysan]] feeds mainly on squid.<ref>Brooke, 2004. p. 126</ref> The albatrosses in general feed on fish, squid and krill. Among the procellariids, the prions concentrate on small crustacea, the fulmarine petrels take fish and krill but little squid, while the ''Procellaria'' petrels consume mainly squid.  The storm petrels take small droplets of oil from the surface of the water,<ref>{{cite book |title=Birds of Venezuela |publisher=Princeton University Press |author=Hilty, Steven L. |year=2002 |page=188 |isbn=978-0691092508}}</ref> as well as small crustaceans and fish.<ref>Brooke, 2004. p. 127</ref>

Petrels obtain food by snatching prey while swimming on the surface, snatching prey from the wing or diving down under the water to pursue prey. Dipping down from flight is most commonly used by the [[gadfly petrel]]s and the [[storm petrel]]s. There have been records of [[wedge-tailed shearwater]]s snatching [[flying fish]] from the air, but as a rule this technique is rare. Some diving birds may aid diving by beginning with a plunge from the air, but for the most part petrels are active divers and use their wings to move around under the water. The depths achieved by various species were determined in the 1990s and came as a surprise to scientists; [[short-tailed shearwater]]s have been recorded diving to {{convert|70|m|abbr=on}} and the [[Light-mantled sooty albatross]] to {{convert|12|m|abbr=on}}.<ref>Brooke, 2004. pp. 128–131</ref>

===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/>