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.
There are more than half a dozen species of pelicans, but all of them have the famous throat pouch for which the birds are best known. These large birds use their elastic pouches to catch fish—though different species use it in different ways.
Hunting and Feeding Edit
Many pelicans fish by swimming in cooperative groups. They may form a line or a "U" shape and drive fish into shallow water by beating their wings on the surface. When fish congregate in the shallows, the pelicans simply scoop them up. The brown pelican, on the other hand, dives on fish (usually a type of herring called menhaden) from above and snares them in its bill. Pelicans do not store fish in their pouch, but simply use it to catch them and then tip it back to drain out water and swallow the fish immediately. The American white pelican can hold some 3 gallons (11 1/2 liters) of water in its bill. Young pelicans feed by sticking their bills into their parents' throats to retrieve food.
Pelicans are found on many of the world's coastlines and also along lakes and rivers. They are social birds and typically travel in flocks, often strung out in a line. They also breed in groups called colonies, which typically gather on islands. In North America, the brown pelican is endangered, but populations are recovering to some extent. The sea birds were devastated by chemical pesticides, such as DDT, which damaged the eggs of pelicans and many other species.
Breeding and Lifespan Edit
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 will 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.
In all species copulation takes place at the nest site; it begins shortly after pairing and continues for 3–10 days before egg-laying. 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 percent 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 parent’s pouch and feed themselves. Sometimes 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 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.