Along with the darters, cormorants, gannets, boobies, frigatebirds, and tropicbirds, pelicans make up the order Pelecaniformes. Modern pelicans are found on all continents except Antarctica. They occur mostly in warm regions, though breeding ranges reach 45° south (Australian Pelican, P. conspicillatus) and 60° North (American White Pelicans, P. erythrorhynchos, in western Canada). Birds of inland and coastal waters, they are absent from polar regions, the deep ocean, oceanic islands, and inland South America.
Pelicans are large birds with enormous, pouched bills. The smallest is the Brown Pelican (P. occidentalis), small individuals of which can be as little as 2.75 kg (6 lb), 106 cm (42 in) long and can have a wingspan of as little as 1.83 m (6 ft). The largest is believed to be the Dalmatian Pelican (P. crispus), at up to 15 kg (33 lb), 183 cm (72 in) long, with a maximum wingspan of nearly 3.5 m (11.5 ft). The Australian Pelican has the longest bill of any bird.
Pelicans swim well with their short, strong legs and their feet with all four toes webbed (as in all birds placed in the order Pelecaniformes). The tail is short and square, with 20 to 24 feathers. The wings are long and have the unusually large number of 30 to 35 secondary flight feathers. A layer of special fibers deep in the breast muscles can hold the wings rigidly horizontal for gliding and soaring. Thus they can exploit thermals to commute over 150 km (100 miles) to feeding areas.
Pelicans rub the backs of their heads on their preen glands to pick up its oily secretion, which they transfer to their plumage to waterproof it.
The regular diet of a Pelican usually consists of fish, but they also eat amphibians, crustaceans and on some occasions, smaller birds. They often catch fish by expanding the throat pouch. Then they must drain the pouch above the surface before they can swallow. This operation takes up to a minute, during which time other seabirds are particularly likely to steal the fish. Pelicans in their turn sometimes pirate prey from other seabirds.
The white pelicans often fish in groups. They will form a line to chase schools of small fish into shallow water, and then simply scoop them up. Large fish are caught with the bill-tip, then tossed up in the air to be caught and slid into the gullet head first.
The Brown Pelican of North America usually plunge-dives for its prey. Rarely, other species such as the Peruvian Pelican and the Australian Pelican practice this method.
A Pelican in St. James' Park in London was once filmed eating a fully grown Pigeon alive.
In all species copulation begins shortly after pairing and continues for 3 to 10 days before egg-laying. The male brings the nesting material, ground-nesters (which may not build a nest) sometimes in the pouch and tree-nesters crosswise in the bill. The female heaping the material up to form a simple structure.
Both sexes incubate with the eggs on top of or below the feet. They may display when changing shifts. All species lay at least two eggs, and hatching success for undisturbed pairs can be as high as 95 percent, but because of competition between siblings or outright siblicide, usually all but one nestling dies within the first few weeks (or later in the Pink-backed and Spot-billed species). The young are fed copiously. Before or especially after being fed, they may seem to have a seizure that ends in falling unconscious; the reason is not clearly known.
Parents of ground-nesting species have another strange behavior: they sometimes drag older young around roughly by the head before feeding them. The young of these species gather in "pods" or "crèches" of up to 100 birds in which parents recognize and feed only their own offspring. By 6 to 8 weeks they wander around, occasionally swimming, and may practice communal feeding.
Young of all species fledge 10 to 12 weeks after hatching. They may remain with their parents afterwards, but are now seldom or never fed. Overall breeding success is highly inconsistent.
Pairs are monogamous for a single season, but the pair bond extends only to the nesting area; mates are independent away from the nest.
From the fossil record, it is known that pelicans have been around for over 40 million years, the earliest fossil Pelecanus being found in early Miocene deposits in France. Prehistoric genera have been named Protopelicanus and Miopelecanus. The supposed Miocene pelican Liptornis from Argentina is a nomen dubium, being based on hitherto indeterminable fragments.
A number of fossil species are also known from the extant genus Pelecanus:
In medieval Europe, the pelican was thought to be particularly attentive to her young, to the point of providing her own blood when no other food was available. As a result, the pelican became a symbol of the Passion of Jesus and of the Eucharist. It also became a symbol in bestiaries for self-sacrifice, and was used in heraldry ("a pelican in her piety" or "a pelican vulning (wounding) herself"). Another version of this is that the pelican used to kill its young and then resurrect them with its blood, this being analogous to the sacrifice of Jesus. Thus the symbol of the Irish Blood Transfusion Service (IBTS) is a pelican, and for most of its existence the headquarters of the service was located at Pelican House in Dublin, Ireland.
For example, the emblems of both Corpus Christi College, Cambridge and Corpus Christi College, Oxford are pelicans, showing its use as a medieval Christian symbol ('Corpus Christi' means 'body of Christ').
Likewise a folktale from India says that a pelican killed her young by rough treatment but was then so contrite that she resurrected them with her own blood.
These legends may have arisen because the pelican used to suffer from a disease that left a red mark on its chest. Alternatively it may be that pelicans look as if they are stabbing themselves as they often press their bill into their chest to fully empty their pouch. Yet other possibilities are that they often rest their bills on their breasts, and that the Dalmatian Pelican has a blood-red pouch in the early breeding season.
The symbol is used today on the Louisiana state flag and Louisiana state seal, as the Brown pelican is the Louisiana state bird. Likewise, the pelican is featured prominently on the seal of Louisiana State University. A pelican logo is also used by the Portuguese bank Montepio Geral.