Search

Shorebird Species

Lesser Sheathbill

Chionis minor ("Paddy")

Les Underhill
Animal Demography Unit

  Lesser Sheathbill
Photo Les Underhill
Lesser Sheathbill is the only bird species in the Prince Edward Islands without webbed feet

The Lesser Sheathbill (or "Paddy") occurs mostly in colonies of penguins and seals. From a distance it looks like a cross between a domestic chicken and a white pigeon; but it is definitely a wader. Its nearest relatives are probably the oystercatchers. There are two species of sheathbill. They form a distinct family Chionidae within the order Charadriiformes, which includes the shorebirds/waders as the suborder Charadrii. The sheathbills are the only bird family that is endemic to the Antarctic and subantarctic. Unlike most other members of the Charadrii, the males are larger than the females.

The Lesser Sheathbill breeds on four subantarctic archipelagos of the southern Indian Ocean: Kerguelen Islands, Heard and McDonald Islands, Crozet Archipelago, and the Prince Edward Islands. Each of these has a distinct subspecies, with Chionis minor marionensis being the subspecies that is endemic to Marion Island and Prince Edward Island, the two subantarctic islands which are South African possessions. It is likely that the four subspecies have been isolated from each other for 10 000 years, when the northern limit of the pack ice would have provided links between these islands during the last ice age. The total population of the subspecies resident on these two islands is reckoned to be between 4000 and 5500 birds.

There are no records of Lesser Sheathbills along the mainland coast of South Africa. The sheathbills that do occur as vagrants on this coastline are Snowy Sheathbills Chlionis alba, a species that, unlike the Lesser Sheathbill, is a migrant. Snowy Sheathbills breed on the Antarctic Peninsula in summer, and migrate to east coast of South America in autumn. Some of these migrating birds land on ships, mostly fishing vessels, and become vagrants near the ports of destination. Snowy Sheathbills not only reach South Africa in this way, but there are also records in Europe.

Lesser Sheathbills are mostly scavengers, dodging in between penguins at penguin colonies. They are adept at stealing penguin eggs, and at intercepting the boluses of food adult penguins regurgitate to their chicks. They gather at seal colonies, especially during pupping when placentae and umbilical cords are available. The niggle away at the flesh of any seal or pup that dies. Nothing is too gross to be investigated for consumption. They will even peck at wounds on a seal's body to make it bleed so that they can drink the blood. Breeding adult Lesser Sheathbills seldom wander far throughout the year, and movements farther than 1 km from their nest sites are exceptional. Young birds wander a farther, but never beyond their own archipelago.

They are quarrelsome birds, continually scrapping over food items, and chasing each other. They are very inquisitive, and walk right up to people, stealing food, and even pecking at boots to find out if they are edible.

Sheathbills are tough birds, with dense feathers. Under the feathers is a thick layer of down. They are well adapted to their cold environment.

Lesser Sheathbill
Photo Les Underhill
Lesser Sheathbill on Prince Edward Island, December 2001
 
Lesser Sheathbill
Photo Les Underhill
Lesser Sheathbill in King Penguin colony at Cave Bay on Prince Edward Island