Gull

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Gull
Temporal range: Early OligocenePresent
Seagull in flight by Jiyang Chen.jpg
Adult ring-billed gull
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Charadriiformes
Suborder: Lari
Family: Laridae
Genera

11, see text

Flying subadult silver gulls at Kiama beach, Sydney, during Christmas 2013 Flying seagulls at Kiama beach during Christmas, Sydney 2013.jpg
Flying subadult silver gulls at Kiama beach, Sydney, during Christmas 2013

Gulls, or colloquially seagulls, are seabirds of the family Laridae in the suborder Lari. They are most closely related to the terns (family Sternidae) and only distantly related to auks, skimmers and even more distantly to waders. Until 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. [1] An older name for gulls is mews, which is cognate with German Möwe, Danish måge, Swedish mås, Dutch meeuw, Norwegian måke/måse and French mouette, and can still be found in certain regional dialects. [2] [3] [4]

Contents

Gulls are typically medium to large birds, usually grey or white, often with black markings on the head or wings. They typically have harsh wailing or squawking calls; stout, longish bills; and webbed feet. Most gulls are ground-nesting 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 which allow them to consume large prey. Gulls are typically coastal or inland species, rarely venturing far out to sea, except for the kittiwakes. [5] 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 typically long-lived birds, with a maximum age of 49 years recorded for the herring gull. [6]

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. [7] Gulls are resourceful, inquisitive, and intelligent, the larger species in particular, [8] demonstrating complex methods of communication and a highly developed social structure. For example, many gull colonies display mobbing behavior, attacking and harassing predators and other intruders. [9] Certain species have exhibited tool-use behavior, such as the herring gull, using pieces of bread as bait with which to catch goldfish, for example. [10] Many species of gulls have learned to coexist successfully with humans and have thrived in human habitats. [11] Others rely on kleptoparasitism to get their food. Gulls have been observed preying on live whales, landing on the whale as it surfaces to peck out pieces of flesh. [12]

Description and morphology

The Pacific gull is a large white-headed gull with a particularly heavy bill. Larus pacificus Bruny Island.jpg
The Pacific gull is a large white-headed gull with a particularly heavy bill.

Gulls range in size from the little gull, at 120 grams (4+14 ounces) and 29 centimetres (11+12 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 wings, and moderately long necks. The tails of all but three species are rounded; 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 a red spot for the larger white-headed species and red, dark red or black in the smaller species. [13]

The gulls are generalist feeders. Indeed, 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 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. [13]

The general pattern of plumage in adult gulls is a white body with a darker mantle; the extent to which the mantle 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 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. [13]

Distribution and habitat

Swallow-tailed gulls are endemic to the Galapagos Islands. Swallow-tailed-gull.jpg
Swallow-tailed gulls are endemic to the Galapagos Islands.

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 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. [13]

Most gull species are migratory, with birds moving to warmer habitats during the winter, but the extent to which they migrate varies by species. Some migrate long distances, like Franklin's gull, which migrates from Canada to wintering grounds in the south of South America. Other species move much shorter distances and may simply disperse along the coasts near their breeding sites. [13]

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. [14] Looking at two species of gulls dependent on human fisheries, Audouin (Ichthyaetus audouinii) and black-backed gulls (Larus fuscus), their breeding distributions (especially the black-backed gull) was heavily impacted by human fishing discards and fishing ports. [14]

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. [15] Gulls in particular had high associations with salinity levels, being the main environmental predictor for waterbird assemblage. [15]

Behaviour

Diet and feeding

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. [16] 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, plant items such as seeds and fruit, human refuse, chips, [17] and even other birds. No gull species 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. [13]

Hartlaub's gull foot paddling, Cape Town

In addition to taking a wide range of prey, gulls display great versatility in how they obtain prey. Prey can be obtained in 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 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. [18] One method of obtaining prey involves dropping heavy shells of clams and mussels onto hard surfaces. [13] Gulls may fly some distance to find 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. [19] 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. [13]


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 the surface when hunting. [13] Examples of such associations include four species of gulls feeding around plumes of mud brought to the surface by feeding grey whales, [20] and also between orcas (largest dolphin species) and kelp gulls (and other seabirds). [21]

Looking at the effect of humans on gull diet, overfishing of target prey such as sardines have caused a shift in diet and behavior. Analysis of yellow-legged gull's (Larus michahellis) pellets off the northwest coast of Spain revealed a shift from a sardine to crustacean-based diet. [22] This shift was linked to higher fishing efficiency and thus overall fish stock depletion. [22] Lastly, closure of nearby open-air landfills limited food availability for the gulls, furthering creating a stress on their shift in diet. [22] 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 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. [23] Human disturbance has also shown to have an effect on gull breeding, in which hatching failure is directly proportional to the amount of disturbance in a given plot. [24]

Breeding

Black-legged kittiwakes nest colonially, but have tiny, closely packed territories Kittiwakes.jpg
Black-legged kittiwakes nest colonially, but have tiny, closely packed territories

Gulls are monogamous and colonial breeders that display mate fidelity that usually lasts for the life of the pair. Divorce of mated pairs does occur, but it apparently has a social cost that persists for 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 in the same location within that colony. 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 birds. Within colonies, gull pairs are territorial, defending an area of varying size around the nesting site from others of their species. This area can be as large as a 5-m radius around the nest in the herring gull to just a tiny area of cliff ledge in the kittiwakes. [13]

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 the colony. Existing pairs re-establish their pair-bonds, and unpaired birds begin courting. Birds 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 through calls and aerial attacks. [13]

The nest of a great black-backed gull, with three typical eggs Larus marinus eggs.jpg
The nest of a great black-backed gull, with three typical eggs

Nest building is also part of the pair-bonding. Gull nests are usually mats of herbaceous matter with a central nest cup. Nests are usually built on the ground, but a few species build nests on cliffs, including the kittiwakes, which almost always nest in such habitats, and in some cases in trees, and high places like Bonaparte's gulls. Species that nest in marshes must construct a nesting platform to keep the nest dry, particularly in 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. [13] In coastal towns, many gulls nest on rooftops and can be observed by nearby human residents.

Clutch size is typically three eggs, although it is two in some of the smaller species and only one egg for the swallow-tailed gull. Within colonies, birds synchronise their laying, with synchronisation being higher in larger colonies, although after a certain point, this levels off. The eggs of gulls are usually dark tan to brown or dark olive with dark splotches and scrawl markings, and are well camouflaged. Both sexes incubate the eggs, with incubation bouts lasting between one and four hours during the day and one parent incubating through the night. [13] Research on various bird species including the gull suggests that females form pair bonds with other females to obtain alloparental care for their dependent offspring, a behavior seen in other animal species, like the elephants, wolves, and the fathead minnow. [25]

Incubation lasts between 22 and 26 days, and begins after laying the first egg, although it is discontinuous until the second egg is laid. This means the first two chicks are born close together, and the third chick some time later. Young chicks are brooded by their parents for about one or two weeks, and often at least one parent remains with them, until they fledge, to guard them. Both parents feed the chicks, although early on in the rearing period, the male does most of the feeding and the female most of the brooding and guarding. [13]

Black-tailed gulls following a ferry in Matsushima, Japan

Taxonomy

The family Laridae was introduced (as Laridia) by the French polymath Constantine Samuel Rafinesque in 1815. [26] [27] The taxonomy of gulls is confused by their widespread distribution zones of hybridization leading to geneflow. Some have traditionally been considered ring species, but recent evidence suggests that this assumption is questionable. [28] Until recently, 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 . [1] 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, "seagull" is a layperson's term that is not used by most ornithologists and biologists. This name is used informally to refer to a common local species or all gulls in general, and has no fixed taxonomic meaning. [29] 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.

Western gull at Point Lobos State Natural Reserve, CA, USA Sea Gull at Point Lobos State Natural Reserve, CA.jpg
Western gull at Point Lobos State Natural Reserve, CA, USA

The American Ornithologists' Union combines the Sternidae, Stercorariidae, and Rhynchopidae as subfamilies in the family Laridae, but recent research [30] [31] [32] indicates this is incorrect.

List of species

This is a list of the 54 gull species, presented in taxonomic sequence.

ImageGenusSpecies
Glaucous-winged Gull RWD1.jpg Larus Linnaeus, 1758
Relict Gull.jpg Ichthyaetus Kaup, 1829
Laughing-gull.jpg Leucophaeus Bruch, 1853
Chroicocephalus ridibundus (summer).jpg Chroicocephalus Eyton, 1836
Cajka mala (Larus minutus) a (4834254958).jpg HydrocoloeusKaup, 1829 (may include Rhodostethia)
Ross's Gull (Rhodostethia rosea) 1 (cropped).jpg RhodostethiaMacGillivray, 1842
Red-legged Kittiwake RWD3.jpg Rissa Stephens, 1826
GULL, IVORY (11-7-10) pismo beach, slo co, ca -01 (5156197737).jpg PagophilaKaup, 1829
Sabine's Gull.jpg XemaLeach, 1819
Creagrus furcatus -Galapagos Islands-8.jpg CreagrusBonaparte, 1854

Evolution

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, USA, is placed in the prehistoric genus Gaviota ; [33] apart from this and the undescribed Early Oligocene fossil, all prehistoric species were tentatively assigned to the modern genus Larus. Among those of them that have been confirmed as gulls, Milne-Edwards' "Larus" elegans and "L." totanoides from the Late Oligocene/Early Miocene of southeast France have since been separated in Laricola . [34]

Two ring-billed gull chicks sitting amongst rocks. Seagull chicks.jpg
Two ring-billed gull chicks sitting amongst rocks.

Related Research Articles

Seabird Birds that have adapted to life within the marine environment

Seabirds are birds that are adapted to life within 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.

Atlantic puffin Species of seabird (Fratercula arctica)

The Atlantic puffin, also known as the common puffin, is a species of seabird in the auk family. It is the only puffin native to the Atlantic Ocean; two related species, the tufted puffin and the horned puffin, are found in the northeastern Pacific. The Atlantic puffin breeds in Québec, Iceland, Norway, Greenland, Newfoundland and Labrador, Nova Scotia and the Faroe Islands, and as far south as Maine in the west and France in the east. The Atlantic Puffin is most commonly found on the Westman Islands, Iceland. Although it has a large population and a wide range, the species has declined rapidly, at least in parts of its range, resulting in it being rated as vulnerable by the IUCN. On land, it has the typical upright stance of an auk. At sea, it swims on the surface and feeds mainly on small fish, which it catches by diving under water, using its wings for propulsion.

Tern Family of seabirds

Terns are seabirds in the family Laridae that have a worldwide distribution and are normally found near the sea, rivers, or wetlands. Terns are treated as a subgroup of the family Laridae which includes gulls and skimmers and consists of eleven genera. They are slender, lightly built birds with long, forked tails, narrow wings, long bills, and relatively short legs. Most species are pale grey above and white below, with a contrasting black cap to the head, but the marsh terns, the Inca tern, and some noddies have dark plumage for at least part of the year. The sexes are identical in appearance, but young birds are readily distinguishable from adults. Terns have a non-breeding plumage, which usually involves a white forehead and much-reduced black cap.

Black-headed gull Species of bird

The black-headed gull is a small gull that breeds in much of the Palearctic including Europe and also in coastal eastern Canada. Most of the population is migratory and winters further south, but some birds reside in the milder westernmost areas of Europe. Small numbers also occur in northeastern North America, where it was formerly known as the common black-headed gull. As is the case with many gulls, it was previously placed in the genus Larus.

European herring gull Species of bird

The European herring gull is a large gull, up to 66 cm (26 in) long. One of the best-known of all gulls along the shores of Western Europe, it was once abundant. It breeds across Northern Europe, Western Europe, Central Europe, Eastern Europe, Scandinavia, and the Baltic states. Some European herring gulls, especially those resident in colder areas, migrate further south in winter, but many are permanent residents, e.g. in Ireland, Britain, Iceland, or on the North Sea shores. They have a varied diet, including fish, crustaceans, and dead animals, as well as some plants.

Great black-backed gull Species of bird

The great black-backed gull, mistakenly called greater black-backed gull by some, is the largest member of the gull family. Described by the Cornell Lab of Ornithology as "the king of the Atlantic waterfront", it is a very aggressive hunter, pirate, and scavenger. It breeds on the European and North American coasts and islands of the North Atlantic and is fairly sedentary, though some move farther south or inland to large lakes or reservoirs. The adult great black-backed gull has a white head, neck and underparts, dark grey wings and back, pink legs and yellow bill.

Yellow-legged gull Species of bird

The yellow-legged gull is a large gull found in Europe, the Middle East and North Africa, which has only recently achieved wide recognition as a distinct species. It was formerly treated as a subspecies of either the Caspian gull L. cachinnans, or more broadly as a subspecies of the herring gull L. argentatus. The genus name is from Latin Larus which appears to have referred to a gull or other large seabird, and the species name honours the German zoologist Karl Michahelles.

Greater crested tern Seabird in the family Laridae

The greater crested tern, also called crested tern or swift tern, is a tern in the family Laridae that nests in dense colonies on coastlines and islands in the tropical and subtropical Old World. Its five subspecies breed in the area from South Africa around the Indian Ocean to the central Pacific and Australia, all populations dispersing widely from the breeding range after nesting. This large tern is closely related to the royal and lesser crested terns, but can be distinguished by its size and bill colour.

Black-legged kittiwake Species of bird

The black-legged kittiwake is a seabird species in the gull family Laridae.

Silver gull Species of bird

The silver gull is the most common gull of Australia. It has been found throughout the continent, but particularly at or near coastal areas. It is smaller than the Pacific gull, which also lives in Australia.

California gull Species of bird

The California gull is a medium-sized gull, smaller on average than the herring gull but larger on average than the ring-billed gull, though it may overlap in size greatly with both.

Kelp gull Species of bird

The kelp gull, also known as the Dominican gull, is a gull that breeds on coasts and islands through much of the Southern Hemisphere. The nominate L. d. dominicanus is the subspecies found around South America, parts of Australia, and New Zealand. L. d. vetula is a subspecies occurring around Southern Africa.

Western gull Species of bird

The western gull is a large white-headed gull that lives on the west coast of North America. It was previously considered conspecific with the yellow-footed gull of the Gulf of California. The western gull ranges from British Columbia, Canada to Baja California, Mexico.

Yellow-footed gull Species of bird

The yellow-footed gull is a large gull, closely related to the western gull and thought to be a subspecies until the 1960s. It is endemic to the Gulf of California.

Swallow-tailed gull The only nocturnal species of seabird in the world

The swallow-tailed gull is an equatorial seabird in the gull family, Laridae. It is the only species in the genus Creagrus, which derives from the Latin Creagra and the Greek kreourgos which means butcher, also from kreas, meat; according to Jobling it would mean "hook for meat" referring to the hooked bill of this species. It was first described by French naturalist and surgeon Adolphe-Simon Neboux in 1846. Its scientific name is originally derived from the Greek word for gull, "Glaros" and via Latin Larus, "gull" and furca "two-tined fork". It spends most of its life flying and hunting over the open ocean. The main breeding location is in the Galápagos Islands, particularly the rocky shores and cliffs of Hood, Tower and Wolf Islands, with lower numbers on most of the other islands. It is more common on the eastern islands where the water is warmer.

Grey gull Species of bird

The grey gull, also known as garuma gull is a medium-sized gull native to South America. Unusual among gulls, it breeds inland in the extremely dry Atacama Desert in northern Chile, although it is present as a non-breeding bird along much of the Pacific coast of South America.

Hartlaubs gull Seabird in the family Laridae endemic to the Atlantic coast of South Africa and Namibia

Hartlaub's gull, also known as the king gull, is a small gull, which is a non-migratory breeding resident endemic to the Atlantic Ocean coastline of South Africa and Namibia. Although it is predominantly coastal or estuarine, it is not a pelagic species, and is rarely seen at sea far from land. It was formerly sometimes considered to be a subspecies of the silver gull, and, as is the case with many gulls, it has traditionally been placed in the genus Larus but is now placed in the genus Chroicocephalus.

Belchers gull Species of bird

Belcher's gull, also known as the band-tailed gull, is a bird in the family Laridae found along the Pacific coast of South America. It formerly included the very similar Olrog's gull as a subspecies, but that bird occurs on the Atlantic coast of South America and is now accepted as Larus atlanticus. Belcher's gull is a medium-sized gull with a blackish mantle, white head and underparts, a black band on the otherwise white tail, and a yellow bill with a red and black tip. Non-breeding adults have a brownish-black head and a white eye-ring. The name of this bird commemorates the British explorer Sir Edward Belcher who performed survey work on the Pacific coast of South America.

American herring gull Species of bird

The American herring gull or Smithsonian gull is a large gull that breeds in North America, where it is treated by the American Ornithologists' Union as a subspecies of herring gull.

Seabird breeding behavior

The term seabird is used for many families of birds in several orders that spend the majority of their lives at sea. Seabirds make up some, if not all, of the families in the following orders: Procellariiformes, Sphenisciformes, Pelecaniformes, and Charadriiformes. Many seabirds remain at sea for several consecutive years at a time, without ever seeing land. Breeding is the central purpose for seabirds to visit land. The breeding period is usually extremely protracted in many seabirds and may last over a year in some of the larger albatrosses; this is in stark contrast with passerine birds. Seabirds nest in single or mixed-species colonies of varying densities, mainly on offshore islands devoid of terrestrial predators. However, seabirds exhibit many unusual breeding behaviors during all stages of the reproductive cycle that are not extensively reported outside of the primary scientific literature.

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Further reading