Pelican Update

[Mood Phaneuf]

Pelicans (genus Pelecanus) are a genus of large water birds that make up the family Pelecanidae. They are characterized 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, except for the brown and Peruvian pelicans. The bills, pouches, and bare facial skin of all pelicans become brightly coloured before the breeding season.

The eight living pelican species have a patchy, seasonally-dependent yet global distribution, ranging latitudinally from the tropics to the temperate zone. Pelicans are absent from interior Amazonian South America, from polar regions and the open ocean; at least one species is known to migrate to the inland desert of Australia's Red Centre, after heavy rains create temporary lakes. White pelicans are also observed at the American state of Utah's Great Salt Lake, for example, some 600 miles (965 km) from the nearest coastline (the Pacific West Coast). They have also been seen hundreds of miles inland in North America, having flown northwards along the Mississippi River and other large waterways.

Long thought to be related to frigatebirds, cormorants, tropicbirds, and gannets and boobies, pelicans instead are most closely related to the shoebill and hamerkop storks (although these two birds are not actually true 'storks'), 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 36 million years to the remains of a tibiotarsus recovered from late Eocene strata of Egypt that bears striking similarity to modern species of pelican.[1] 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.[3] This hypothesis is supported by fossil evidence from the oldest pelican taxa.[1]

The genus Pelecanus was first formally described by Carl Linnaeus in his landmark 1758 10th edition of 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.[9]

The family Pelecanidae was introduced (as Pelicanea) by the French polymath Constantine Samuel Rafinesque in 1815.[10][11] 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.[12] Molecular evidence suggests that the shoebill and the hamerkop form a sister group to the pelicans,[13] though some doubt exists as to the exact relationships among the three lineages.[14]

The oldest known record of Pelicans is a right tibiotarsus very similar to those of modern species from the Birket Qarun Formation in the Wadi El Hitan in Egypt, dating to the late Eocene (Priabonian), referred to the genus Eopelecanus.[1]

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,[4] are sometimes separated from the others by placement in the subgenus Leptopelecanus[15] 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.[3]

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,[15] though to not hinder the swallowing of large fish, the tongue itself is tiny.[50] They have a long neck and short stout legs with large, fully webbed feet. Although they are among the heaviest of flying birds,[51] 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.[15] 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.[52]

Males are generally larger than females and have longer bills.[15] 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,[53] the longest of any bird.[4]

Pelicans have mainly light-coloured plumage, the exceptions being the brown and Peruvian pelicans.[54] The bills, pouches, and bare facial skin of all species become brighter before breeding season commences.[55] 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.[5] The plumage of immature pelicans is darker than that of adults.[54] 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.[56]

Anatomical dissections of two brown pelicans in 1939 showed that pelicans have a network of 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.[57] 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.[57] The air sacs serve to keep the pelican remarkably buoyant in the water[58] 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.[57] 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.[57]

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).[4] 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.[15] Subfossil bones have been recovered from as far south as New Zealand's South Island,[59] although their scarcity and isolated occurrence suggests that these remains may have merely been vagrants from Australia (much as is the case today).[60]

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,[61] combined both with gliding and with flapping flight in V formation, to commute distances up to 150 km (93 mi) to feeding areas.[4] 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.[62] Hence, substantial energy is saved while flying.[63]

Adult pelicans rely on visual displays and behaviour to communicate,[64] 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.[65] Adult pelicans grunt when at the colony, but are generally silent elsewhere or outside breeding season.[32][66][67][68] Conversely, colonies are noisy, as chicks vocalise extensively.[64]

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.[4] 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.[55]

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