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[[Berkas:Sterna fuscata flight.JPG|thumbjmpl|alt = Burung laut terbang di langit yang biru|rightka|[[Dara-laut Jelaga]] dapat menghabiskan waktu berbulan bulan terbang di atas laut dan hanya kembali ke daratan untuk berkembang biak.<ref>{{IUCN2008|assessors=BirdLife International (BLI)|year=2008|id=144265|title=Sterna fuscata|downloaded=7 August 2009}}</ref>]]
'''Burung laut''' adalah [[burung]] yang telah ber[[adaptasi]] dengan kehidupan lingkungan laut. Meskipun burung laut sangat beragam dalam gaya hidup, perilaku dan fisiologi, mereka sering memperlihatkan evolusi konvergen yang mencolok, karena permasalahan lingkungan dan ladang makanan yang sama telah mengakibatkan adaptasi yang sama. Para burung laut pertama kali berevolusi pada periode [[Cretaceous]], dan keluarga burung laut modern muncul pada masa [[Paleogen]].
 
Baris 11:
[[Loon]] dan [[Titihan]], yang bersarang di [[danau]] namun melewatkan musim dingin di laut, biasanya dikelompokkan dalam burung air tawar, bukan burung laut. Begitu pula suku [[Anatidae]] (bebek-bebekan), yang meskipun beberapa anggotanya hidup di [[laut]] semasa [[musim dingin]], berdasarkan kesepakatan dianggap bukan burung laut. Banyak jenis burung perancah dan bangau yang hidup di pesisir [[pantai]], namun tidak pula dikategorikan sebagai burung laut.
 
== Evolusi dan catatan fosil ==
<!--Seabirds, by virtue of living in a [[geology|geologically]] depositional environment (that is, in the sea where [[sediment]]s are readily laid down), are well represented in the [[fossil]] record.<ref name = "Burger"/> They are first known to occur in the [[Cretaceous]] Period, the earliest being the [[Hesperornithiformes]], like ''Hesperornis regalis'', a flightless loon-like seabird that dove in a fashion similar to grebes and loons (using its feet to move underwater)<ref>Johansson LC, Lindhe Norberg UM. (2001) "Lift-based paddling in diving grebe." ''J Exp Biol.'' '''204'''(10) :1687–96.[http://jeb.biologists.org/cgi/reprint/204/10/1687]</ref> but had a beak filled with sharp teeth.<ref>Gregory, J. (1952) "The Jaws of the Cretaceous Toothed Birds, Ichthyornis and Hesperornis" ''Condor'' '''54'''(2): 73–88 [http://elibrary.unm.edu/sora/Condor/files/issues/v054n02/p0073-p0088.pdf#search=%22The%20Jaws%20of%20the%20Cretaceous%20Toothed%20Birds%2C%20Ichthyornis%20and%20Hesperornis%20%22]</ref>
[[Berkas:Hesperornis.jpeg|thumb|350px|right|alt = skull of ancient seabird with teeth set into bill|The Cretaceous seabird ''Hesperornis'']]
 
While ''Hesperornis'' is not thought to have left descendants, the earliest [[Neornithes|modern]] seabirds also occurred in the Cretaceous, with a species called ''[[Tytthostonyx glauconiticus]]'', which seems allied to the [[Procellariiformes]] and/or [[Pelecaniformes]]. In the [[Paleogene]] the seas were dominated by early [[Procellariidae]], giant [[penguin]]s and two [[extinct]] [[family (biology)|families]], the [[Pelagornithidae]] and the [[Plotopteridae]] (a group of large seabirds that looked like the penguins).<ref>Goedert, J. (1989) "Giant Late Eocene Marine Birds (Pelecaniformes: Pelagornithidae) from Northwestern Oregon" ''Journal of Paleontology'', '''63'''(6) 939–944</ref> Modern genera began their wide radiation in the [[Miocene]], although the [[genus]] ''[[Puffinus]]'' (which includes today's [[Manx Shearwater]] and [[Sooty Shearwater]]) might date back to the [[Oligocene]].<ref name="Burger"/> The highest diversity of seabirds apparently existed during the Late Miocene and the [[Pliocene]]. At the end of the latter, the oceanic [[food web]] had undergone a period of upheaval due to extinction of considerable numbers of marine species;<ref>Possibly due to comparatively close (in astronomical terms – c. 150 [[light-year]]s) [[supernova]] activity</ref> subsequently, the spread of marine mammals seems to have prevented seabirds from reaching their erstwhile diversity.<ref>Olson, S. & Hasegawa, Y. (1979)"Fossil Counterparts of Giant Penguins from the North Pacific" ''[[Science (journal)|Science]]'' '''206'''(4419): 688–689.</ref>
 
==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, whilst 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]] called [[dynamic soaring]] (where the wind deflected by waves provides lift) as well as slope soaring.<ref>Pennycuick, C. J. (1982). "The flight of petrels and albatrosses (Procellariiformes), observed in South Georgia and its vicinity". ''Philosophical Transactions of the Royal Society of London B'' '''300''': 75–106.</ref> Seabirds also almost always have webbed feet, to aid movement on the surface as well as assisting diving in some species. The [[Procellariiformes]] are unusual amongst birds in having a strong [[olfaction|sense of smell]], which is used to find widely distributed food in a vast ocean,<ref>Lequette, B., Verheyden, C., Jowentin, P. (1989) "Olfaction in Subantarctic seabirds: Its phylogenetic and ecological significance" ''The Condor'' '''91''': 732-135. [http://elibrary.unm.edu/sora/Condor/files/issues/v091n03/p0732-p0735.pdf]</ref> and possibly to locate their colonies.
 
[[Supraorbital gland|Salt gland]]s 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'' Ithica: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]].
[[Berkas:Phalacrocorax-auritus-007.jpg|thumb|left|Cormorants, like this [[Double-crested Cormorant|Double-Crested Cormorant]], have plumage that is partly wettable, allowing them to dive without fighting buoyancy.]]
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 feathers]]. 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>Grémillet, D, Chauvin, C, Wilson, R.P., Le Maho, Y. & Wanless, S. (2005) Unusual feather structure allows partial plumage wettability in diving great cormorants ''Phalacrocorax carbo''." ''Journal of Avian Biology'' '''36'''(1): 57–63.</ref> 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.
 
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 or 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).
 
===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 [[auk]]s and [[penguin]]s. 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.
 
====Surface feeding====
Many seabirds feed on the ocean's surface, as the action of marine [[ocean current|current]]s often concentrates food such as [[krill]], [[forage fish]], [[squid]] or other prey items within reach of a dipped head.
[[Berkas:Wilson's storm petrel.jpg|thumb|300px|[[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 whilst swimming (examples of which are practiced by [[fulmar]]s, [[gull]]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 frigate-birds and some terns), or "walk", pattering and hovering on the water's surface, as some of the storm-petrels do.<ref>Withers, P.C (1979) "Aerodynamics and Hydrodynamics of the ‘Hovering’ Flight of Wilson'S Storm Petrel" ''Journal of Experimental Biology'' '''80''': 83–91 [http://jeb.biologists.org/cgi/reprint/80/1/83]</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 E. A. Schreiber. 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]], 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.
 
Surface feeders that swim often have unique bills as well, adapted for their specific prey. [[Prion (bird)|Prion]]s have special bills with filters called [[lamella (zoology)|lamella]]e 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. Gulls have more generalised bills that reflect their more opportunistic lifestyle.
 
====Pursuit diving====
[[Berkas:Penguinu.jpg|thumb|alt = penguin leaping out of water|left|The [[Chinstrap Penguin]] is a highly streamlined pursuit diver.]]
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. [[Marine propulsion|Propulsion]] underwater can be provided by wings (as used by penguins, auks, [[diving petrel]]s, and some other species of petrel) or feet (as used by [[cormorant]]s, [[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"/> In both cases, 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), [[penguin]]s cannot fly, and auks have sacrificed flight efficiency in favour of underwater 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:Oxford University Press, 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|procellariid]]s, leaving them capable of diving to considerable depths while still being efficient long-distance travellers. The most impressive diving exhibited by shearwaters is found in the [[Short-tailed Shearwater]], which has been recorded diving below 70&nbsp;m.<ref>Weimerskirch, H., Cherel, Y., (1998) Feeding ecology of short-tailed shearwaters: breeding in Tasmania and foraging in the Antarctic? ''Marine Ecology Progress Series'' '''167''': 261–274</ref> Some albatross species are also capable of some limited diving, with [[Light-mantled Sooty Albatross]]es holding the record at 12&nbsp;m.<ref>Prince, P.A., Huin, N., Weimerskirch, H., (1994) "Diving depths of albatrosses" ''Antarctic Science'' '''6''': (''3'') 353–354.</ref> Of all the wing-propelled pursuit divers, the most efficient in the air are the [[albatross]]es, and it is no coincidence that they are the poorest divers. This is the dominant guild in polar and subpolar environments, as 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, especially during the breeding season when hungry chicks need regular feeding.
 
====Plunge diving====
[[Gannet]]s, [[booby|boobies]], [[tropicbird]]s, some [[tern]]s 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>Ropert-Coudert Y., Grémillet D., Ryan P., Kato A., Naito Y. & Le Maho Y. (2004) " Between air and water: the plunge dive of the Cape Gannet ''Morus capensis''" ''Ibis'' '''146'''(2): 281–290</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 20&nbsp;m (70&nbsp;ft) above the water's surface, shifting the body before impact to avoid injury.<ref name="elliot">Elliot, A. (1992) "Family Pelecanidae (Pelicans)" in ''Handbook of Birds of the World'' Vol 1. Barcelona:Lynx Editions, ISBN 84-87334-10-5</ref> It has been suggested 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. P 669–685.</ref> and while they are the dominant guild in the tropics, the link between plunge diving and water clarity is inconclusive.<ref>Haney, J.C. & Stone, A.E. (1988) "Seabird foraging tactics and water clarity: Are plunge divers really in the clear?" ''Marine Ecology Progress Series'' '''49''' 1–9</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">Au, D.W.K. & Pitman, R.L. (1986) Seabird interactions with Dolphins and Tuna in the Eastern Tropical Pacific. ''Condor'', '''88''': 304–317. [http://elibrary.unm.edu/sora/Condor/files/issues/v088n03/p0304-p0317.pdf]</ref>
 
====Kleptoparasitism, scavenging and predation====
[[Berkas:Skua and penguin.jpeg|thumb|left|alt = dark gull-like bird with raised wings facing off penguin on nest|Some seabirds, like this [[South Polar Skua]] (left), will take the eggs of other birds. This skua is attempting to push an [[Adelie Penguin]] (right) off its nest.]]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>Schnell, G., Woods, B & Ploger B (1983) "Brown Pelican foraging success and kleptoparasitism by Laughing Gulls" ''Auk'' '''100''':636–644</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., and S. B. C. Dechesne. (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>Vickery, J & Brooke, M. (1994) "The Kleptoparasitic Interactions between Great Frigatebirds and Masked Boobies on Henderson Island, South Pacific
" ''Condor'' '''96''': 331–340</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>Croxall, J.P. & Prince, P.A. (1994). "Dead or alive, night or day: how do albatrosses catch squid?" ''Antarctic Science'' '''6''': 155–162.</ref> Some species will also feed on other seabirds; for example, gulls, skuas and giant petrels will often take eggs, chicks and even small adult seabirds from nesting colonies.<ref>Punta, G, Herrera, G. (1995) "Predation by Southern Giant Petrels ''Macronectes giganteus'' on adult Imperial Cormorants ''Phalacrocorax atriceps''" ''Marine Ornithology'' '''23''' 166-167 [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>Robertson, C.J.R. (1993). "Survival and longevity of the Northern Royal Albatross ''Diomedea epomophora sanfordi'' at Taiaroa Head" 1937–93. ''Emu'' '''93''': 269–276.</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 A. C. Thoresen. 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|sulid]]s), only one egg a year.<ref name = "Brooke"/>
[[Berkas: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 [[frigatebird]]s have the longest period of parental care of any bird, with the chicks fledging after four to six months and with continued assistance after that for up to fourteen months.<ref>Metz, V.G. & Schreiber, E.A. (2002) "Great Frigatebird (''Fregata minor'')" In ''The Birds of North America, No 681'', (Poole, A. & 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 [[Animal sexuality#Monogamy|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"/> The albatrosses and [[procellariid]]s which mate for life can 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>Pickering, S.P.C., & Berrow, S.D., (2001) "Courtship behaviour of the Wandering Albatross ''Diomedea exulans'' at Bird Island, South Georgia" ''Marine Ornithology'' '''29''': 29–37 [http://www.marineornithology.org/PDF/29_1/29_1_6.pdf]</ref>
 
===Breeding and colonies===
:''See also [[Bird colony|Seabird colony]]
:''See also [[Unusual Seabird Breeding Behavior]]
 
[[Berkas:Murre colony.jpg.jpeg|thumb|right|[[Common Guillemot|Common Murre]]s breed on densely packed colonies on offshore rocks, islands and cliffs.]]
Ninety-five per cent of seabirds are colonial,<ref name = "Burger"/> and seabird colonies are amongst 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.
 
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 [[ecological niche|niche]] separation. Seabirds can nest in [[tree]]s (if any are available), on the ground (with or without [[bird nest|nest]]s), on [[cliff]]s, 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., C. J. Feare, B. A. Harrington, B. G. Murray, Jr., W. B. Robertson, Jr., M. J. Robertson, and G. E. Woolfenden. 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 D. O'Daniel. (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>Bried, J.L., Pontier, D., Jouventin, P., (2003) "Mate fidelity in monogamous birds: a re-examination of the Procellariiformes" ''Animal Behaviour'' '''65''': 235–246</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 22&nbsp;m;<ref>Fisher, H.I., (1976) "Some dynamics of a breeding colony of Laysan Albatrosses. ''Wilson Bulletin'' '''88''': 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>Rabouam, C., Thibault, J.-C., Bretagnole, V., (1998) "Natal Philopatry and Close Inbreeding in Cory's Shearwater (''Calonectris diomedea'')" ''Auk'' '''115'''(2): 483–486 [http://elibrary.unm.edu/sora/Auk/v115n02/p0483-p0486.pdf]</ref>
 
Colonies are usually situated on islands, cliffs or headlands which land [[mammal]]s 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 bird which do not defend feeding territories (such as [[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 [[nocturnal animal|nocturnally]] to avoid predation.<ref>Keitt, B.S., Tershy, B.R. & Croll, D.A (2004). "Nocturnal behavior reduces predation pressure on Black-vented Shearwaters ''Puffinus opisthomelas''" ''Marine Ornithology'' '''32''' (3): 173-178.[http://www.marineornithology.org/PDF/32_2/32_2_173-178.pdf]</ref>
 
===Migration===
[[Berkas:PelicanosFlock.jpg|thumb|left|[[Pelicans]] flock flying over [[Havana]] Bay area. These birds come to [[Cuba]] every year from [[North America]] in the north hemisphere winter season.]][[Berkas:Smallarctern.jpg|thumb|left|Arctic Terns 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., K. Lefevre, and C. T. Collins. 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}}.<ref>Shaffer S.A., Tremblay Y., Weimerskirch H., Scott D., Thompson D.R., Sagar P.M., Moller H., Taylor G.A., Foley D.G., Block B.A., Costa D.P. (2006) "Migratory shearwaters integrate oceanic resources across the Pacific Ocean in an endless summer." ''Proc Natl Acad Sci.'' '''103'''(34): 12799–12802</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>Oro, D., Cam, E., Pradel, R. & Martinetz-Abrain, A. (2004) "Influence of food availability on demography and local population dynamics in a long-lived seabird" ''Proc. R. Soc. London B.'' '''271''':387–396</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 petrel]]s, [[diving petrel]]s and [[cormorant]]s, never disperse at all, staying near their breeding colonies year round.
 
===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 many 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>Croxall, J, Steele, W., McInnes, S, Prince, P. (1995)"Breeding Distribution of Snow Petrel ''Pagodroma nivea''" ''Marine Ornithology'' '''23''' 69–99 [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 [[lake]]s, 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]]-like skuas and phalaropes, will migrate over land as well.
 
The more marine species, such as [[petrel]]s, [[auk]]s, 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>Harris, M. & Wanless, S., (1996) "Differential responses of Guillemot ''Uria aalge'' and Shag ''Phalacrocorax aristotelis'' to a late winter wreck" ''Bird Study'' '''43'''(2): 220–230</ref> where they provide prized sightings for [[birdwatching|birders]].
 
==Relationship with humans==
===Seabirds and fisheries===
Seabirds have had a long association with both [[fishery|fisheries]] and [[sailor]]s, and both have drawn benefits and disadvantages from the relationship.
 
Fishermen have traditionally used seabirds as indicators of both [[Shoaling and schooling|fish shoals]],<ref name="AU"/> underwater [[bank (topography)|banks]] that might indicate fish stocks, and of potential landfall. In fact, the known association of seabirds with land was instrumental in allowing the [[Polynesia]]ns to locate tiny landmasses in the Pacific.<ref name = "Burger"/> Seabirds have provided food for fishermen away from home, as well as bait. Famously, tethered [[cormorant]]s have been used to catch fish directly. Indirectly, fisheries have also benefited from [[guano]] from colonies of seabirds acting as [[fertilizer]] for the surrounding seas.
 
Negative effects on fisheries are mostly restricted to raiding by birds on [[aquaculture]],<ref>Collis, K., Adamany, S. – Columbia River Inter-Tribal Fish Commission, Roby, D.D., Craig, D.P., Lyons, D.E., – Oregon Cooperative Fish and Wildlife Research Unit, (2000), "Avian Predation on Juvenile Salmonids in the Lower Columbia River", ''1998 Annual Report to Bonneville Power Administration'', Portland, OR,[http://www.govdocs.aquake.org/cgi/reprint/2004/915/9150520.pdf]</ref> although [[long-line fishing|long-lining]] fisheries also have to deal with [[bait (luring substance)|bait]] stealing. There have been claims of prey depletion by seabirds of fishery stocks, and while there is some evidence of this, the effects of seabirds are considered smaller than that of [[marine mammal]]s and predatory fish (like [[tuna]]).<ref name = "Burger"/>
 
[[Berkas:Seabirds longlinersm.jpg.jpeg|thumb|300px|right|Seabirds (mostly Northern Fulmars) flocking at a long-lining vessel]]Some seabird species have benefited from fisheries, particularly from discarded fish and [[offal]]. These discards compose 30% of the food of seabirds in the [[North Sea]], for example, and compose up to 70% of the total food of some seabird populations.<ref>Oro, D., Ruiz, X., Pedrocchi, V. & Gonzalez-Solis, J. (1997) "Diet and adult time budgets of Audouin's Gull ''Larus audouinii'' in response to changes in commercial fisheries" ''Ibis'' '''139''': 631–637</ref> This can have other impacts; for example, the spread of the [[Northern Fulmar]] through the [[United Kingdom]] is attributed in part to the availability of discards.<ref>Thompson, P.M., (2004) "Identifying drivers of change; did fisheries play a role in the spread of North Atlantic fulmars?" in '' Management of marine ecosystems: monitoring change in upper trophic levels''. Cambridge: Cambridge University Press [http://www.abdn.ac.uk/lighthouse/documents/Thompson_fulmars.pdf]</ref> Discards generally benefit surface feeders, such as gannets and petrels, to the detriment of pursuit divers like penguins.
 
Fisheries also have negative effects on seabirds, and these effects, particularly on the long-lived and slow-breeding albatrosses, are a source of increasing concern to conservationists. The bycatch of seabirds entangled in nets or hooked on fishing lines has had a big impact on seabird numbers; for example, an estimated 100,000 albatrosses are hooked and drown each year on tuna lines set out by long-line fisheries.<ref>BirdLife International/RSPB (2005) [http://www.savethealbatross.net/the_problem.asp Save the Albatross: The Problem] Retrieved March 17, 2006</ref><ref>Brothers NP. 1991. "Albatross mortality and associated bait loss in the Japanese longline fishery in the southern ocean." ''Biological Conservation'' '''55''': 255–268.</ref> Overall, many hundreds of thousands of birds are trapped and killed each year, a source of concern for some of the rarest species (for example, only about 2,000 [[Short-tailed Albatross]]es are known to still exist). Seabirds are also thought to suffer when overfishing occurs.
 
===Exploitation===
The [[hunting]] of seabirds and the collecting of seabird [[egg (biology)|eggs]] have contributed to the declines of many species, and the [[extinct]]ion of several, including the [[Great Auk]] and the [[Spectacled Cormorant]]. Seabirds have been hunted for food by coastal peoples throughout history—one of the earliest instances known is in southern [[Chile]], where [[archeology|archaeological]] excavations in middens has shown hunting of albatrosses, cormorants and shearwaters from 5000 BP.<ref>Simeone, A. & Navarro, X. (2002) "Human exploitation of seabirds in coastal southern Chile during the mid-Holocene" ''Rev. chil. hist. nat'' '''75'''(2): 423–431 [http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-078X2002000200012&lng=es&nrm=iso&tlng=en]</ref> This pressure has led to some species becoming extinct in many places; in particular, at least 20 species of an original 29 no longer breed on [[Easter Island]]. In the 19th century, the hunting of seabirds for [[fat]] deposits and feathers for the [[Hat|millinery]] trade reached [[industry|industrial]] levels. [[Muttonbird]]ing (harvesting shearwater chicks) developed as important industries in both New Zealand and Tasmania, and the name of one species, the [[Providence Petrel]], is derived from its seemingly miraculous arrival on [[Norfolk Island]] where it provided a windfall for starving European settlers.<ref name = "Anderson">Anderson, A. (1996) "Origins of Procellariidae Hunting in the Southwest Pacific" ''International Journal of Osteoarcheology'' '''6''': 403–410</ref> In the [[Falkland Islands]], hundreds of thousands of penguins were harvested for their oil each year. Seabird eggs have also long been an important source of food for sailors undertaking long sea voyages, as well as being taken when settlements grow in areas near a colony. Eggers from [[San Francisco, California|San Francisco]] took almost half a million eggs a year from the [[Farallon Islands]] in the mid-19th century, a period in the islands' history from which the seabird species are still recovering.<ref>White, Peter; (1995), The Farallon Islands, ''Sentinels of the Golden Gate'', Scottwall Associates:San Francisco, ISBN 0-942087-10-0</ref>
 
Both hunting and egging continue today, although not at the levels that occurred in the past, and generally in a more controlled manner. For example, the [[Māori people|Māori]] of [[Stewart Island/Rakiura]] continue to harvest the chicks of the [[Sooty Shearwater]] as they have done for centuries, using traditional methods (called ''[[kaitiaki]]tanga'') to manage the harvest, but now work with the [[University of Otago]] in studying the populations. In [[Greenland]], however, uncontrolled hunting is pushing many species into steep decline.<ref>Burnham, W., Burnham, K.K., Cade, T.J., (2005) "Past and present assessments of bird life in Uummannaq District, West Greenland" ''Dansk Orn. Foren. Tidsskr.'' '''99''': 196–208 [http://www.birdlife.org/news/news/2006/01/birdlife_in_uummannaq.pdf]</ref>
 
===Other threats===
 
*''See Also:'' [[Introduced mammals on seabird breeding islands]]
 
Other human factors have led to declines and even extinctions in seabird populations, colonies and species. Of these, perhaps the most serious are [[introduced species]]. Seabirds, breeding predominantly on small isolated islands, have lost many predator defence behaviours.<ref name="Moors"/> [[Feral cat]]s are capable of taking seabirds as large as albatrosses, and many introduced rodents, such as the [[Polynesian Rat|Pacific Rat]], can take eggs hidden in burrows. Introduced [[goat]]s, [[cattle]], [[rabbit]]s and other [[herbivore]]s can lead to problems, particularly when species need vegetation to protect or shade their young.<ref name="car">Carlile, N., Proiddel, D., Zino, F., Natividad, C. & Wingate, D.B. (2003) "A review of four successful recovery programmes for threatened sub-tropical petrels" ''Marine Ornithology'' '''31''': 185–192</ref> Disturbance of breeding colonies by humans is often a problem as well—visitors, even well-meaning [[tourism|tourists]], can flush brooding adults off a colony leaving chicks and eggs vulnerable to predators.
 
[[Berkas:Oiledcrestedauklet.jpeg|thumb|left|This [[Crested Auklet]] was oiled in Alaska during the M/V [[Selendang Ayu]] spill of 2004.]]
The build-up of [[toxin]]s and [[pollution|pollutants]] in seabirds is also a concern. Seabirds, being apex predators, suffered from the ravages of [[DDT]] until it was banned; among other effects, DDT was implicated in embryo development problems and the skewed sex ratio of [[Western Gull]]s in southern California.<ref>Fry, D. & Toone, C. (1981) "DDT-induced feminization of gull embryos" ''Science'' '''213'''(4510): 922–924</ref> [[Oil spill]]s are also a threat to seabird species, as both a toxin and because the feathers of the birds become saturated by the oil, causing them to lose their waterproofing.<ref>Dunnet, G., Crisp, D., Conan, G., Bourne, W. (1982) "Oil Pollution and Seabird Populations [and Discussion]" ''Philosophical Transactions of the Royal Society of London. B'' '''297'''(1087): 413–427</ref> Oil pollution threatens species with restricted ranges or already depressed populations.
 
===Conservation===
The threats faced by seabirds have not gone unnoticed by scientists or the [[conservation movement]]. As early as 1903, U.S. President [[Theodore Roosevelt]] was convinced of the need to declare [[Pelican Island National Wildlife Refuge|Pelican Island]] in [[Florida]] a [[National Wildlife Refuge]] to protect the bird colonies (including the nesting [[Brown Pelican]]s),<ref>USFWS Pelican Island National Wildlife Refuge [http://www.fws.gov/pelicanisland/history.html History of Pelican Island] Retrieved September 2, 2006</ref> and in 1909 he protected the [[Farallon Islands]]. Today many important seabird colonies are given some measure of protection, from [[Heron Island, Australia|Heron Island]] in [[Australia]] to Triangle Island in [[British Columbia]].
 
[[Island restoration]] techniques, pioneered by [[New Zealand]], enable the removal of exotic invaders from increasingly large islands. Feral cats have been removed from [[Ascension Island]], [[Arctic Fox]]es from many islands in the [[Aleutian Islands]],<ref>Williams, J.C., Byrd G.V.& Konyukhov, N.B. (2003) "Whiskered Auklets ''Aethia pygmaea'', foxes, humans and how to right a wrong." ''Marine Ornithology'' '''31''': 175–180 [http://www.marineornithology.org/PDF/31_2/31_2_175-180.pdf]</ref> and rats from [[Campbell Island, New Zealand|Campbell Island]]. The removal of these introduced species has led to increases in numbers of species under pressure and even the return of extirpated ones. After the removal of cats from Ascension Island, seabirds began to nest there again for the first time in over a hundred years.<ref>BirdLife International (2005) [http://www.birdlife.org/news/news/2005/07/ascension.html Stamps celebrate seabird return]. Retrieved August 12, 2006</ref>
 
Seabird mortality caused by long-line fisheries can be greatly reduced by techniques such as setting long-line bait at night, dying the bait blue, setting the bait underwater, increasing the amount of weight on lines and by using bird scarers,<ref>Food and Agriculture Organisation (1999) "The incidental catch of seabirds by longline fisheries: worldwide review and technical guidelines for mitigation. FAO Fisheries Circular No.937. Food and Agriculture Organization of the United Nations, Rome. [http://www.fao.org/documents/show_cdr.asp?url_file=/DOCREP/005/W9817E/W9817E00.HTM]</ref> and their deployment is increasingly required by many national fishing fleets. The international ban on the use of [[drift net]]s has also helped reduce the mortality of seabirds and other marine wildlife.
 
One of the Millennium Projects in the UK was the [[Scottish Seabird Centre]], near the important bird sanctuaries on [[Bass Rock]], [[Fidra]] and the surrounding islands. The area is home to huge colonies of gannets, [[puffin]]s, skuas and other seabirds. The centre allows visitors to watch live video from the islands as well as learn about the threats the birds face and how we can protect them, and has helped to significantly raise the profile of seabird conservation in the UK. Seabird tourism can provide income for coastal communities as well as raise the profile of seabird conservation. For example, the [[Northern Royal Albatross]] colony at [[Taiaroa Head]] in New Zealand attracts 40,000 visitors a year.<ref name = "Brooke"/>
 
The plight of albatross and large seabirds, as well as other marine creatures, being taken as bycatch by long-line fisheries, has been addressed by a large number of [[non-governmental organization]]s (including [[BirdLife International]], the American Bird Conservancy, and the [[Royal Society for the Protection of Birds]]). This led to the [[Agreement on the Conservation of Albatrosses and Petrels]], a legally binding treaty designed to protect these threatened species, which has been ratified by eleven countries as of 2008 (namely Argentina, Australia, Chile, [[Ecuador]], [[France]], New Zealand, Norway, [[Peru]], [[South Africa]], [[Spain]], and the [[United Kingdom]]).<ref>Australian Antarctic Division [http://www.acap.aq/ Agreement on the Conservation of Albatrosses and Petrels Site] Retrieved April 8, 2008</ref>
 
===Role in culture===
[[Berkas:Pelican in its piety.jpg|thumb|right|Depiction of a pelican with chicks on a stained glass window, Saint Mark's Church, [[Gillingham, Kent|Gillingham]], [[Kent]].]]
Many seabirds are little studied and poorly known, due to living far out to sea and breeding in isolated colonies. However, some seabirds, particularly, the albatrosses and gulls, have broken into popular consciousness. The albatrosses have been described as "the most legendary of birds",<ref name="delhoyo">Carboneras, C. (1992) "Family Diomedeidae (Albatrosses)" in ''Handbook of Birds of the World'' Vol 1. Barcelona:Lynx Edicions, ISBN 84-87334-10-5</ref> and have a variety of [[mythology|myths]] and [[legend]]s associated with them, and today it is widely considered [[luck|unlucky]] to harm them, although the notion that sailors believed that is a [[urban legend|myth]]<ref name = "Brit">Cocker, M., & Mabey, R., (2005) ''Birds Britannica'' London:Chatto & Windus, ISBN 0-7011-6907-9</ref> which derives from [[Samuel Taylor Coleridge]]'s famous [[poem]], "[[The Rime of the Ancient Mariner]]", in which a sailor is punished for killing an albatross by having to wear its corpse around his neck.
 
''Instead of the Cross the Albatross''<br>
''About my neck was hung''
 
Sailors did, however, consider it unlucky to touch a [[storm-petrel]], especially one that has landed on the ship.<ref name="delhoyo">Carboneras, C. (1992) "Family Hydrobatidae (Storm-petrels)" in ''Handbook of Birds of the World'' Vol 1. Barcelona:Lynx Edicions, ISBN 84-87334-10-5</ref>
 
Gulls are one of the most commonly seen seabirds, given their use of human-made [[habitat (ecology)|habitats]] (such as cities and [[landfill|dumps]]) and their often fearless nature. They therefore also have made it into the popular consciousness – they have been used [[metaphor]]ically, as in ''[[Jonathan Livingston Seagull]]'' by [[Richard Bach]], or to denote a closeness to the sea, such as their use in ''[[The Lord of the Rings]]''{{spaced ndash}} both in the [[insignia]] of [[Gondor]] and therefore [[Númenor]] (used in the design of the films), and to call [[Legolas]] to (and across) the sea. Other species have also made an impact; [[pelican]]s have long been associated with mercy and [[altruism]] because of an early Western [[Christianity|Christian]] myth that they split open their breast to feed their starving chicks.<ref name="elliot"/>
 
==Seabird families==
The following are the groups of birds normally classed as seabirds.
 
'''[[Sphenisciformes]]''' (Antarctic and southern waters; 16 species)
* Spheniscidae [[penguin]]s
 
'''[[Procellariiformes]]''' (Tubenoses: pan-oceanic and pelagic; 93 species)
* Diomedeidae [[albatross]]es
* Procellariidae [[fulmar]]s, [[prion (bird)|prions]], [[shearwater]]s, [[gadfly petrel|gadfly]] and other [[petrel]]s
* Pelacanoididae [[diving petrel]]s
* Hydrobatidae [[storm petrel]]s
 
'''[[Pelecaniformes]]''' (Worldwide; 57 species)
* Pelecanidae [[pelican]]s
* Sulidae [[gannet]]s and [[booby|boobies]]
* Phalacrocoracidae [[cormorant]]s
* Fregatidae [[frigatebird]]s
 
* Phaethontidae [[tropicbird]]s
 
[[Charadriiformes]] (Worldwide; 305 species, but only the families listed are classed as seabirds.)
* Stercorariidae [[skua]]s
* Laridae [[gull]]s
* Sternidae [[tern]]s
* Rhynchopidae [[skimmer]]s
* Alcidae [[auk]]s
 
For an alternative taxonomy of these groups, see also [[Sibley-Ahlquist taxonomy]].
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== Referensi ==
{{Reflist|2}}
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