Burung laut: Perbedaan antara revisi

{{terjemah|Inggris}}

'''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]].

 

== 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>

 

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>

 

[[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]].

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.

 

====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.

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.

 

 

====Pursuit diving====

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.

 

 

====Kleptoparasitism, scavenging and predation====

" ''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"/>

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"/>

 

:''See also [[Unusual Seabird Breeding Behavior]]

 

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.

 

 

===Migration===

 

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.

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"/>

 

 

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.

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.

 

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.

 

 

===Role in culture===

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.