Snowy sheathbill (Chionis albus)

Also known as:	American sheathbill, greater sheathbill, pale-faced sheathbill, snowy paddy, wattled sheathbill
Synonyms:	Chionis alba
French:	Chionis blanc

Kingdom	Animalia
Phylum	Chordata
Class	Aves
Order	Charadriiformes
Family	Chionidae
Genus	Chionis (1)
Size	Head-body length: 34 – 41 cm (2) Wingspan: 75 – 80 cm (2)
Weight	460 – 780 g (2)

Classified as Least Concern (LC) on the IUCN Red List (1).

The sheathbills not only have the distinction of being the only widespread land-based birds in the Antarctic, but they are also the only bird family endemic to the Antarctic and sub-Antarctic regions (3) (4). These peculiar birds look somewhat like a cross between a pigeon and a domestic hen (4). Their most obvious feature is the broad, strong, conical-shaped bill, which has a horny sheath that partly covers the nostrils, and several fleshy protrusions called wattles. The body is sturdily built, with strong legs and feet, and elongated wings that provide aerodynamic efficiency while migrating long distances (3) (4). The adult plumage is a bold white, with a thick under-layer that insulates against the bitterly cold weather, but flecked with grey on fledglings (2) (3) (4). The snowy sheathbill is primarily distinguished from the only other sheathbill species, the black-faced sheathbill (Chionis minor), by its more colourful facial features, with a greenish sheath, a pale yellow patch of naked skin around the eyes, and pinkish wattles (3). In the air, the sheathbills have a pigeon-like flight pattern, with rapid wing-beats and sudden movements, but are more commonly seen on land as, due to the un-webbed feet, they are poorly adapted for a life at sea (3) (4).         

The snowy sheathbill breeds on the rocky coastlines of the Antarctic Peninsula and on several islands in the Scotia Arc island system, including the South Shetland Islands, Elephant Island, the South Orkney Islands, South Georgia, and some of the South Sandwich Islands. At other times of the year, vagrants may travel further north, as far as Tierra del Fuego (Chile and Argentina), Patagonia (Argentina), the Falkland Islands and on rare occasions, north-eastern Brazil and South Africa (3) (5).

Outside the breeding season, this coastal bird forages amongst rotting piles of kelp on sandy and rocky beaches along shorelines, and on tussock grass, meadows and lowland bogs, rarely straying further than one kilometre inland (3). While breeding, it is regularly found amongst penguin colonies, and to a lesser extent, cormorant, albatross and seal colonies (3) (5). On some islands, including the Falkland Islands, it may breed close to human settlements, often near old seal or whaling bases, and whilst migrating, it may rest on icebergs and even passing ships (2) (4).

The snowy sheathbill is an opportunistic scavenger that will eat almost anything that it can find or steal. During the winter time, it will scavenge around scrap heaps, or amongst seaweed for a variety of invertebrates, but during summer when seals are breeding, it will gorge upon seal stillbirths, or probe at seal wounds and pick at the flesh or take some blood (4). It will also eat the placenta of birthing seals and even try to consume the umbilical cord of newborns while it is still attached (3). The snowy sheathbill is a messy eater, even known to consume the faeces of seals, and, consequently, it spends a large proportion of its time preening and cleaning its feathers (4). During its own breeding season, the snowy sheathbill takes up and vigorously defends territories, comprising a number of penguin pairs. It will harass the penguins to try and make them regurgitate their krill catch, or steal their eggs and young chicks. 

The snowy sheathbill arrives at breeding areas in October and November, and lays usually two or three creamy coloured, pear-shaped eggs between December and January at intervals of four days (2) (3). The cup-shaped nest is lined with a combination of bones, guano, dead chicks and even rubbish, and the eggs are incubated for 28 to 32 days (2). Once fledged, the young birds begin to forage along the shoreline for scraps of fish, limpets and kelp before leaving the breeding site between April and June to migrate to more northern latitudes (2) (4). The snowy sheathbill is monogamous, with a high degree of fidelity for its breeding site, meaning that more often than not, it will return to the same site each year to breed (2) (3).

Due to its wide distribution and stable population, the snowy sheathbill is not currently considered threatened with extinction (1) (5). This species may have suffered from poisoning from pollution in the past, particularly at Signy Island, and was formerly hunted for food by Norwegian whalers, but today human interactions with this species are limited (2) (3). This bold and inquisitive bird is not shy of people at all, and will feed on food scraps at research stations, harbours and coastal settlements (3) (4). This has allowed populations to increase in certain areas, and some birds will now over-winter in areas that were not used before, such as at South Georgia (3).

Although the snowy sheathbill is not the direct target of any conservation measures, this species will undoubtedly benefit from a number of conservation measures aiming to restore and protect natural habitats within its range, such as those currently being undertaken on the Falkland Islands and South Georgia (6) (7) (8).

For additional information on the snowy sheathbill, see:

• Neotropical Birds Online:
  http://neotropical.birds.cornell.edu/portal/species/overview?p_p_spp=144116

To find out about conservation projects on the Falkland Islands and South Georgia, see:

• Falklands Conservation:
  http://www.falklandsconservation.com/
• The South Georgia Heritage Trust:
  http://www.sght.org/

For more information on this and other bird species please see:

• BirdLife International:
  http://www.birdlife.org

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk

• Endemic: a species or taxonomic group that is only found in one particular country or geographic area.
• Guano: accumulated droppings found where large colonies of animals such as seals, bats or birds occur; it is rich in plant nutrients.
• Incubate: to keep eggs warm so that development is possible.
• Invertebrates: animals with no backbone, such as insects, crustaceans, worms, molluscs, spiders, cnidarians (jellyfish, corals, sea anemones), echinoderms, and others.
• Monogamous: having only one mate during a breeding season, or throughout the breeding life of a pair.
• Placenta: in animals, a temporary organ present in females during pregnancy. The placenta is the primary site of nutrition and gas exchange between the mother and the embryo.
• Territory: an area occupied and defended by an animal, a pair of animals or a colony.
• Vagrant: found occasionally outside normal range.
• Wattle: a fleshy organ that hangs from the bill, throat or eye of some bird species.

1. IUCN Red List (June, 2010)
   http://www.iucnredlist.org/
2. del Hoyo, J., Elliott, A. and Sargatal, J. (2001) Handbook of the Birds of the World. Volume 3: Hoatzin to Auks. Lynx Edicions, Barcelona.
3. Neotropical Birds Online (June, 2010)
   http://neotropical.birds.cornell.edu/portal/species/overview?p_p_spp=144116
4. Perrins, C. (2009) The Encyclopedia of Birds. Oxford University Press, Oxford.
5. BirdLife International (June, 2010)
   http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=3076&m=0
6. Falklands Conservation (June, 2010)
   http://www.falklandsconservation.com/
7. The South Georgia Heritage Trust (June, 2010)
   http://www.sght.org/
8. BirdLife International IBA Factsheet (June, 2010)
   http://www.birdlife.org/datazone/species/index.html?action=SitHTMDetails.asp&sid=19780&m=0