|A great white pelican
flying in Walvis Bay, Namibia
Pelicans are a genus of large water birds that make up the family Pelecanidae. They are characterised by a long beak and a large throat pouch used for catching prey and draining water from the scooped-up contents before swallowing. They have predominantly pale plumage, the exceptions being the brown and Peruvian pelicans. The bills, pouches, and bare facial skin of all species become brightly coloured before the breeding season. The eight living pelican species have a patchy global distribution, ranging latitudinally from the tropics to the temperate zone, though they are absent from interior South America and from polar regions and the open ocean.
Long thought to be related to frigatebirds, cormorants, tropicbirds, and gannets and boobies, pelicans instead are now known to be most closely related to the shoebill and hamerkop, and are placed in the order Pelecaniformes. Ibises, spoonbills, herons, and bitterns have been classified in the same order. Fossil evidence of pelicans dates back at least 30 million years to the remains of a beak very similar to that of modern species recovered from Oligocene strata in France. They are thought to have evolved in the Old World and spread into the Americas; this is reflected in the relationships within the genus as the eight species divide into Old World and New World lineages.
Pelicans frequent inland and coastal waters, where they feed principally on fish, catching them at or near the water surface. They are gregarious birds, travelling in flocks, hunting cooperatively, and breeding colonially. Four white-plumaged species tend to nest on the ground, and four brown or grey-plumaged species nest mainly in trees. The relationship between pelicans and people has often been contentious. The birds have been persecuted because of their perceived competition with commercial and recreational fishing. Their populations have fallen through habitat destruction, disturbance, and environmental pollution, and three species are of conservation concern. They also have a long history of cultural significance in mythology, and in Christian and heraldic iconography.
Taxonomy and systematics
The genus Pelecanus was first formally described by Linnaeus in 1758 in the tenth edition of his Systema Naturae'. He described the distinguishing characteristics as a straight bill hooked at the tip, linear nostrils, a bare face, and fully webbed feet. This early definition included frigatebirds, cormorants, and sulids, as well as pelicans. The name comes from the Ancient Greek word pelekan (πελεκάν), which is itself derived from the word pelekys (πέλεκυς) meaning "axe". In classical times, the word was applied to both the pelican and the woodpecker.
The family Pelecanidae was introduced (as Pelicanea) by the French polymath Constantine Samuel Rafinesque in 1815. Pelicans give their name to the Pelecaniformes, an order which has a varied taxonomic history. Tropicbirds, darters, cormorants, gannets, boobies, and frigatebirds, all traditional members of the order, have since been reclassified: tropicbirds into their own order, Phaethontiformes, and the remainder into the Suliformes. In their place, herons, ibises, spoonbills, the hamerkop, and the shoebill have now been transferred into the Pelecaniformes. Molecular evidence suggests that the shoebill and the hamerkop form a sister group to the pelicans, though some doubt exists as to the exact relationships among the three lineages.
|Evolutionary relationships among the extant species based on Kennedy et al. (2013).|
The eight living pelican species were traditionally divided into two groups, one containing four ground-nesters with mainly white adult plumage (Australian, Dalmatian, great white, and American white pelicans), and one containing four grey- or brown-plumaged species which nest preferentially either in trees (pink-backed, spot-billed and brown pelicans), or on sea rocks (Peruvian pelican). The largely marine brown and Peruvian pelicans, formerly considered conspecific, are sometimes separated from the others by placement in the subgenus Leptopelicanus but in fact species with both sorts of appearance and nesting behavior are found in either.
DNA sequencing of both mitochondrial and nuclear genes yielded quite different relationships; the three New World pelicans formed one lineage, with the American white pelican sister to the two brown pelicans, and the five Old World species the other. The Dalmatian, pink-backed, and spot-billed were all closely related to one another, while the Australian white pelican was their next-closest relative. The great white pelican also belonged to this lineage, but was the first to diverge from the common ancestor of the other four species. This finding suggests that pelicans evolved in the Old World and spread into the Americas, and that preference for tree- or ground-nesting is more related to size than genetics.
|Living species of Pelecanus|
|Common and binomial names||Image||Description||Range and status|
|American white pelican
||Length 1.3–1.8 m (4.3–5.9 ft), wingspan 2.44–2.9 m (8.0–9.5 ft), weight 5–9 kg (10–20 lb). Plumage almost entirely white, except for black primary and secondary remiges only visible in flight.||Monotypic. Inland North America, wintering in Mexico. Status: Least Concern.|
||Length up to 1.4 m (4.6 ft), wingspan 2–2.3 m (6.6–7.5 ft), weight 3.6–4.5 kg (7.9–9.9 lb). Smallest pelican; distinguished by brown plumage; feeds by plunge-diving.||Five subspecies. Coastal distribution ranging from North America and the Caribbean to northern South America and the Galapagos. Status: Least Concern.|
||Length up to 1.52 m (5.0 ft), wingspan 2.48 m (8.1 ft), average weight 7 kg (15 lb). Dark with a white stripe from the crown down the sides of the neck.||Monotypic. Pacific Coast of South America from Ecuador and Peru south through to southern Chile. Status: Near Threatened.|
|Great white pelican
||Length 1.40–1.75 m (4.6–5.7 ft), wingspan 2.45–2.95 m (8.0–9.7 ft), weight 10–11 kg (22–24 lb). Plumage white, with pink facial patch and legs.||Monotypic. Patchy distribution from eastern Mediterranean east to Indochina and Malay Peninsula, and south to South Africa. Status: Least Concern.|
||Length 1.60–1.90 m (5.2–6.2 ft), wingspan 2.5–3.4 m (8.2–11.2 ft), weight 4–8.2 kg (8.8–18.1 lb). Predominantly white with black along primaries and very large, pale pink bill.||Monotypic. Australia and New Guinea; vagrant to New Zealand, Solomons, Bismarck Archipelago, Fiji and Wallacea. Status: Least Concern.|
||Length 1.25–1.32 m (4.1–4.3 ft), wingspan 2.65–2.9 m (8.7–9.5 ft), weight 3.9–7 kg (8.6–15.4 lb). Grey and white plumage, occasionally pinkish on the back, with a yellow upper mandible and grey pouch.||Monotypic. Africa, Seychelles and southwestern Arabia; extinct in Madagascar. Status: Least Concern.|
||Length 1.60–1.80 m (5.2–5.9 ft), wingspan 2.70–3.20 m (8.9–10.5 ft), weight 10–12 kg (22–26 lb). Largest pelican; differs from great white pelican in having curly nape feathers, grey legs and greyish-white plumage.||Monotypic. South-eastern Europe to India and China. Status: Near Threatened.|
||Length 1.27–1.52 m (4.2–5.0 ft), wingspan 2.5 m (8.2 ft), weight c. 5 kg (11 lb). Mainly grey-white all over, with a grey hindneck crest in breeding season, pinkish rump and spotted bill pouch.||Monotypic. Southern Asia from southern Pakistan across India east to Indonesia; extinct in the Philippines and possibly eastern China. Status: Near Threatened.|
Pelicans are very large birds with very long bills characterised by a downcurved hook at the end of the upper mandible, and the attachment of a huge gular pouch to the lower. The slender rami of the lower bill and the flexible tongue muscles form the pouch into a basket for catching fish, and sometimes rainwater, though not to hinder the swallowing of large fish, the tongue itself is tiny. They have a long neck and short stout legs with large, fully webbed feet. Although they are among the heaviest of flying birds, they are relatively light for their apparent bulk because of air pockets in the skeleton and beneath the skin, enabling them to float high in the water. The tail is short and square. The wings are long and broad, suitably shaped for soaring and gliding flight, and have the unusually large number of 30 to 35 secondary flight feathers.
Males are generally larger than females and have longer bills. The smallest species is the brown pelican, small individuals of which can be no more than 2.75 kg (6.1 lb) and 1.06 m (3.5 ft) long, with a wingspan of as little as 1.83 m (6.0 ft). The largest is believed to be the Dalmatian, at up to 15 kg (33 lb) and 1.83 m (6.0 ft) in length, with a maximum wingspan of 3 m (9.8 ft). The Australian pelican's bill may grow up to 0.5 m (1.6 ft) long in large males, the longest of any bird.
Pelicans have mainly light-coloured plumage, the exceptions being the brown and Peruvian pelicans. The bills, pouches, and bare facial skin of all species become brighter before breeding season commences. The throat pouch of the Californian subspecies of the brown pelican turns bright red, and fades to yellow after the eggs are laid, while the throat pouch of the Peruvian pelican turns blue. The American white pelican grows a prominent knob on its bill that is shed once females have laid eggs. The plumage of immature pelicans is darker than that of adults. Newly hatched chicks are naked and pink, darkening to grey or black after 4 to 14 days, then developing a covering of white or grey down.
Anatomical dissections of two brown pelicans in 1939 showed that pelicans have a network of subcutaneous air sacs under their skin situated across the ventral surface including the throat, breast, and undersides of the wings, as well as having air sacs in their bones. The air sacs are connected to the airways of the respiratory system, and the pelican can keep its air sacs inflated by closing its glottis, but how air sacs are inflated is not clear. The air sacs serve to keep the pelican remarkably buoyant in the water and may also cushion the impact of the pelican's body on the water surface when they dive from flight into water to catch fish. Superficial air sacs may also help to round body contours (especially over the abdomen, where surface protuberances may be caused by viscera changing size and position) to enable the overlying feathers to form more effective heat insulation and also to enable feathers to be held in position for good aerodynamics.
Distribution and habitat
Modern pelicans are found on all continents except Antarctica. They primarily inhabit warm regions, although breeding ranges extend to latitudes of 45° South (Australian pelicans in Tasmania) and 60° North (American white pelicans in western Canada). Birds of inland and coastal waters, they are absent from polar regions, the deep ocean, oceanic islands (except the Galapagos), and inland South America, as well as from the eastern coast of South America from the mouth of the Amazon River southwards. Subfossil bones have been recovered from as far south as New Zealand's South Island, although their scarcity and isolated occurrence suggests that these remains may have merely been vagrants from Australia (much as is the case today).
Behaviour and ecology
Pelicans swim well with their strong legs and their webbed feet. They rub the backs of their heads on their preen glands to pick up an oily secretion, which they transfer to their plumage to waterproof it. Holding their wings only loosely against their bodies, pelicans float with relatively little of their bodies below the water surface. They dissipate excess heat by gular flutter – rippling the skin of the throat and pouch with the bill open to promote evaporative cooling. They roost and loaf communally on beaches, sandbanks, and in shallow water.
A fibrous layer deep in the breast muscles can hold the wings rigidly horizontal for gliding and soaring. Thus, they use thermals for soaring to heights of 3000 m (10,000 ft) or more, combined both with gliding and with flapping flight in V formation, to commute distances up to 150 km (93 mi) to feeding areas. Pelicans also fly low (or "skim") over stretches of water, using a phenomenon known as ground effect to reduce drag and increase lift. As the air flows between the wings and the water surface, it is compressed to a higher density and exerts a stronger upward force against the bird above. Hence, substantial energy is saved while flying.
Adult pelicans rely on visual displays and behaviour to communicate, particularly using their wings and bills. Agonistic behaviour consists of thrusting and snapping at opponents with their bills, or lifting and waving their wings in a threatening manner. Adult pelicans grunt when at the colony, but are generally silent elsewhere or outside breeding season. Conversely, colonies are noisy, as chicks vocalise extensively.
Breeding and lifespan
Pelicans are gregarious and nest colonially. Pairs are monogamous for a single season, but the pair bond extends only to the nesting area; mates are independent away from the nest. The ground-nesting (white) species have a complex communal courtship involving a group of males chasing a single female in the air, on land, or in the water while pointing, gaping, and thrusting their bills at each other. They can finish the process in a day. The tree-nesting species have a simpler process in which perched males advertise for females. The location of the breeding colony is constrained by the availability of an ample supply of fish to eat, although pelicans can use thermals to soar and commute for hundreds of kilometres daily to fetch food.
The Australian pelican has two reproductive strategies depending on the local degree of environmental predictability. Colonies of tens or hundreds, rarely thousands, of birds breed regularly on small coastal and subcoastal islands where food is seasonally or permanently available. In arid inland Australia, especially in the endorheic Lake Eyre basin, pelicans breed opportunistically in very large numbers of up to 50,000 pairs, when irregular major floods, which may be many years apart, fill ephemeral salt lakes and provide large amounts of food for several months before drying out again.
The male brings the nesting material, in ground-nesting species (which may not build a nest) sometimes in the pouch, and in tree-nesting species crosswise in the bill. The female then heaps the material up to form a simple structure.
The eggs are oval, white, and coarsely textured. All species normally lay at least two eggs; the usual clutch size is one to three, rarely up to six. Both sexes incubate with the eggs on top of or below the feet; they may display when changing shifts. Incubation takes 30–36 days; hatching success for undisturbed pairs can be as high as 95%, but because of sibling competition or siblicide, in the wild, usually all but one nestling dies within the first few weeks (later in the pink-backed and spot-billed species). Both parents feed their young. Small chicks are fed by regurgitation; after about a week, they are able to put their heads into their parents' pouches and feed themselves. Sometimes before, but especially after being fed the pelican chick may seem to "throw a tantrum" by loudly vocalizing and dragging itself around in a circle by one wing and leg, striking its head on the ground or anything nearby and the tantrums sometimes end in what looks like a seizure that results in the chick falling briefly unconscious; the reason is not clearly known, but a common belief is that it is to draw attention to itself and away from any siblings who are waiting to be fed.
Parents of ground-nesting species sometimes drag older young around roughly by the head before feeding them. From about 25 days old, the young of these species gather in "pods" or "crèches" of up to 100 birds in which parents recognise and feed only their own offspring. By 6–8 weeks they wander around, occasionally swimming, and may practise communal feeding. Young of all species fledge 10–12 weeks after hatching. They may remain with their parents afterwards, but are now seldom or never fed. They are mature at three or four years old. Overall breeding success is highly variable. Pelicans live for 15 to 25 years in the wild, although one reached an age of 54 years in captivity.
The diet of pelicans usually consists of fish, but occasionally amphibians, turtles, crustaceans, insects, birds, and mammals are also eaten. The size of the preferred prey fish varies depending on pelican species and location. For example, in Africa, the pink-backed pelican generally takes fish ranging in size from fry up to 400 g (0.9 lb) and the great white pelican prefers somewhat larger fish, up to 600 g (1.3 lb), but in Europe, the latter species has been recorded taking fish up to 1,850 g (4.1 lb). In deep water, white pelicans often fish alone. Nearer the shore, several encircle schools of small fish or form a line to drive them into the shallows, beating their wings on the water surface and then scooping up the prey. Although all pelican species may feed in groups or alone, the Dalmantian, pink-backed, and spot-billed pelicans are the only ones to prefer solitary feeding. When fishing in groups, all pelican species have been known to work together to catch their prey, and Dalmantian pelicans may even cooperate with great cormorants. They catch multiple small fish by expanding the throat pouch, which must be drained above the water surface before swallowing. This operation takes up to a minute, during which time other seabirds may steal the fish.
Large fish are caught with the bill-tip, then tossed up in the air to be caught and slid into the gullet head-first. A gull will sometimes stand on the pelican's head, peck it to distraction, and grab a fish from the open bill. Pelicans in their turn sometimes snatch prey from other waterbirds.
The brown pelican usually plunge-dives head-first for its prey, from a height as great as 10–20 m (33–66 ft), especially for anchovies and menhaden. The only other pelican to feed using a similar technique is the Peruvian pelican, but its dives are typically from a lower height than the brown pelican. The Australian and American white pelicans may feed by low plunge-dives landing feet-first and then scooping up the prey with the beak, but they—as well as the remaining pelican species—primarily feed while swimming on the water. Aquatic prey is most commonly taken at or near the water surface. Although principally a fish eater, the Australian pelican is also an eclectic and opportunistic scavenger and carnivore that forages in landfill sites, as well as taking carrion and "anything from insects and small crustaceans to ducks and small dogs". Food is not stored in a pelican's throat pouch, contrary to popular folklore.
Great white pelicans have been observed swallowing city pigeons in St. James's Park in London. Spokeswoman for the Royal Parks Louise Wood opined that feeding on other birds is more likely with captive pelicans that live in a semiurban environment and are in constant close contact with humans. However, in southern Africa, eggs and chicks of the Cape cormorant are an important food source for great white pelicans. Several other bird species have been recorded in the diet of this pelican in South Africa, including Cape gannet chicks on Malgas Island as well as crowned cormorants, kelp gulls, greater crested terns, and African penguins on Dassen Island and elsewhere. The Australian pelican, which is particularly willing to take a wide range of prey items, has been recorded feeding on young Australian white ibis, and young and adult grey teals and silver gulls. Brown pelicans have been reported preying on young common murres in California and the eggs and nestlings of cattle egrets and nestling great egrets in Baja California, Mexico. Peruvian pelicans in Chile have been recorded feeding on nestlings of imperial shags, juvenile Peruvian diving petrels, and grey gulls. Cannibalism of chicks of their own species is known from the Australian, brown, and Peruvian pelicans.
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