Editing Seabird (section)

== Characteristics ==

=== Adaptations to life at sea ===
Seabirds have made numerous adaptations to living on and feeding in the sea. [[Wing]] morphology has been shaped by the [[ecological niche|niche]] an individual species or family has [[evolution|evolved]], so that looking at a wing's shape and [[wing loading|loading]] can tell a scientist about its life feeding behaviour. Longer wings and low wing loading are typical of more [[pelagic]] species, while diving species have shorter wings.<ref name="Gaston">Gaston, Anthony J. (2004). ''Seabirds: A Natural History'' New Haven:Yale University Press, {{ISBN|0-300-10406-5}}</ref> Species such as the [[wandering albatross]], which forage over huge areas of sea, have a reduced capacity for powered flight and are dependent on a type of [[Gliding flight|gliding]] called [[dynamic soaring]] (where the wind deflected by waves provides lift) as well as slope soaring.<ref>{{cite journal|author=Pennycuick, 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 B]] |volume=300|pages=75–106|doi=10.1098/rstb.1982.0158|issue=1098|bibcode=1982RSPTB.300...75P|doi-access=free}}</ref> Seabirds also almost always have [[Bird feet and legs#Webbing and lobation|webbed feet]], to aid movement on the surface as well as assisting diving in some species. The [[Procellariiformes]] are unusual among birds in having a strong [[olfaction|sense of smell]], which is used to find widely distributed food in a vast ocean,<ref>{{cite journal|author1=Lequette, B. |author2=Verheyden, C. |author3=Jowentin, P. |year=1989|title=Olfaction in Subantarctic seabirds: Its phylogenetic and ecological significance|journal=The Condor |volume=91|pages=732–735|url=http://sora.unm.edu/sites/default/files/journals/condor/v091n03/p0732-p0735.pdf|doi=10.2307/1368131|issue=3|jstor=1368131 }}</ref> and help distinguish familiar nest odours from unfamiliar ones.<ref>{{cite journal|last1=Mitkus|first1=Mindaugas|last2=Nevitt|first2=Gabrielle A.|last3=Kelber|first3=Almut|date=2018|title=Development of the Visual System in a Burrow-Nesting Seabird: Leach's Storm Petrel|url=https://doi.org/10.1159/000484080|journal=Brain, Behavior and Evolution|language=en|volume=91|issue=1|pages=4–16|doi=10.1159/000484080|pmid=29212065|s2cid=4964467|issn=0006-8977|access-date=March 15, 2021|via=Karger|url-access=subscription}}</ref>

[[File:Phalacrocorax-auritus-007.jpg|thumb|left|Cormorants, like this [[double-crested cormorant]], have plumage that is partly wettable. This functional adaptation balances the competing requirement for [[thermoregulation]] against that of the need to reduce buoyancy.<ref name=JAB2005>{{cite journal|author1=Grémillet, D. |author2=Chauvin, C. |author3=Wilson, R. P. |author4=Le Maho, Y. |author5=Wanless, S. |year=2005|title= Unusual feather structure allows partial plumage wettability in diving great cormorants ''Phalacrocorax carbo''|journal=Journal of Avian Biology |volume=36 |issue=1 |pages= 57–63|doi=10.1111/j.0908-8857.2005.03331.x}}</ref>]]

[[Supraorbital gland|Salt glands]] are used by seabirds to deal with the [[Edible salt|salt]] they ingest by drinking and feeding (particularly on [[crustacean]]s), and to help them [[osmoregulation|osmoregulate]].<ref name="Harrison">Harrison, C. S. (1990) ''Seabirds of Hawaii, Natural History and Conservation'' Ithaca:Cornell University Press, {{ISBN|0-8014-2449-6}}</ref> The [[excretion]]s from these glands (which are positioned in the head of the birds, emerging from the [[nasal cavity]]) are almost pure [[sodium chloride]].<ref name="Schmidt-Nielson">{{cite journal |last1=Schmidt-Nielson|first1=Knut |date=May 1960 |title= The Salt-Secreting Gland of Marine Birds |journal=Circulation |volume=21 |issue=5 |pages=955–967 |doi= 10.1161/01.CIR.21.5.955 |pmid=14443123 |doi-access=free }}</ref>

With the exception of the [[cormorant]]s and some terns, and in common with most other birds, all seabirds have waterproof [[plumage]]. However, compared to land birds, they have far more feathers protecting their bodies. This dense plumage is better able to protect the bird from getting wet, and cold is kept out by a dense layer of [[down feather]]s. The cormorants possess a layer of unique feathers that retain a smaller layer of air (compared to other diving birds) but otherwise soak up water.<ref name=JAB2005/> This allows them to swim without fighting the [[buoyancy]] that retaining air in the feathers causes, yet retain enough air to prevent the bird losing excessive heat through contact with water.<ref name="King233">{{cite book |last=King |first=Richard J. |date=2013 |title=The Devil's Cormorant: A Natural History |location=Durham, NH |publisher=University of New Hampshire Press |page=233 |isbn=978-1-61168-699-9}}</ref>

The plumage of most seabirds is less colourful than that of land birds, restricted in the main to variations of black, white or grey.<ref name="Gaston" /> A few species sport colourful plumes (such as the tropicbirds and some penguins), but most of the colour in seabirds appears in the bills and legs. The plumage of seabirds is thought in many cases to be for [[camouflage]], both defensive (the colour of [[United States Navy|US Navy]] [[battleship]]s is the same as that of [[Antarctic prion]]s,<ref name="Gaston" /> and in both cases it reduces visibility at sea) and aggressive (the white underside possessed by many seabirds helps hide them from prey below). The usually black wing tips help prevent wear, as they contain melanins that help the feathers resist abrasion.<ref name="Elphick2016">{{cite book|last=Elphick|first=Jonathan|year=2016|publisher=Firefly Books|title=Birds: A Complete Guide to their Biology and Behavior|location=Buffalo, New York|isbn=978-1-77085-762-9|page=80}}</ref>

=== Diet and feeding ===
Seabirds evolved to exploit different food resources in the world's seas and oceans, and to a great extent, their [[physiology]] and [[ethology|behaviour]] have been shaped by their [[diet (nutrition)|diet]]. These evolutionary forces have often caused species in different families and even orders to evolve similar strategies and adaptations to the same problems, leading to remarkable [[convergent evolution]], such as that between auks and penguins. There are four basic feeding strategies, or ecological guilds, for feeding at sea: surface feeding, pursuit diving, plunge diving, and predation of [[higher vertebrates]]; within these guilds, there are multiple variations on the theme.<ref name="Castro">{{cite book |last1=Castro|first1=Peter|last2=Huber|first2=Michael E.|date=2003|title=Marine Biology|location=University of Michigan|publisher=McGraw-Hill|page=186|isbn=0070294216}}</ref>

==== Surface feeding ====
Many seabirds feed on the ocean's surface, as the action of marine [[ocean current|currents]] often concentrates food such as [[krill]], [[forage fish]], [[squid]], or other prey items within reach of a dipped head.

[[File:Wilson's storm petrel.jpg|thumb|left|[[Wilson's storm petrel]]s pattering on the water's surface]]

Surface feeding itself can be broken up into two different approaches, surface feeding while [[bird flight|flying]] (for example as practiced by [[gadfly petrel]]s, [[frigatebird]]s, and [[storm petrel]]s), and surface feeding while swimming (examples of which are practiced by [[gull]]s, [[fulmar]]s, many of the [[shearwater]]s and gadfly petrels). Surface feeders in flight include some of the most acrobatic of seabirds, which either snatch morsels from the water (as do frigatebirds and some terns), or "walk", pattering and hovering on the water's surface, as some of the storm petrels do.<ref>{{cite journal|author=Withers, P. C. |year=1979|title=Aerodynamics and hydrodynamics of the 'hovering' flight of Wilson's storm petrel |journal=Journal of Experimental Biology |volume=80|pages= 83–91 |doi=10.1242/jeb.80.1.83|url=http://jeb.biologists.org/cgi/reprint/80/1/83|doi-access=free|url-access=subscription}}</ref> Many of these do not ever land in the water, and some, such as the frigatebirds, have difficulty getting airborne again should they do so.<ref>Metz, V. G. and Schreiber, E. A. (2002). Great Frigatebird (''Fregata minor''). In ''The Birds of North America'', No. '''681''' (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA</ref> Another seabird family that does not land while feeding is the [[Skimmer (bird)|skimmer]], which has a unique fishing method: flying along the surface with the lower mandible in the water—this shuts automatically when the bill touches something in the water. The skimmer's bill reflects its unusual lifestyle, with the lower mandible uniquely being longer than the upper one.<ref name = "HBW">{{Citation | first = R. L. | last = Zusi |editor-first = Josep | editor-last = del Hoyo | editor2-first = Andrew | editor2-last = Elliott | editor3-last = Sargatal | editor3-first = Jordi | contribution = Family Rynchopidae (Skimmers) | title = [[Handbook of the Birds of the World]]. Volume 3, Hoatzin to Auks | year = 1996 | pages = 668–675 | place = Barcelona | publisher = Lynx Edicions | isbn = 84-87334-20-2 }}</ref>

Surface feeders that swim often have unique bills as well, adapted for their specific prey. [[Prion (bird)|Prions]] have special bills with filters called [[lamella (zoology)|lamellae]] to filter out [[plankton]] from mouthfuls of water,<ref name="Brooke">Brooke, M. (2004). ''Albatrosses and Petrels Across the World''. Oxford University Press, Oxford, UK {{ISBN|0-19-850125-0}}</ref> and many albatrosses and petrels have hooked bills to snatch fast-moving prey. On the other hand, most gulls are versatile and opportunistic feeders who will eat a wide variety of prey, both at sea and on land.<ref name="Davenport">{{cite book |last1=Davenport|first1=John|last2=D. Black|first2=Kenn|last3=Burnell|first3=Gavin|last4=Cross|first4=Tom|last5=Culloty|first5=Sarah|last6=Ekaratne|first6=Suki|last7=Furness|first7=Bob|last8=Mulcahy |first8=Maire|last9=Thetmeyer|first9=Helmut|date=2009|title=Aquaculture: The Ecological Issues|publisher=John Wiley & Sons|page=68|isbn=978-1444311259|url=https://books.google.com/books?id=304yeBTnjpYC&pg=PA68}}</ref>

==== Pursuit diving ====
[[File:African Penguin Skeleton.jpg|thumb|An [[African penguin]] skeleton, showing the sternal keel that makes the species a strong diver and swimmer]]
Pursuit diving exerts greater pressures (both evolutionary and physiological) on seabirds, but the reward is a greater area in which to feed than is available to surface feeders. Underwater [[Marine propulsion|propulsion]] is provided by wings (as used by penguins, auks, [[diving petrel]]s and some other species of petrel) or [[Bird feet and legs|feet]] (as used by cormorants, [[grebe]]s, [[loon]]s and several types of fish-eating [[duck]]s). Wing-propelled divers are generally faster than foot-propelled divers.<ref name="Burger" /> The use of wings or feet for diving has limited their utility in other situations: loons and grebes walk with extreme difficulty (if at all), penguins cannot fly, and auks have sacrificed flight efficiency in favour of diving. For example, the [[razorbill]] (an Atlantic auk) requires 64% more energy to fly than a petrel of equivalent size.<ref name="Auk">Gaston, Anthony J.; Jones, Ian L. (1998). ''The Auks'', Oxford University Press, Oxford, {{ISBN|0-19-854032-9}}</ref> Many [[shearwater]]s are intermediate between the two, having longer wings than typical wing-propelled divers but heavier wing loadings than the other surface-feeding [[procellariidae|procellariids]], leaving them capable of diving to considerable depths while still being efficient long-distance travellers. The [[short-tailed shearwater]] is the deepest diver of the shearwaters, having been recorded diving below {{convert|70|m|ft}}.<ref>{{cite journal|author1=Weimerskirch, H. |author2=Cherel, Y. |year=1998|title= Feeding ecology of short-tailed shearwaters: breeding in Tasmania and foraging in the Antarctic? |journal=Marine Ecology Progress Series |volume=167|pages= 261–274|doi=10.3354/meps167261|bibcode=1998MEPS..167..261W |doi-access=free }}</ref>

Some albatross species are also capable of limited diving, with [[light-mantled sooty albatross]]es holding the record at {{convert|12|m|ft|sigfig=1}}.<ref>{{cite journal|author1=Prince, P. A. |author2=Huin, N. |author3=Weimerskirch, H. |year=1994|title=Diving depths of albatrosses|journal=Antarctic Science |volume=6|issue=3|pages= 353–354|doi=10.1017/S0954102094000532|bibcode=1994AntSc...6..353P|s2cid=129728675 }}</ref> Of all the wing-propelled pursuit divers, the most efficient in the air are the albatrosses, and they are also the poorest divers. This is the dominant guild in polar and subpolar environments, but it is energetically inefficient in warmer waters. With their poor flying ability, many wing-propelled pursuit divers are more limited in their foraging range than other guilds.<ref name="Ulanski">{{cite book |last1=Ulanski|first1=Stan|date=2016|title=The California Current: A Pacific Ecosystem and Its Fliers, Divers, and Swimmers|publisher=UNC Press Books|page=99|isbn=978-0070294219|url=https://books.google.com/books?id=iWM3CwAAQBAJ&pg=PT99}}</ref>

==== Plunge diving ====
[[Gannet]]s, [[booby|boobies]], [[tropicbird]]s, some terns, and [[brown pelican]]s all engage in plunge diving, taking fast-moving prey by diving into the water from flight. Plunge diving allows birds to use the energy from the momentum of the dive to combat natural buoyancy (caused by air trapped in plumage),<ref>{{cite journal|author1=Ropert-Coudert, Y. |author2=Grémillet, D. |author3=Ryan, P. |author4=Kato, A. |author5=Naito, Y. |author6=Le Maho, Y. |year=2004|title= Between air and water: the plunge dive of the Cape Gannet ''Morus capensis''|journal=Ibis |volume=146 |issue=2 |pages= 281–290|doi=10.1111/j.1474-919x.2003.00250.x}}</ref> and thus uses less energy than the dedicated pursuit divers, allowing them to utilise more widely distributed food resources, for example, in impoverished [[tropics|tropical]] seas. In general, this is the most specialised method of hunting employed by seabirds; other non-specialists (such as gulls and skuas) may employ it but do so with less skill and from lower heights. In brown pelicans, the skills of plunge diving take several years to fully develop—once mature, they can dive from {{convert|20|m|ft|abbr=on}} above the water's surface, shifting the body before impact to avoid injury.<ref name ="elliot">{{ cite book | last=Elliot | first=A. | year=1992 | chapter=Family Pelecanidae (Pelicans) | editor1-last=del Hoyo | editor1-first=J. | editor2-last=Elliott | editor2-first=A. | editor3-last=Sargatal | editor3-first=J. | title=Handbook of the Birds of the World | volume=1: Ostrich to Ducks | place=Barcelona, Spain | publisher=Lynx Edicions | isbn=84-87334-10-5 | pages=290–311 | chapter-url=https://archive.org/details/handbookofbirdso0001unse/page/290/mode/1up | chapter-url-access=registration }}</ref>

It may be that plunge divers are restricted in their hunting grounds to clear waters that afford a view of their prey from the air.<ref>Ainley, D. G. (1977) "Feeding methods in seabirds: a comparison of polar and tropical nesting communities in the eastern Pacific Ocean". In: Llano, G. A. (Ed.). ''Adaptations within Antarctic ecosystems''. Smithsonian Inst. Washington D.C., pp. 669–685</ref> While they are the dominant [[Guild (ecology)|guild]] in the tropics, the link between plunge diving and [[water clarity]] is inconclusive.<ref>{{cite journal|author1=Haney, J. C.  |author2=Stone, A. E.  |name-list-style=amp |year=1988|title=Seabird foraging tactics and water clarity: Are plunge divers really in the clear?|journal=Marine Ecology Progress Series |volume=49|pages= 1–9|doi=10.3354/meps049001|bibcode=1988MEPS...49....1H  |doi-access=free}}</ref> Some plunge divers (as well as some surface feeders) are dependent on [[dolphin]]s and [[tuna]] to push shoaling fish up towards the surface.<ref name="AU">{{cite journal|author1=Au, D. W. K.  |author2=Pitman, R. L.  |name-list-style=amp |year=1986|title= Seabird interactions with Dolphins and Tuna in the Eastern Tropical Pacific|journal=Condor|volume=88|pages= 304–317|url=http://sora.unm.edu/sites/default/files/journals/condor/v088n03/p0304-p0317.pdf|doi=10.2307/1368877|issue=3|jstor=1368877 }}</ref>

==== Kleptoparasitism, scavenging and predation ====
This catch-all category refers to other seabird strategies that involve the next [[trophic level]] up. [[Kleptoparasitism|Kleptoparasites]] are seabirds that make a part of their living stealing food of other seabirds. Most famously, [[frigatebird]]s and [[skua]]s engage in this behaviour, although gulls, terns and other species will steal food opportunistically.<ref>{{cite journal|author1=Schnell, G. |author2=Woods, B. |author3=Ploger B. |year=1983|title=Brown Pelican foraging success and kleptoparasitism by Laughing Gulls|journal=Auk |volume=100|issue=3 |pages=636–644|doi=10.1093/auk/100.3.636 }}</ref> The [[nocturnal animal|nocturnal]] nesting behaviour of some seabirds has been interpreted as arising due to pressure from this aerial piracy.<ref>Gaston, A. J.; Dechesne, S. B. C. (1996). Rhinoceros Auklet (''Cerorhinca monocerata''). In ''The Birds of North America, No. 212'' (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, PA, and The American Ornithologists' Union, Washington, D.C.</ref> Kleptoparasitism is not thought to play a significant part of the diet of any species, and is instead a supplement to food obtained by hunting.<ref name="Burger" /> A study of [[great frigatebird]]s stealing from [[masked booby|masked boobies]] estimated that the frigatebirds could at most obtain 40% of the food they needed, and on average obtained only 5%.<ref>{{cite journal|author1=Vickery, J.  |author2=Brooke, M.  |year=1994|title=The kleptoparasitic interactions between Great Frigatebirds and Masked Boobies on Henderson Island, South Pacific |journal=Condor |volume=96|pages=331–340|doi=10.2307/1369318|issue=2|jstor=1369318 |s2cid=8846837 }}</ref> Many species of gull will feed on seabird and sea mammal [[carrion]] when the opportunity arises, as will [[giant petrel]]s. Some species of albatross also engage in scavenging: an analysis of regurgitated [[squid]] beaks has shown that many of the squid eaten are too large to have been caught alive, and include mid-water species likely to be beyond the reach of albatrosses.<ref>{{cite journal|author1=Croxall, J. P.  |author2=Prince, P. A.  |name-list-style=amp |year=1994|title=Dead or alive, night or day: how do albatrosses catch squid?|journal=Antarctic Science |volume=6|pages= 155–162|doi=10.1017/S0954102094000246|issue=2|bibcode=1994AntSc...6..155C|s2cid=86598155 }}</ref> Some species will also feed on other seabirds; for example, gulls, skuas and pelicans will often take eggs, chicks and even small adult seabirds from nesting colonies, while the giant petrels can kill prey up to the size of small penguins and seal pups.<ref>{{cite journal|last1=Punta |first1=G. |last2=Herrera |first2=G. |year=1995|title=Predation by Southern Giant Petrels ''Macronectes giganteus'' on adult Imperial Cormorants ''Phalacrocorax atriceps''|journal=Marine Ornithology |volume=23|pages= 166–167 |url=http://www.marineornithology.org/PDF/23_2/23_2_9.pdf}}</ref>

=== Life history ===
Seabirds' life histories are dramatically different from those of land birds. In general, they are [[K-selected]], live much longer (anywhere between twenty and sixty years), delay breeding for longer (for up to ten years), and invest more effort into fewer young.<ref name="Burger" /><ref>{{cite journal|author=Robertson, 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|pages= 269–276|doi=10.1071/MU9930269|issue=4|bibcode=1993EmuAO..93..269R }}</ref> Most species will only have one [[clutch (eggs)|clutch]] a year, unless they lose the first (with a few exceptions, like the [[Cassin's auklet]]),<ref>Manuwal, D. A. and Thoresen, A. C. (1993). Cassin's Auklet (''Ptychoramphus aleuticus''). In The Birds of North America, No. 50 (A. Poole and F. Gill, eds.). Philadelphia: The Academy of Natural Sciences; Washington, D.C.: The American Ornithologists' Union</ref> and many species (like the [[Procellariiformes|tubenoses]] and [[sulidae|sulids]]) will only lay one egg a year.<ref name="Brooke" />
[[File:Morus bassanus billing.jpg|thumb|[[Northern gannet]] pair "billing" during courtship; like all seabirds except the phalaropes they maintain a pair bond throughout the breeding season.]]
Care of young is protracted, extending for as long as six months, among the longest for birds. For example, once [[common guillemot]] chicks [[fledge]], they remain with the male parent for several months at sea.<ref name="Auk" /> The frigatebirds have the longest period of parental care of any bird except a few raptors and the [[southern ground hornbill]],<ref>See Skutch; Alexander Frank (author) and Gardner, Dana (illustrator) ''Helpers at birds' nests : a worldwide survey of cooperative breeding and related behavior''; pp. 69–71. Published 1987 by University of Iowa Press. {{ISBN|0-87745-150-8}}</ref> with each chick fledging after four to six months and continued assistance after that for up to fourteen months.<ref>Metz, V. G. and Schreiber, E. A. (2002) "Great Frigatebird (''Fregata minor'')" In ''The Birds of North America, No 681'', (Poole, A. and Gill, F., eds) The Birds of North America Inc.: Philadelphia</ref> Due to the extended period of care, breeding occurs every two years rather than annually for some species. This life-history strategy has probably evolved both in response to the challenges of living at sea (collecting widely scattered prey items), the frequency of breeding failures due to unfavourable marine conditions, and the relative lack of predation compared to that of land-living birds.<ref name="Burger" />

Because of the greater investment in raising the young and because foraging for food may occur far from the nest site, in all seabird species except the phalaropes, both parents participate in caring for the young, and pairs are typically at least seasonally [[Monogamy in animals|monogamous]]. Many species, such as gulls, auks and penguins, retain the same mate for several seasons, and many [[petrel]] species mate for life.<ref name="Brooke" /> Albatrosses and [[procellariid]]s, which mate for life, take many years to form a pair bond before they breed, and the albatrosses have an elaborate breeding dance that is part of pair-bond formation.<ref>{{cite journal|author1=Pickering, S. P. C.  |author2=Berrow, S. D. |name-list-style=amp |year=2001|title=Courtship behaviour of the Wandering Albatross ''Diomedea exulans'' at Bird Island, South Georgia|journal=Marine Ornithology |volume=29|pages= 29–37 |url=http://www.marineornithology.org/PDF/29_1/29_1_6.pdf}}</ref>

=== Breeding and colonies ===
{{See also|Bird colony|Seabird breeding behavior}}

[[File:Murre colony.jpg|thumb|right|[[Common murre|Common murres]] breed on densely packed colonies on offshore rocks, islands and cliffs.]]
Ninety-five percent of seabirds are colonial,<ref name="Burger" /> and seabird colonies are among the largest bird colonies in the world, providing one of Earth's great wildlife spectacles. Colonies of over a million birds have been recorded, both in the tropics (such as [[Kiritimati]] in the [[Pacific Ocean|Pacific]]) and in the polar latitudes (as in [[Antarctica]]). Seabird colonies occur exclusively for the purpose of breeding; non-breeding birds will only collect together outside the breeding season in areas where prey species are densely aggregated.<ref>{{Citation |last1=Kharitonov |first1=Sergei P. |title=Colony Formation in Seabirds |date=1988 |work=Current Ornithology |pages=223–272 |editor-last=Johnston |editor-first=Richard F. |url=https://doi.org/10.1007/978-1-4615-6787-5_5 |access-date=2024-04-19 |place=Boston, MA |publisher=Springer US |language=en |doi=10.1007/978-1-4615-6787-5_5 |isbn=978-1-4615-6787-5 |last2=Siegel-Causey |first2=Douglas|url-access=subscription }}</ref>

Seabird colonies are highly variable. Individual nesting sites can be widely spaced, as in an albatross colony, or densely packed as with a [[murre]] colony. In most seabird colonies, several different species will nest on the same colony, often exhibiting some [[Niche differentiation|niche separation]]. Seabirds can nest in trees (if any are available), on the ground (with or without [[bird nest|nests]]), on cliffs, in [[burrow]]s under the ground and in rocky crevices. Competition can be strong both within species and between species, with aggressive species such as [[sooty tern]]s pushing less dominant species out of the most desirable nesting spaces.<ref>Schreiber, E. A., Feare, C. J., Harrington, B. A., Murray, B. G., Jr., Robertson, W. B., Jr., Robertson, M. J. and Woolfenden, G. E. (2002). Sooty Tern (''Sterna fuscata''). In ''The Birds of North America'', No. '''665''' (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA</ref> The tropical [[Bonin petrel]] nests during the winter to avoid competition with the more aggressive [[wedge-tailed shearwater]]. When the seasons overlap, the wedge-tailed shearwaters will kill young Bonin petrels in order to use their burrows.<ref>Seto, N. W. H. and O'Daniel, D. (1999) Bonin Petrel (''Pterodroma hypoleuca''). In ''The Birds of North America, No. 385'' (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA</ref>

Many seabirds show remarkable site [[fidelity]], returning to the same burrow, nest or site for many years, and they will defend that site from rivals with great vigour.<ref name="Burger" /> This increases breeding success, provides a place for returning mates to reunite, and reduces the costs of prospecting for a new site.<ref>{{cite journal|author1=Bried, J. L. |author2=Pontier, D. |author3=Jouventin, P. |year=2003|title=Mate fidelity in monogamous birds: a re-examination of the Procellariiformes|journal=Animal Behaviour |volume=65|pages= 235–246|doi=10.1006/anbe.2002.2045|s2cid=53169037 }}</ref> Young adults breeding for the first time usually return to their natal colony, and often nest close to where they hatched. This tendency, known as [[philopatry]], is so strong that a study of [[Laysan albatross]]es found that the average distance between hatching site and the site where a bird established its own territory was {{convert|22|m|ft}};<ref>{{cite journal|author=Fisher, H. I. |year=1976|title=Some dynamics of a breeding colony of Laysan Albatrosses|url=http://sora.unm.edu/node/129258|jstor=4160718|journal=Wilson Bulletin |volume=88|issue=1|pages= 121–142}}</ref> another study, this time on [[Cory's shearwater]]s nesting near [[Corsica]], found that of nine out of 61 male chicks that returned to breed at their natal colony bred in the burrow they were raised in, and two actually bred with their own mother.<ref>{{cite journal|author1=Rabouam, C. |author2=Thibault, J.-C. |author3=Bretagnole, V. |year=1998|title=Natal Philopatry and close inbreeding in Cory's shearwater (''Calonectris diomedea'')|journal=Auk |volume=115 |issue=2 |pages= 483–486 |url=http://sora.unm.edu/sites/default/files/journals/auk/v115n02/p0483-p0486.pdf|doi=10.2307/4089209|jstor=4089209 }}</ref>

Colonies are usually situated on islands, cliffs or headlands, which land mammals have difficulty accessing.<ref name ="Moors">Moors, P. J.; Atkinson, I. A. E. (1984). ''Predation on seabirds by introduced animals, and factors affecting its severity''. In ''Status and Conservation of the World's Seabirds''. Cambridge: ICBP. {{ISBN|0-946888-03-5}}</ref> This is thought to provide protection to seabirds, which are often very clumsy on land. Coloniality often arises in types of birds that do not defend feeding territories (such as [[Swift (bird)|swift]]s, which have a very variable prey source); this may be a reason why it arises more frequently in seabirds.<ref name="Burger" /> There are other possible advantages: colonies may act as information centres, where seabirds returning to the sea to forage can find out where prey is by studying returning individuals of the same species. There are disadvantages to colonial life, particularly the spread of disease. Colonies also attract the attention of [[predation|predators]], principally other birds, and many species attend their colonies nocturnally to avoid predation.<ref>{{cite journal|author1=Keitt, B. S. |author2=Tershy, B. R. |author3=Croll, D. A. |year=2004|title=Nocturnal behavior reduces predation pressure on Black-vented Shearwaters ''Puffinus opisthomelas''|journal=Marine Ornithology |volume=32|issue=3 |pages= 173–178|url=http://www.marineornithology.org/PDF/32_2/32_2_173-178.pdf}}</ref> Birds from different colonies often forage in different areas to avoid competition.<ref>{{Cite journal|last1=Bolton|first1=Mark|last2=Conolly|first2=Georgia|last3=Carroll|first3=Matthew|last4=Wakefield|first4=Ewan D.|last5=Caldow|first5=Richard|date=2019|title=A review of the occurrence of inter-colony segregation of seabird foraging areas and the implications for marine environmental impact assessment|journal=Ibis|language=en|volume=161|issue=2|pages=241–259|doi=10.1111/ibi.12677|issn=1474-919X|doi-access=free}}</ref>

=== Migration ===
{{Multiple image
| total_width       = 360
| image1            = PelicanosFlock.jpg
| alt1              = 
| caption1          = [[Pelicans|Pelican]] flock flying over [[Havana]] Bay area. These birds come to [[Cuba]] every year from North America in the northern hemisphere winter season.
| image2            = Smallarctern.jpg
| alt2              = 
| caption2          = [[Arctic tern]]s breed in the arctic and subarctic and winter in Antarctica.
}}
Like many birds, seabirds often [[bird migration|migrate]] after the [[breeding season]]. Of these, the trip taken by the [[Arctic tern]] is the farthest of any bird, crossing the [[equator]] in order to spend the Austral summer in Antarctica. Other species also undertake trans-equatorial trips, both from the north to the south, and from south to north. The population of [[elegant tern]]s, which nest off [[Baja California]], splits after the breeding season with some birds travelling north to the [[Central Coast of California]] and some travelling as far south as Peru and Chile to feed in the [[Humboldt Current]].<ref>Burness, G. P., Lefevre, K. and Collins, C. T. (1999). Elegant Tern (''Sterna elegans''). In ''The Birds of North America'', No. '''404''' (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA</ref> The [[sooty shearwater]] undertakes an annual migration cycle that rivals that of the Arctic tern; birds that nest in New Zealand and Chile and spend the northern summer feeding in the North Pacific off Japan, Alaska and California, an annual round trip of {{convert|40000|smi|km|order=flip}}.<ref>{{cite journal|author1=Shaffer, S. A. |author2=Tremblay, Y. |author3=Weimerskirch, H. |author4=Scott, D. |author5=Thompson, D. R. |author6=Sagar, P. M. |author7=Moller, H. |author8=Taylor, G. A. |author9=Foley, D. G. |author10=Block, B. A. |author11=Costa, 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 |volume=103 |issue=34 |pages= 12799–12802|doi=10.1073/pnas.0603715103|pmid=16908846|pmc=1568927|bibcode=2006PNAS..10312799S |doi-access=free }}</ref>

Other species also migrate shorter distances away from the breeding sites, their distribution at sea determined by the availability of food. If oceanic conditions are unsuitable, seabirds will emigrate to more productive areas, sometimes permanently if the bird is young.<ref>{{cite journal|author1=Oro, D. |author2=Cam, E. |author3=Pradel, R. |author4=Martinetz-Abrain, A. |year=2004|title=Influence of food availability on demography and local population dynamics in a long-lived seabird|journal=[[Proceedings of the Royal Society B]] |volume=271|pages= 387–396|doi=10.1098/rspb.2003.2609|issue=1537 |pmid=15101698 |pmc=1691609}}</ref> After fledging, juvenile birds often disperse further than adults, and to different areas, so are commonly sighted far from a species' normal range. Some species, such as the auks, do not have a concerted migration effort, but drift southwards as the winter approaches.<ref name="Auk" /> Other species, such as some of the storm petrels, diving petrels and cormorants, never disperse at all, staying near their breeding colonies year round.<ref>{{Citation |last1=Winkler |first1=David W. |title=Northern Storm-Petrels (Hydrobatidae) |date=2020-03-04 |url=https://birdsoftheworld.org/bow/species/hydrob1/1.0/introduction |work=Birds of the World |editor-last=Billerman |editor-first=Shawn M. |publisher=Cornell Lab of Ornithology |language=en |doi=10.2173/bow.hydrob1.01 |access-date=2022-04-23 |last2=Billerman |first2=Shawn M. |last3=Lovette |first3=Irby J. |s2cid=216364538 |editor2-last=Keeney |editor2-first=Brooke K. |editor3-last=Rodewald |editor3-first=Paul G. |editor4-last=Schulenberg |editor4-first=Thomas S.|url-access=subscription }}</ref><ref>{{Cite journal |last1=Carboneras |first1=Carles |last2=Jutglar |first2=Francesc |last3=Kirwan |first3=Guy M. |date=2020 |title=Common Diving-Petrel (Pelecanoides urinatrix), version 1.0 |url=https://birdsoftheworld.org/bow/species/codpet1/cur/introduction |journal=Birds of the World |language=en |doi=10.2173/bow.codpet1.01|s2cid=226017737 |url-access=subscription }}</ref><ref>{{Citation |last1=Orta |first1=Jaume |title=Little Black Cormorant (Phalacrocorax sulcirostris) |date=2020-03-04 |url=https://birdsoftheworld.org/bow/species/libcor1/1.0/introduction |work=Birds of the World |editor-last=Billerman |editor-first=Shawn M. |publisher=Cornell Lab of Ornithology |language=en |doi=10.2173/bow.libcor1.01 |access-date=2022-04-22 |last2=Christie |first2=David |last3=Jutglar |first3=Francesc |last4=Kirwan |first4=Guy M. |s2cid=226397614 |editor2-last=Keeney |editor2-first=Brooke K. |editor3-last=Rodewald |editor3-first=Paul G. |editor4-last=Schulenberg |editor4-first=Thomas S.|url-access=subscription }}</ref>

=== Away from the sea ===
While the definition of seabirds suggests that the birds in question spend their lives on the ocean, many seabird families have many species that spend some or even most of their lives inland away from the sea. Most strikingly, many species breed tens, hundreds or even thousands of miles inland. Some of these species still return to the ocean to feed; for example, the [[snow petrel]], the nests of which have been found {{convert|480|km|mi}} inland on the Antarctic mainland, are unlikely to find anything to eat around their breeding sites.<ref>{{cite journal|author1=Croxall, J |author2=Steele, W. |author3=McInnes, S. |author4=Prince, P. |year=1995|title= Breeding Distribution of Snow Petrel ''Pagodroma nivea''|journal=Marine Ornithology |volume=23|pages= 69–99|url=http://www.marineornithology.org/PDF/23_2/23_2_1.pdf}}</ref> The [[marbled murrelet]] nests inland in [[old growth forest]], seeking huge [[conifer]]s with large branches to nest on.<ref>Nelson, S. K. (1997). Marbled Murrelet (''Brachyramphus marmoratus''). In ''The Birds of North America'', No. 276 (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, PA, and The American Ornithologists' Union, Washington, D.C</ref> Other species, such as the [[California gull]], nest and feed inland on lakes, and then move to the coasts in the winter.<ref>Winkler, D. W. (1996). California Gull (''Larus californicus''). In ''The Birds of North America'', No. 259 (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, PA, and The American Ornithologists' Union, Washington, D.C.</ref> Some cormorant, [[pelican]], gull and tern species have individuals that never visit the sea at all, spending their lives on lakes, rivers, [[swamp]]s and, in the case of some of the gulls, cities and [[agriculture|agricultural]] land. In these cases, it is thought that these terrestrial or freshwater birds evolved from marine ancestors.<ref name="Gaston" /> Some seabirds, principally those that nest in [[tundra]], as skuas and phalaropes do, will migrate over land as well.<ref name="Rubega"/><ref name="Wiley">{{cite journal |url= https://birdsoftheworld.org/bow/species/parjae/cur/movement |title= Parasitic Jaeger (''Stercorarius parasiticus'' |series=Version 1.0 |url-access=subscription |last1=Wiley|first1= R. Haven|last2= Lee| first2= David S. |editor-first1= Shawn M. |editor-last1= Billerman |date=March 4, 2020 |journal=Birds of the World |publisher=Cornell Lab of Ornithology |doi= 10.2173/bow.parjae.01|s2cid= 216364499|access-date=March 26, 2021}}</ref>

The more marine species, such as petrels, auks and [[gannet]]s, are more restricted in their habits, but are occasionally seen inland as vagrants. This most commonly happens to young inexperienced birds, but can happen in great numbers to exhausted adults after large [[storm]]s, an event known as a ''wreck''.<ref>{{cite journal|author1=Harris, M.  |author2=Wanless, S.  |name-list-style=amp |year=1996|title=Differential responses of Guillemot ''Uria aalge'' and Shag ''Phalacrocorax aristotelis'' to a late winter wreck|journal=Bird Study |volume=43 |issue=2 |pages= 220–230|doi=10.1080/00063659609461014|bibcode=1996BirdS..43..220H |bibcode-access=free |doi-access=free}}</ref>