They belong to the Chionididae family and are referred to as such due to the characteristic sheath that covers the bill. They are migratory birds that live in the Antarctic, are middle sized to small and they are white in color. They could easily be mistaken for doves, except for the tact that the dove is bigger than the sheathbill and has no sheath to cover the bill. The sheathbill rarely flies as it has relatively small wings and even in migration, will fly over short distance at a time. They are not the cleanest of birds with regard to their diet, as they will feed on almost anything that seems edible and soft enough to be pecked on, this include carcasses and chicks. The incubation period of an sheathbill egg is a month after which the chick hatches and moves from the nest in a week.

The Antarctic Peninsula has been the home to Sheathbills for a long time and presents to the small white bird the perfect weather conditions for its sustenance and growth. They are classifies as shore birds, but lack the one characteristic that make them true shore birds, an that is webbed feet and for this reason they rarely wade through water to find food for themselves. They are some of the few shore birds that are scavengers, and opportunistic feeders, the sheath bill will literally feed on anything that moves. Depending on the size of the sheathbill, the meal could be anything from an insect on the ground to feaces. They feed on the garbage that has been left behind. They have been known to steal from fishermen As a testament to the opportunistic nature of these birds, they breed at the same time with pigeons and will prey on the pigeon chicks and even on an unwary adult pigeon that is in the wrong place at the wrong time. Adult pigeons that take care of young chicks have to be very careful, lest they are robbed of the meal before their young ones are able to benefit from it. A sheath bill will knock down the chick from the receiving end before the adult pigeon regurgitates the food to the young one. The food falls down and at that point only the sheathbill; the opportunist can eat the food.

Each island of the south Indian Ocean has its own sub species of the sheathbills. There are two species of the sheathbill, the lesser sheathbill and the snowy sheathbills. Of the two, the showy sheathbills are more in population and are even larger with longer wings and a larger wingspan. The average sheathbill weighs between one and two pounds. During winter, these opportunistic feeders move from Europe to South America. During the heat of summer, the sheathbills continue their nestling near pigeon colonies in order to get themselves something to eat. They can tolerate the heat of the winter very well by shuffling their feathers, much to the dismay of pigeons.