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114-637: See text . The skuas / ˈ s k juː ə / are a group of predatory seabirds with seven species forming the genus Stercorarius , the only genus in the family Stercorariidae . The three smaller skuas, the Arctic skua , the long-tailed skua , and the pomarine skua , are called jaegers in North American English . The English word "skua" comes from the Faroese name for the great skua , skúgvur [ˈskɪkvʊɹ] , with
228-443: A grey heron . On the breeding grounds, the three, more slender northern breeding species commonly eat lemmings . Those species that breed in the southern oceans largely feed on fish that can be caught near their colonies. The eggs and chicks of other seabirds, primarily penguins , are an important food source for most skua species during the nesting season. In the southern oceans and Antarctica region, some skua species (especially
342-447: A murre colony. In most seabird colonies, several different species will nest on the same colony, often exhibiting some niche separation . Seabirds can nest in trees (if any are available), on the ground (with or without nests ), on cliffs, in burrows under the ground and in rocky crevices. Competition can be strong both within species and between species, with aggressive species such as sooty terns pushing less dominant species out of
456-401: A wreck . Seabirds have had a long association with both fisheries and sailors , and both have drawn benefits and disadvantages from the relationship. Fishermen have traditionally used seabirds as indicators of both fish shoals , underwater banks that might indicate fish stocks, and of potential landfall. In fact, the known association of seabirds with land was instrumental in allowing
570-450: A behaviour seen in other animal species, such as elephants, wolves, and the fathead minnow . Lasting between 22 and 26 days, incubation begins after the first egg is laid but is not continuous until after the second egg is laid, meaning that the first two chicks hatch at about the same time, and the third some time later. Young chicks are brooded by their parents for about one or two weeks, and often at least one parent stays behind to guard
684-618: A clade, the Aequornithes either became seabirds in a single transition in the Cretaceous or some lineages such as pelicans and frigatebirds adapted to sea living independently from freshwater-dwelling ancestors. In the Paleogene both pterosaurs and marine reptiles became extinct, allowing seabirds to expand ecologically. These post-extinction seas were dominated by early Procellariidae , giant penguins and two extinct families ,
798-543: A colony. Eggers from 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. 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 of Stewart Island / Rakiura continue to harvest
912-486: A fashion similar to grebes and loons (using its feet to move underwater) but had a beak filled with sharp teeth. Flying Cretaceous seabirds do not exceed wingspans of two meters; any sizes were taken by piscivorous pterosaurs . While Hesperornis is not thought to have left descendants, the earliest modern seabirds also occurred in the Cretaceous, with a species called Tytthostonyx glauconiticus , which has features suggestive of Procellariiformes and Fregatidae. As
1026-495: A few species do live on islands such as the Galapagos and New Caledonia . Many species breed in coastal colonies, with a preference for islands, and one species, the grey gull , breeds in the interior of dry deserts far from water. Considerable variety exists in the family and species may breed and feed in marine, freshwater, or terrestrial habitats. Most gull species are migratory , with birds moving to warmer habitats during
1140-528: A fleshy cere above the upper mandible. The skuas are strong, acrobatic fliers. They are generally aggressive in disposition. Potential predators approaching their nests will be quickly attacked by the parent birds, which usually target the heads of intruders – a practice known as ' divebombing '. The genus Stercorarius was introduced by the French zoologist Mathurin Jacques Brisson in 1760 with
1254-451: A great deal of time in their young. Most species nest in colonies , varying in size from a few dozen birds to millions. Many species are famous for undertaking long annual migrations , crossing the equator or circumnavigating the Earth in some cases. They feed both at the ocean's surface and below it, and even on each other. Seabirds can be highly pelagic , coastal, or in some cases spend
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#17327804221561368-498: A higher level of synchronisation in larger colonies. The eggs of gulls are usually dark tan to brown or dark olive with dark splotches and scrawl markings, and they are well camouflaged. Both sexes incubate the eggs; incubation bouts last between one and four hours during the day, and one parent incubates through the night. Research on various bird species, including gulls, suggests that females form pair bonds with other females to obtain alloparental care for their dependent offspring,
1482-971: A large number of non-governmental organizations (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 thirteen countries as of 2021 (Argentina, Australia, Brazil, Chile, Ecuador, France, New Zealand, Norway, Peru, South Africa, Spain, Uruguay, United Kingdom). Many seabirds are little studied and poorly known because they live far out at sea and breed in isolated colonies. Some seabirds, particularly
1596-570: A lineage— Eurypygimorphae —that is a sister group to the Aequornithes. Seabirds, by virtue of living in a geologically depositional environment (that is, in the sea where sediments are readily laid down), are well represented in the fossil record. They are first known to occur in the Cretaceous period, the earliest being the Hesperornithiformes , like Hesperornis regalis , a flightless loon-like seabird that could dive in
1710-587: A million birds have been recorded, both in the tropics (such as Kiritimati in the 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
1824-534: A mixture of both natural prey and human refuse. The gulls relied substantially on the Henslow's swimming crab ( Polybius henslowii ). Yet, in times when local prey availability is low, the gulls shift to human-related food. These temporal shifts from a marine to terrestrial prey highlight the resilience adult gulls have and their ability to keep chick condition consistent. Human disturbance has also shown to have an effect on gull breeding, in which hatching failure
1938-569: A number of years after the break-up. Gulls also display high levels of site fidelity , returning to the same colony after breeding there once and even usually breeding at the same location within that colony. Gull colonies can vary from just a few pairs to over a hundred thousand pairs, and may be exclusive to that gull species or shared with other seabird species. A few species nest singly, and single pairs of band-tailed gulls may breed in colonies of other bird species. Within colonies, gull pairs are territorial , defending an area of varying size around
2052-693: A part of the year away from the sea entirely. Seabirds and humans have a long history together: They have provided food to hunters , guided fishermen to fishing stocks, and led sailors to land. Many species are currently threatened by human activities such as oil spills , nets, climate change and severe weather. Conservation efforts include the establishment of wildlife refuges and adjustments to fishing techniques. There exists no single definition of which groups, families and species are seabirds, and most definitions are in some way arbitrary. Elizabeth Shreiber and Joanna Burger, two seabird scientists, said, "The one common characteristic that all seabirds share
2166-414: A place for returning mates to reunite, and reduces the costs of prospecting for a new site. 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 albatrosses found that the average distance between hatching site and the site where a bird established its own territory
2280-410: A red spot for the larger white-headed species and red, dark red or black in the smaller species. Gulls are a generalist species that can thrive in various environments and survive on a widely varied diet. They are the least specialised of all the seabirds, and their morphology allows for equal adeptness in swimming, flying, and walking. They are more adept walking on land than most other seabirds, and
2394-438: 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. 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 among birds in having a strong sense of smell , which is used to find widely distributed food in
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#17327804221562508-461: A smaller layer of air (compared to other diving birds) but otherwise soak up water. 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. A few species sport colourful plumes (such as
2622-575: 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. 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 albatrosses are known to still exist). Seabirds are also thought to suffer when overfishing occurs. Changes to
2736-560: A suitable surface on which to drop shells, and apparently a learned component to the task exists, as older birds are more successful than younger ones. While overall feeding success is a function of age, the diversity in both prey and feeding methods is not. The time taken to learn foraging skills may explain the delayed maturation in gulls. Gulls have only a limited ability to dive below the water to feed on deeper prey. To obtain prey from deeper down, many species of gulls feed in association with other animals, where marine hunters drive prey to
2850-403: A vast ocean, and help distinguish familiar nest odours from unfamiliar ones. Salt glands are used by seabirds to deal with the salt they ingest by drinking and feeding (particularly on crustaceans ), and to help them osmoregulate . The excretions from these glands (which are positioned in the head of the birds, emerging from the nasal cavity ) are almost pure sodium chloride . With
2964-400: A very variable prey source); this may be a reason why it arises more frequently in seabirds. 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
3078-458: A year, unless they lose the first (with a few exceptions, like the Cassin's auklet ), and many species (like the tubenoses and sulids ) will only lay one egg a year. 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. The frigatebirds have
3192-427: Is a layperson's term and is not used by most ornithologists and biologists. The name is used informally to refer to a common local species (or all gulls in general) and has no fixed taxonomic meaning. In common usage, gull-like seabirds that are not technically gulls (e.g. albatrosses , fulmars , terns , and skuas ) may also be referred to as 'seagulls' by the layperson. The American Ornithologists' Union combines
3306-516: Is a list of the 54 gull species , presented in taxonomic sequence . The Laridae are known from not-yet-published fossil evidence since the Early Oligocene , some 30–33 million years ago. Three gull-like species were described by Alphonse Milne-Edwards from the early Miocene of Saint-Gérand-le-Puy, France. A fossil gull from the Middle to Late Miocene of Cherry County, Nebraska , US,
3420-468: Is a single-prey specialist, and no gull species forages using only a single method. The type of food depends on circumstances, and terrestrial prey such as seeds, fruit, and earthworms are more common during the breeding season while marine prey is more common in the nonbreeding season when birds spend more time on large bodies of water. In addition to taking a wide range of prey, gulls display great versatility in how they obtain prey. Prey can be obtained in
3534-401: Is an important part of the pair-bonding process. Most gull nests are mats of herbaceous matter with a central nest cup. Nests are usually built on the ground, but a few species establish their nests on cliffs (the usual preference for kittiwakes), and some choose to nest in trees and high places (e.g. Bonaparte's gulls ). Species that nest in marshes need to construct a nesting platform to keep
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3648-423: Is darker varies from pale grey to black. A few species vary in this, the ivory gull is entirely white, and some like the lava gull and Heermann's gull have partly or entirely grey bodies. The wingtips of most species are black, which improves their resistance to wear and tear, usually with a diagnostic pattern of white markings. The head of a gull may be covered by a dark hood or be entirely white. The plumage of
3762-419: Is directly proportional to the amount of disturbance in a given plot. Certain gull breeds have been known to feast on the eyeballs of baby seals, and directly pilfer milk from the elephant seal 's teat. Gulls are monogamous and colonial breeders that display mate fidelity which normally lasts for the life of the pair. Divorce of mated pairs does occur, but it apparently has a social cost that persists for
3876-407: 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. Gannets , boobies , tropicbirds , some terns, and brown pelicans all engage in plunge diving, taking fast-moving prey by diving into the water from the flight. Plunge diving allows birds to use the energy from the momentum of
3990-642: Is inconclusive. Some plunge divers (as well as some surface feeders) are dependent on dolphins and tuna to push shoaling fish up towards the surface. This catch-all category refers to other seabird strategies that involve the next trophic level up. Kleptoparasites are seabirds that make a part of their living stealing food of other seabirds. Most famously, frigatebirds and skuas engage in this behaviour, although gulls, terns and other species will steal food opportunistically. The nocturnal nesting behaviour of some seabirds has been interpreted as arising due to pressure from this aerial piracy. Kleptoparasitism
4104-545: Is not thought to play a significant part of the diet of any species, and is instead a supplement to food obtained by hunting. A study of great frigatebirds stealing from masked boobies estimated that the frigatebirds could at most obtain 40% of the food they needed, and on average obtained only 5%. Many species of gull will feed on seabird and sea mammal carrion when the opportunity arises, as will giant petrels . Some species of albatross also engage in scavenging: an analysis of regurgitated squid beaks has shown that many of
4218-402: Is often a problem as well—visitors, even well-meaning tourists, can flush brooding adults off a colony, leaving chicks and eggs vulnerable to predators. The build-up of toxins and pollutants in seabirds is also a concern. Seabirds, being apex predators , suffered from the ravages of the insecticide DDT until it was banned; DDT was implicated, for example, in embryo development problems and
4332-464: Is punished for killing an albatross by having to wear its corpse around his neck. Sailors did, however, consider it unlucky to touch a storm petrel, especially one that landed on the ship. Gull 11, see below Gulls , or colloquially seagulls , are seabirds of the family Laridae in the suborder Lari . They are most closely related to terns and skimmers , distantly related to auks , and even more distantly related to waders . Until
4446-464: Is questionable. Before the 21st century, most gulls were placed in the genus Larus , but this arrangement is now known to be polyphyletic , leading to the resurrection of the genera Ichthyaetus , Chroicocephalus , Leucophaeus , Saundersilarus , and Hydrocoloeus . Some English names refer to species complexes within the group: In common usage, members of various gull species are often referred to as 'sea gulls' or 'seagulls'; however, this
4560-489: Is some evidence of this, the effects of seabirds are considered smaller than that of marine mammals and predatory fish (like tuna ). 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. This can have other impacts; for example,
4674-783: Is that they feed in saltwater ; but, as seems to be true with any statement in biology, some do not." However, by convention all of the Sphenisciformes (penguins) and Procellariiformes ( albatrosses and petrels ), all of the Suliformes ( gannets and cormorants ) except the darters , and some of the Charadriiformes (the gulls , skuas , terns , auks and skimmers ) are classified as seabirds. The phalaropes are usually included as well, since although they are waders ("shorebirds" in North America), two of
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4788-589: 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. Prions have special bills with filters called lamellae to filter out plankton from mouthfuls of water, and many albatrosses and petrels have hooked bills to snatch fast-moving prey. On
4902-448: Is the deepest diver of the shearwaters, having been recorded diving below 70 metres (230 ft). Some albatross species are also capable of limited diving, with light-mantled sooty albatrosses holding the record at 12 metres (40 ft). 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
5016-715: The Pelagornithidae and the Plotopteridae (a group of large seabirds that looked like the penguins). 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 . Within the Charadriiformes, the gulls and allies ( Lari ) became seabirds in the late Eocene, and then waders in
5130-703: The Polynesians to locate tiny landmasses in the Pacific. Seabirds have provided food for fishermen away from home, as well as bait. Famously, tethered cormorants 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 , although long-lining fisheries also have to deal with bait stealing. There have been claims of prey depletion by seabirds of fishery stocks, and while there
5244-577: The South Pole . Outside the breeding season, skuas take fish, offal , and carrion . Many practice kleptoparasitism , which comprises up to 95% of the feeding methods of wintering skuas, by chasing gulls, terns and other seabirds to steal their catches, regardless of the size of the species attacked (up to three times heavier than the attacking skua). Larger species, such as the great skua , regularly kill and eat adult seabirds, such as puffins and gulls and have been observed killing birds as large as
5358-800: The Sternidae , Stercorariidae , and Rhynchopidae as subfamilies in the family Laridae, but early 21st-century research shows this to be incorrect. A molecular phylogenetic study published in 2022 found the following relationships between the genera, including the most recent generic change: the placement of Saunders's gull in its own genus Saundersilarus . Creagrus – swallow-tailed gull Hydrocoloeus – little gull Rhodostethia – Ross's gull Rissa – kittiwakes (2 species) Xema – Sabine's gull Pagophila – ivory gull Saundersilarus – Saunders's gull Chroicocephalus – (10 species) Leucophaeus – (5 species) Ichthyaetus – (6 species) Larus – (24 species) This
5472-531: The kittiwakes and Sabine's gull . The large species take up to four years to attain full adult plumage, but two years is typical for small gulls. Large white-headed gulls are usually long-lived birds, with a maximum age of 49 years recorded for the herring gull . Gulls nest in large, densely packed, noisy colonies. They lay two or three speckled eggs in nests composed of vegetation. The young are precocial , born with dark mottled down and mobile upon hatching. Gulls are resourceful, inquisitive, and intelligent,
5586-455: The marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution , as the same environmental problems and feeding niches have resulted in similar adaptations. The first seabirds evolved in the Cretaceous period , and modern seabird families emerged in the Paleogene . Seabirds generally live longer, breed later and have fewer young than other birds, but they invest
5700-677: The millinery trade reached industrial levels. Muttonbirding (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. 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
5814-465: The parasitic jaeger ( Stercorarius parasiticus ) as the type species . Skuas are related to gulls , waders , auks , and skimmers . In the three smaller species, all nesting exclusively in the Holarctic , breeding adults have the two central tail feathers obviously elongated, and at least some adults have white on the underparts and pale yellow on the neck. These characteristics are not shared by
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#17327804221565928-419: The razorbill (an Atlantic auk) requires 64% more energy to fly than a petrel of equivalent size. Many shearwaters are intermediate between the two, having longer wings than typical wing-propelled divers but heavier wing loadings than the other surface-feeding procellariids , leaving them capable of diving to considerable depths while still being efficient long-distance travellers. The short-tailed shearwater
6042-481: The shearwaters 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. 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. Another seabird family that does not land while feeding
6156-507: The south polar skua ) will readily scavenge carcasses at breeding colonies of both penguins and pinnipeds . Skuas will also kill live penguin chicks and sick or injured adult penguins. In these areas, the skuas will often forfeit their catches to the considerably larger and very aggressive giant petrels . Skuas have also been observed to directly pilfer milk from the elephant seal 's teats. Skuas are medium to large birds , typically with grey or brown plumage, often with white markings on
6270-512: The 21st century, most gulls were placed in the genus Larus , but that arrangement is now considered polyphyletic , leading to the resurrection of several genera. An older name for gulls is mews ; this still exists in certain regional English dialects and is cognate with German Möwe , Danish måge , Swedish mås , Dutch meeuw , Norwegian måke/måse , and French mouette . Typically medium to large in size, gulls are usually grey or white, often with black markings on
6384-526: The Antarctic mainland, are unlikely to find anything to eat around their breeding sites. The marbled murrelet nests inland in old growth forest , seeking huge conifers with large branches to nest on. Other species, such as the California gull , nest and feed inland on lakes, and then move to the coasts in the winter. Some cormorant, pelican , gull and tern species have individuals that never visit
6498-642: 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 64,000 kilometres (40,000 mi). 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
6612-726: 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 terns , 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 . The sooty shearwater undertakes an annual migration cycle that rivals that of
6726-556: 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, puffins , 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
6840-480: The UK. Seabird tourism can provide income for coastal communities as well as raise the profile of seabird conservation, although it needs to be managed to ensure it does not harm the colonies and nesting birds. For example, the northern royal albatross colony at Taiaroa Head in New Zealand attracts 40,000 visitors a year. 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
6954-420: The air, on water, or on land. In the air, a number of hooded species are able to hawk insects on the wing; larger species perform this feat more rarely. Gulls on the wing also snatch items both off water and off the ground, and over water they also plunge-dive to catch prey. Again, smaller species are more manoeuvrable and better able to hover-dip fish from the air. Dipping is also common when birds are sitting on
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#17327804221567068-467: The albatrosses and gulls, are more well known to humans. The albatross has been described as "the most legendary of birds", and have a variety of myths and legends associated with them. While it is widely considered unlucky to harm them, the notion that sailors believed that is a myth that derives from Samuel Taylor Coleridge 's famous poem, " The Rime of the Ancient Mariner ", in which a sailor
7182-400: The attention of predators , principally other birds, and many species attend their colonies nocturnally to avoid predation. Birds from different colonies often forage in different areas to avoid competition. Like many birds, seabirds often 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
7296-454: The bird is young. 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. Other species, such as some of the storm petrels, diving petrels and cormorants, never disperse at all, staying near their breeding colonies year round. While
7410-472: The black-backed gull) was heavily impacted by human fishing discards and fishing ports. Looking further at environmental drivers that structure bird habitat and distribution are human and climate impacts. Looking at waterbird distribution in wetlands, changes in salinity, water depth, water body isolation and hydroperiod altered bird community structure in both a species and guild specific way. Gulls in particular had high associations with salinity levels, being
7524-486: The chicks of the sooty shearwater as they have done for centuries, using traditional stewardship, kaitiakitanga , to manage the harvest, but now also work with the University of Otago in studying the populations. In Greenland , however, uncontrolled hunting is pushing many species into steep decline. Other human factors have led to declines and even extinctions in seabird populations and species. Of these, perhaps
7638-533: The chicks until they fledge . Although the chicks are fed by both parents, early on in the rearing period the male does most of the feeding and the female most of the brooding and guarding. The family Laridae was introduced (as Laridia) by the French polymath Constantine Samuel Rafinesque in 1815. The taxonomy of gulls is confused by their widespread distribution zones of hybridisation leading to gene flow . Some have traditionally been considered ring species , but research has suggested that this assumption
7752-411: The coasts near their breeding sites. A big influence on non-breeding gull distribution are food patches. Human fisheries especially have an impact since they often provide an abundant and predictable food resource. Looking at two species of gulls dependent on human fisheries, Audouin's gull ( Ichthyaetus audouinii ) and lesser black-backed gulls ( Larus fuscus) , their breeding distributions (especially
7866-453: 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 480 kilometres (300 mi) inland on
7980-451: The disease have scarred digestive tracts from ingesting plastic waste . "When birds ingest small pieces of plastic, they found, it inflames the digestive tract. Over time, the persistent inflammation causes tissues to become scarred and disfigured, affecting digestion, growth and survival." The threats faced by seabirds have not gone unnoticed by scientists or the conservation movement . As early as 1903, U.S. President Theodore Roosevelt
8094-456: The dive to combat natural buoyancy (caused by air trapped in plumage), and thus uses less energy than the dedicated pursuit divers, allowing them to utilise more widely distributed food resources, for example, in impoverished 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,
8208-413: The earliest instances known is in southern Chile, where archaeological excavations in middens has shown hunting of albatrosses, cormorants and shearwaters from 5000 BP. 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
8322-404: The exception of the cormorants 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
8436-400: The exceptions being Sabine's gull and swallow-tailed gulls , which have forked tails, and Ross's gull , which has a wedge-shaped tail. Gulls have moderately long legs, especially when compared to the similar terns, with fully webbed feet. The bill is generally heavy and slightly hooked, with the larger species having stouter bills than the smaller species. The bill colour is often yellow with
8550-676: The feathers resist abrasion. Seabirds evolved to exploit different food resources in the world's seas and oceans, and to a great extent, their physiology and behaviour have been shaped by their 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
8664-475: The first time in over a hundred years. 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, and their deployment is increasingly required by many national fishing fleets. One of the Millennium Projects in
8778-478: The frequency of breeding failures due to unfavourable marine conditions, and the relative lack of predation compared to that of land-living birds. 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 monogamous . Many species, such as gulls, auks and penguins, retain
8892-549: The head or wings. They normally have harsh wailing or squawking calls; stout, longish bills; and webbed feet. Most gulls are ground-nesting piscivores or carnivores which take live food or scavenge opportunistically, particularly the Larus species. Live food often includes crustaceans , molluscs , fish and small birds. Gulls have unhinging jaws that provide the flexibility to consume large prey. Gulls are typically coastal or inland species, rarely venturing far out to sea, except for
9006-422: The head varies by breeding season; in nonbreeding dark-hooded gulls, the hood is lost, sometimes leaving a single spot behind the eye, and in white-headed gulls, nonbreeding heads may have streaking. The gulls have a worldwide cosmopolitan distribution . They breed on every continent, including the margins of Antarctica , and are found in the high Arctic as well. They are less common on tropical islands, although
9120-486: The island of Skúvoy renowned for its colony of that bird. The general Faroese term for skuas is kjógvi [ˈtʃɛkvɪ] . The word "jaeger" or Jäger is German for "hunter". The genus name Stercorarius is Latin and means "of dung"; the food disgorged by other birds when pursued by skuas was once thought to be excrement. Skuas nest on the ground in temperate , Antarctic , and Arctic regions , and are long-distance migrants . They have even been sighted at
9234-607: The larger species in particular, demonstrating complex methods of communication and a highly developed social structure. For example, many gull colonies display mobbing behaviour, attacking and harassing predators and other intruders. Certain species, such as the herring gull, have exhibited tool-use behaviour, for example using pieces of bread as bait with which to catch goldfish . Many species of gulls have learned to coexist successfully with humans and thrive in human habitats. Others rely on kleptoparasitism to get their food. Gulls have been observed preying on live whales, landing on
9348-652: The larger species, all native to the Southern Hemisphere except for the great skua. Therefore, the skuas are often split into two genera, with only the smaller species retained in Stercorarius , and the large species placed in Catharacta . However, based on genetics , behavior, and feather lice , the overall relationship among the species is best expressed by placing all in a single genus. The pomarine and great skuas' mitochondrial DNA (inherited from
9462-468: The longest period of parental care of any bird except a few raptors and the southern ground hornbill , with each chick fledging after four to six months and continued assistance after that for up to fourteen months. 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),
9576-703: The main environmental predictor for waterbird assemblage. Charadriiform birds drink salt water, as well as fresh water, as they possess exocrine glands located in supraorbital grooves of the skull by which salt can be excreted through the nostrils to assist the kidneys in maintaining electrolyte balance. Gulls are highly adaptable feeders that opportunistically take a wide range of prey. The food taken by gulls includes fish and marine and freshwater invertebrates, both alive and already dead; terrestrial arthropods and invertebrates such as insects and earthworms; rodents, eggs, carrion, offal , reptiles, amphibians, seeds, fruit, human refuse, and even other birds. No gull species
9690-408: The marine ecosystems caused by dredging, which alters the biodiversity of the seafloor, can also have a negative impact. The hunting of seabirds and the collecting of seabird eggs have contributed to the declines of many species, and the extinction of several, including the great auk and the spectacled cormorant . Seabirds have been hunted for food by coastal peoples throughout history—one of
9804-580: The middle Miocene ( Langhian ). 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; subsequently, the spread of marine mammals seems to have prevented seabirds from reaching their erstwhile diversity. Seabirds have made numerous adaptations to living on and feeding in
9918-490: The most desirable nesting spaces. 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. 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. This increases breeding success, provides
10032-552: The most serious are introduced species . Seabirds, breeding predominantly on small isolated islands, are vulnerable to predators because they have lost many behaviours associated with defence from predators. Feral cats can take seabirds as large as albatrosses, and many introduced rodents, such as the Pacific rat , take eggs hidden in burrows. Introduced goats, cattle, rabbits and other herbivores can create problems, particularly when species need vegetation to protect or shade their young. The disturbance of breeding colonies by humans
10146-581: The mother) is in fact more closely related to each other than it is to either Arctic or long-tailed skuas, or to the Southern Hemisphere species. Thus, hybridization must have played a considerable role in the evolution of the diversity of Northern Hemisphere skuas. The genus contains seven species: [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] Seabird Seabirds (also known as marine birds ) are birds that are adapted to life within
10260-463: The nest dry, particularly species that nest in tidal marshes . Both sexes gather nesting material and build the nest, but the division of labour is not always exactly equal. In coastal towns, many gulls nest on rooftops and can be observed by nearby human residents. Clutch size is typically three eggs, although some of the smaller gulls only lay two, and the swallow-tailed gull produces a single egg. Birds synchronise their laying within colonies, with
10374-677: The nesting site from others of their species. This area can be as large as a 5-metre radius around the nest in the herring gull to just a tiny area of cliff ledge in the kittiwakes . Most gulls breed once a year and have predictable breeding seasons lasting for three to five months. Gulls begin to assemble around the colony for a few weeks prior to occupying it. Existing pairs re-establish their pair-bonds , and unpaired birds begin courting. Pairs then move back into their territories, and new males establish new territories and attempt to court females. Gulls defend their territories from rivals of both sexes using calls and aerial attacks. Nest building
10488-577: The northwest coast of Spain revealed a shift from a sardine to crustacean-based diet. This shift was linked to higher fishing efficiency and thus overall fish stock depletion. Lastly, closure of nearby open-air landfills limited food availability for the gulls, furthering creating a stress on their shift in diet. Between the years of 1974–1994, yellow-legged gull populations in Berlenga Island, Portugal, increased from 2600 to 44,698 individuals. Analyzing both adult and chick remains, researchers found
10602-428: The ocean lead to decreased availability of food and colonies are more often flooded as a consequence of sea level rise and extreme rainfall events. Heat stress from extreme temperatures is an additional threat. Some seabirds have used changing wind patterns to forage further and more efficiently. In 2023, plasticosis , a new disease caused solely by plastics, was discovered in seabirds. The birds identified as having
10716-841: The other hand, most gulls are versatile and opportunistic feeders who will eat a wide variety of prey, both at sea and on land. 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 propulsion is provided by wings (as used by penguins, auks, diving petrels and some other species of petrel) or feet (as used by cormorants, grebes , loons and several types of fish-eating ducks ). Wing-propelled divers are generally faster than foot-propelled divers. 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,
10830-503: The removal of exotic invaders from increasingly large islands. Feral cats have been removed from Ascension Island , Arctic foxes from many islands in the Aleutian Islands , and rats from 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
10944-465: The same mate for several seasons, and many petrel species mate for life. Albatrosses and procellariids , 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. Ninety-five percent of seabirds are colonial, and seabird colonies are among the largest bird colonies in the world, providing one of Earth's great wildlife spectacles. Colonies of over
11058-653: The sea at all, spending their lives on lakes, rivers, swamps and, in the case of some of the gulls, cities and agricultural land. In these cases, it is thought that these terrestrial or freshwater birds evolved from marine ancestors. Some seabirds, principally those that nest in tundra , as skuas and phalaropes do, will migrate over land as well. The more marine species, such as petrels, auks and gannets , 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 storms , an event known as
11172-507: The sea's edge (coast), but are also not treated as seabirds. Sea eagles and other fish-eating birds of prey are also typically excluded, however tied to marine environments they may be. German ornithologist Gerald Mayr defined the "core waterbird" clade Aequornithes in 2010. This lineage gives rise to the Gaviiformes , Sphenisciformes , Procellariiformes, Ciconiiformes , Suliformes and Pelecaniformes . The tropicbirds are part of
11286-407: The sea. Wing morphology has been shaped by the niche an individual species or family has evolved , so that looking at a wing's shape and 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. Species such as the wandering albatross , which forage over huge areas of sea, have
11400-416: The skewed sex ratio of western gulls in southern California. Oil spills are also a threat to seabirds: the oil is toxic, and bird feathers become saturated by the oil, causing them to lose their waterproofing. Oil pollution in particular threatens species with restricted ranges or already depressed populations. Climate change mainly affect seabirds via changes to their habitat : various processes in
11514-432: The skills of plunge-diving take several years to fully develop—once mature, they can dive from 20 m (66 ft) above the water's surface, shifting the body before impact to avoid injury. 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. While they are the dominant guild in the tropics, the link between plunge diving and water clarity
11628-399: The smaller gulls tend to be more manoeuvrable while walking. The walking gait of gulls includes a slight side to side motion, something that can be exaggerated in breeding displays. In the air, they are able to hover and they are also able to take off quickly with little space. The general pattern of plumage in adult gulls is a white body with a darker mantle; the extent to which the mantle
11742-496: The spread of the northern fulmar through the United Kingdom is attributed in part to the availability of discards. Discards generally benefit surface feeders, such as gannets and petrels, to the detriment of pursuit divers like penguins and guillemots, which can get entangled in the nets. Fisheries also have negative effects on seabirds, and these effects, particularly on the long-lived and slow-breeding albatrosses, are
11856-695: The squid eaten are too large to have been caught alive, and include mid-water species likely to be beyond the reach of albatrosses. 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. 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. Most species will only have one clutch
11970-462: The surface when hunting. Examples of such associations include four species of gulls feeding around plumes of mud brought to the surface by feeding grey whales , and also between orcas (largest dolphin species) and kelp gulls (and other seabirds). Looking at the effect of humans on gull diet, overfishing of target prey such as sardines have caused a shift in diet and behaviour. Analysis of yellow-legged gull's ( Larus michahellis ) pellets off
12084-495: The theme. Many seabirds feed on the ocean's surface, as the action of marine currents 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 flying (for example as practiced by gadfly petrels , frigatebirds , and storm petrels ), and surface feeding while swimming (examples of which are practiced by gulls , fulmars , many of
12198-491: The three species ( Red and Red-necked ) are oceanic for nine months of the year, crossing the equator to feed pelagically. Loons and grebes , which nest on lakes but winter at sea, are usually categorized as water birds, not seabirds. Although there are a number of sea ducks in the family Anatidae that are truly marine in the winter, by convention they are usually excluded from the seabird grouping. Many waders (or shorebirds) and herons are also highly marine, living on
12312-499: 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 US Navy battleships is the same as that of Antarctic prions , 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
12426-448: The water, and gulls may swim in tight circles or foot paddle to bring marine invertebrates up to the surface. Food is also obtained by searching the ground, often on the shore among sand, mud or rocks. Larger gulls tend to do more feeding in this way. In shallow water gulls may also engage in foot paddling. One method of obtaining prey involves dropping heavy shells of clams and mussels onto hard surfaces. Gulls may fly some distance to find
12540-444: The whale as it surfaces and pecking out pieces of flesh. Gulls range in size from the little gull , at 120 grams ( 4 + 1 ⁄ 4 ounces) and 29 centimetres ( 11 + 1 ⁄ 2 inches), to the great black-backed gull , at 1.75 kg (3 lb 14 oz) and 76 cm (30 in). They are generally uniform in shape, with heavy bodies, long wing, and moderately long necks. The tails of all but three species are rounded;
12654-422: The wings. The skuas range in size from the long-tailed skua , Stercorarius longicauda , at 310 grams (0.68 pounds), to the brown skua , Stercorarius antarcticus , at 1.63 kg (3.6 lb). On average, a skua is about 56 cm (22 in) long, and 121 cm (48 in) across the wings. They have longish bills with a hooked tip, and webbed feet with sharp claws. They look like large dark gulls, but have
12768-407: The winter, but the extent to which they migrate varies by species. Some migrate long distances, notably Sabine's gull , which migrates from the Arctic coasts to winter off the west coasts of South America and southern Africa, and Franklin's gull , which migrates from Canada to wintering grounds off the west coast of South America. Other species move much shorter distances and may simply disperse along
12882-584: Was 22 metres (72 ft); another study, this time on Cory's shearwaters 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. Colonies are usually situated on islands, cliffs or headlands, which land mammals have difficulty accessing. This is thought to provide protection to seabirds, which are often very clumsy on land. Coloniality often arises in types of bird that do not defend feeding territories (such as swifts , which have
12996-679: Was convinced of the need to declare Pelican Island in Florida a National Wildlife Refuge to protect the bird colonies (including the nesting brown pelicans ), and in 1909 he protected the Farallon Islands. Today many important seabird colonies are given some measure of protection, from Heron Island in Australia to Triangle Island in British Columbia. Island restoration techniques, pioneered by New Zealand, enable
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