At nearly a foot and half (half a meter) long the bill of a pelican is the longest of any bird. The bill's main function, and probably what drove its evolution, is as a fish-catcher, but it has a multitude of other uses. From excreting excess salt by oozing out a highly saline solution to advertising sexual readiness by growing a two-inch-high (five-centimeter-high) horn on top of it.
Another well-known quirk to the pelican's beak is the pouch, capable of holding the liquid equivalent of two flushes of a toilet. Even though the pelican's tongue is tiny, a complex set of specialized tongue muscles control the pouch. By contracting these muscles, the pelican tightens the pouch after catching a fish, expelling water and forcing the prey down its throat.
Tongue muscles are also used in gular fluttering, a surprisingly effective evaporative cooling mechanism. The bird rapidly flutters the pouch by contracting and relaxing the muscles, kind of like a dog panting, sometimes at a remarkable flutter-rate of 200 times a minute.
Pelicans perform strange-looking exercises to stretch and maintain their pouch in a brand of pelican yoga. They will gape, holding their mouths wide open. In another pose, they point the bill straight up to the sky, stretching the pouch. Or most evocatively, a bird will turn its pouch completely inside out by forcing it over its breast.
When it comes to fishing, the bird uses the beak and pouch as a personal fishing net, capable of catching fish over three-quarters the length of the bill. The bill is highly sensitive, which in murky water or at night allows the pelican to fish by touch alone, useful when some pelicans have to catch four pounds (two kilograms) of food daily. The beak is smooth along the edges, quite useless when trying to grab a slippery fish (unlike some other fishing birds' beaks that are serrated like a streak knife). All is not lost though, the pelican has a mean hook, called a mandibular nail, at the end of its beak, important in nabbing or killing prey. It is also used to preen and to intimidate predators, competitors, and overzealous ornithologists.
Though the bill is rarely used in fights, the birds are not above jabbing at one another or getting into "fencing matches" during the breeding season. During copulation the male will use its massive beak to grab the female's neck or head to hold her. However, maybe because their bill is too big and potentially dangerous, adults do not help their chicks out of the egg at hatching.
Such a fascinating appendage has spawned many stories, such as how pelicans reportedly use their pouches to collect rainwater, and how gulls sometimes sit on top of a pelican's beak and reach in to swipe prey. But one question is answered: that of how a pelican sleeps with such a large beak and long neck. Does the beak flub on the ground? Nope, the pelican simply turns its head backwards 180 degrees and lays the beak on its back. Goodnight.
—David A. O'Connor