The sheathbills are a
family
Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...
of
bird
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...
s, Chionidae. Classified in the wader order
Charadriiformes
Charadriiformes (, from ''Charadrius'', the type genus of family Charadriidae) is a diverse order of small to medium-large birds. It includes about 390 species and has members in all parts of the world. Most charadriiform birds live near water an ...
, the family consists of one genus, ''Chionis'' with two species. They breed on
subantarctic
The sub-Antarctic zone is a region in the Southern Hemisphere, located immediately north of the Antarctic region. This translates roughly to a latitude of between 46° and 60° south of the Equator. The subantarctic region includes many islands ...
islands and the
Antarctic Peninsula
The Antarctic Peninsula, known as O'Higgins Land in Chile and Tierra de San Martín in Argentina, and originally as Graham Land in the United Kingdom and the Palmer Peninsula in the United States, is the northernmost part of mainland Antarctic ...
, and the
snowy sheathbill
The snowy sheathbill (''Chionis albus''), also known as the greater sheathbill, pale-faced sheathbill, and paddy, is one of two species of sheathbill. It is usually found on the ground. It is the only land bird native to the Antarctic continent.
...
migrates to the
Falkland Islands
The Falkland Islands (; es, Islas Malvinas, link=no ) is an archipelago in the South Atlantic Ocean on the Patagonian Shelf. The principal islands are about east of South America's southern Patagonian coast and about from Cape Dubouzet ...
and coastal southern
South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...
in the southern winter; they are the only bird family
endemic
Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...
as breeders to the Antarctic region.
They are also the only Antarctic birds without webbed feet.
Taxonomy
The genus ''Chionis'' was introduced in 1788 by the German naturalist
Johann Reinhold Forster
Johann Reinhold Forster (22 October 1729 – 9 December 1798) was a German Continental Reformed church, Reformed (Calvinist) pastor and natural history, naturalist of partially Scottish descent who made contributions to the early ornithology of ...
. The
type species
In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...
is the
snowy sheathbill
The snowy sheathbill (''Chionis albus''), also known as the greater sheathbill, pale-faced sheathbill, and paddy, is one of two species of sheathbill. It is usually found on the ground. It is the only land bird native to the Antarctic continent.
...
. The genus name is from the
Ancient Greek
Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic peri ...
''khiōn'' meaning snow.
Description
They have white
plumage
Plumage ( "feather") is a layer of feathers that covers a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage differ between species and subspecies and may vary with age classes. Within species, ...
including a thick layer of down, with only the face and leg colours distinguishing the two species. They look plump and
dove
Columbidae () is a bird family consisting of doves and pigeons. It is the only family in the order Columbiformes. These are stout-bodied birds with short necks and short slender bills that in some species feature fleshy ceres. They primarily ...
-like, but are believed to be similar to the ancestors of the modern
gull
Gulls, or colloquially seagulls, are seabirds of the family Laridae in the suborder Lari. They are most closely related to the terns and skimmers and only distantly related to auks, and even more distantly to waders. Until the 21st century, m ...
s and
tern
Terns are seabirds in the family Laridae that have a worldwide distribution and are normally found near the sea, rivers, or wetlands. Terns are treated as a subgroup of the family Laridae which includes gulls and skimmers and consists of e ...
s. There is a rudimentary spur on the "wrist" (carpal) joint, as in
plover
Plovers ( , ) are a widely distributed group of wading birds belonging to the subfamily Charadriinae.
Description
There are about 66 species in the subfamily, most of them called "plover" or "dotterel". The closely related lapwing subfa ...
s. The skin around the eye is bare, as is the skin above the bill, which has carbuncular swellings. They derive their
English
English usually refers to:
* English language
* English people
English may also refer to:
Peoples, culture, and language
* ''English'', an adjective for something of, from, or related to England
** English national ide ...
name from the horny sheath which partially covers the upper mandible of their stout bills.
[ They are commonly known in the Antarctic as "Mutts" because of their call which is a soft "Mutt, mutt, mutt"
]
Behaviour
Sheathbills habitually walk on the ground, somewhat like rails
Rail or rails may refer to:
Rail transport
*Rail transport and related matters
*Rail (rail transport) or railway lines, the running surface of a railway
Arts and media Film
* ''Rails'' (film), a 1929 Italian film by Mario Camerini
* ''Rail'' ( ...
. They fly only when alarmed or in migration, looking like pigeon
Columbidae () is a bird family consisting of doves and pigeons. It is the only family in the order Columbiformes. These are stout-bodied birds with short necks and short slender bills that in some species feature fleshy ceres. They primarily ...
s.[
]
Food and feeding
The sheathbills are scavengers and opportunistic feeders, consuming invertebrates, faeces, and carrion—including seal
Seal may refer to any of the following:
Common uses
* Pinniped, a diverse group of semi-aquatic marine mammals, many of which are commonly called seals, particularly:
** Earless seal, or "true seal"
** Fur seal
* Seal (emblem), a device to impr ...
afterbirths and stillborn seal pups—between the tidelines. They also take many chicks and egg
An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...
s from penguin
Penguins (order (biology), order List of Sphenisciformes by population, Sphenisciformes , family (biology), family Spheniscidae ) are a group of Water bird, aquatic flightless birds. They live almost exclusively in the Southern Hemisphere: on ...
s and cormorant
Phalacrocoracidae is a family of approximately 40 species of aquatic birds commonly known as cormorants and shags. Several different classifications of the family have been proposed, but in 2021 the IOC adopted a consensus taxonomy of seven ge ...
s.
The bird has also been observed to directly pilfer milk from the elephant seals
Elephant seals are very large, oceangoing earless seals in the genus ''Mirounga''. Both species, the northern elephant seal (''M. angustirostris'') and the southern elephant seal (''M. leonina''), were hunted to the brink of extinction for oil ...
’ teats.
Breeding
During the penguin breeding season, which is also the sheathbill breeding season, pairs of sheathbills in penguin colonies maintain territories covering a number of penguin nests. Two mated sheathbills often work together to harass adult penguins, nimbly avoiding their attempts to peck; they gain access to the eggs or chicks or steal the krill
Krill are small crustaceans of the order Euphausiacea, and are found in all the world's oceans. The name "krill" comes from the Norwegian
Norwegian, Norwayan, or Norsk may refer to:
*Something of, from, or related to Norway, a country in n ...
that the adult penguins regurgitate to feed their chicks. Near the few human settlements of the region, they boldly forage for offal. Because of this diet, they spend a good deal of time cleaning themselves.[
They lay 2 or 3 blotchy white eggs in crevices or rock cavities.] The nests are lined messily with seaweed, stones, feathers, guano, bones, and occasionally plastic trash; even dead chicks may not be removed. Incubation lasts 28 to 32 days, and the young fledge 50 to 60 days later.[
]
Taxonomy
Genetic studies of the order Charadriiformes show the sheathbills to be a sister group of the thick-knees of the family Burhinidae
The stone-curlews, also known as dikkops or thick-knees, consist of 10 species within the family Burhinidae, and are found throughout the tropical and temperate parts of the world, with two or more species occurring in some areas of Africa, Asia, ...
. These two groups together are a sister group to Recurvostridae-Haematopodidae and Charadriidae. Recent research on the Magellanic plover
The Magellanic plover (''Pluvianellus socialis'') is a rare wader found only in southernmost South America.
Taxonomy
It was long placed in with the other plovers in the family Charadriidae; however, behavioural evidence suggested they were disti ...
(''Pluvianellus socialis'') of southern South America has indicated it too may be classified within the sheathbill family.
The two species:
File:Black faced sheathbill.jpg, Black-faced sheathbill
References
{{taxonbar, from=Q734677
External links
Sheathbill videos
on the Internet Bird Collection
*