Pelicans In Flight
by Lisa Wooten
Title
Pelicans In Flight
Artist
Lisa Wooten
Medium
Photograph - Photographs
Description
Pelicans are a genus of large water birds that makes 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 as well as from polar regions and the open ocean.
Long thought to be related to frigatebirds, cormorants, tropicbirds, 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 the desolate bitterns have been classified in the same order. Fossil evidence of pelicans dates back to 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. 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,20 though in order not to hinder the swallowing of large fish, the tongue itself is tiny.45 They have a long neck and short stout legs with large, fully webbed feet. Although they are among the heaviest of flying birds,46 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.20 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.47
Males are generally larger than females and have longer bills.20 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,48 the longest of any bird.19
Pelicans have mainly light-coloured plumage, the exceptions being the brown and Peruvian pelicans.49 The bills, pouches and bare facial skin of all species become brighter before breeding season commences.50 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.51 The plumage of immature pelicans is darker than that of adults.49 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.52
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.53 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 it is not clear how air sacs are inflated.53 The air sacs serve to keep the pelican remarkably buoyant in the water54 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.53 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. Wikipedia
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January 21st, 2020
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