Pelecanidae – Pelicans

The Pelecanidae or Pelicans, are a genus of large water birds. 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 and herons are more distant relatives, and 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. Their populations have fallen through habitat destruction, disturbance and environmental pollution, and three species are of conservation concern.

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.

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 and 1.06 m long, with a wingspan of as little as 1.83 m. The largest is believed to be the Dalmatian, at up to 15 kg and 1.83 m in length, with a maximum wingspan of 3 m. The Australian pelican’s bill may grow up to 0.5 m long in large males, the longest of any bird.

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 it is not clear how air sacs are inflated.