Editing Sheathbill

{{Short description|Genus of birds}}
{{automatic taxobox
| name = Sheathbills 
| image = Snowy Sheathbill.jpg
| image_caption = [[Snowy sheathbill]] (''C.{{nbsp}}albus'')
| display_parents = 2
| parent_authority = [[Charles Lucien Jules Laurent Bonaparte|Bonaparte]], 1832
| taxon = Chionis
| authority = [[Johann Reinhold Forster|J.R. Forster]], 1788<ref>''Enchiridion Historiae Naturali'': [http://biodiversitylibrary.org/page/25760780 37].</ref>
| type_species = ''[[Chionis albus|Vaginalis alba]]''
| type_species_authority = [[Johann Friedrich Gmelin| Gmelin, JF]], 1789
| subdivision_ranks = Species
| subdivision = ''[[Snowy sheathbill|Chionis albus]]'' <br />
''[[Black-faced sheathbill|Chionis minor]]''
}}

The '''sheathbills''' are a [[family (biology)|family]] of [[bird]]s, '''Chionidae'''. Classified in the wader order [[Charadriiformes]], the family consists of one genus, '''''Chionis''''' with two species. They breed on [[subantarctic islands]] and the [[Antarctic Peninsula]], and the [[snowy sheathbill]] [[Bird migration|migrate]]s to the [[Falkland Islands]] and coastal southern [[South America]] in the southern winter; they are the only bird family [[endemism in birds|endemic]] as breeders to the Antarctic region.<ref name=Firefly>{{cite book | last = Mead | first = Christopher J. | author2 = Richford, Andrew S. | year = 2003 | chapter = Sheathbills | editor = Perrins, Christopher | editor-link = Chris Perrins | title = The Firefly Encyclopedia of Birds | publisher = Firefly Books | pages = [https://archive.org/details/fireflyencyclope0000unse/page/256 256&ndash;257] | isbn = 1-55297-777-3 | url-access = registration | url = https://archive.org/details/fireflyencyclope0000unse/page/256 }}</ref> They are also the only Antarctic birds without [[Webbed foot|webbed feet]].

==Description==
Sheathbills have white [[plumage]] including a thick layer of [[down feather|down]], with only the face and leg colours distinguishing the two species. They appear plump and [[dove]]-like, but are believed to be similar to the ancestors of the modern [[gull]]s and [[tern]]s.{{Citation needed|date=March 2025}} There is a rudimentary [[Spur (zoology)|spur]] on the "wrist" or [[Carpometacarpal joint|carpal joint]], as in [[plover]]s. The skin around the eye is bare, as is the skin above the bill, which has [[wikt:carbuncular|carbuncular]] swellings. They derive their [[English language|English]] name from the [[Keratin|horny]] sheath which partially covers the upper mandible of their stout bills.<ref name=Firefly/> They are commonly known in the Antarctic as "Mutts" because of their [[Bird call|call]] which is a soft "Mutt, mutt, mutt".{{Citation needed|date=March 2025}}

==Taxonomy==
The genus ''Chionis'' was introduced in 1788 by the German naturalist [[Johann Reinhold Forster]].<ref>{{ cite book | last=Forster | first=Johann Reinhold | author-link=Johann Reinhold Forster | date=1788 | title=Enchiridion historiae naturali inserviens, quo termini et delineationes ad avium, piscium, insectorum et plantarum adumbrationes intelligendas et concinnandas, secundum methodum systematis Linnaeani continentur | language=Latin | location=Halae | publisher=Prostat apud Hemmerde et Schwetschke | page=37 | url=https://www.biodiversitylibrary.org/page/25760780 }}</ref> The [[type species]] is the [[snowy sheathbill]], ''Chionis albus''.<ref>{{ cite book | editor-last=Peters | editor-first=James Lee | editor-link=James L. Peters | year=1934 | title=Check-List of Birds of the World | volume=2 | publisher=Harvard University Press | place=Cambridge, Massachusetts  | page=308 | url=https://www.biodiversitylibrary.org/page/14483121 }}</ref> The genus name is from the [[Ancient Greek]] {{Transliteration|grc|khiōn}} meaning snow.<ref>{{cite book | last=Jobling | first=James A. | year=2010| title=The Helm Dictionary of Scientific Bird Names | publisher=Christopher Helm | location=London | isbn=978-1-4081-2501-4 | page=101 | url=https://archive.org/stream/Helm_Dictionary_of_Scientific_Bird_Names_by_James_A._Jobling#page/n101/mode/1up }}</ref> 

Genetic studies of the order Charadriiformes show the sheathbills to be a [[sister group]] of the thick-knees of the family [[Burhinidae]]. These two groups together are in turn a sister group to the [[Recurvirostridae]]-[[Haematopodidae]] and [[Charadriidae]].<ref>Christidis and Boles, p. 128</ref> Recent research on the [[Magellanic plover]] (''Pluvianellus socialis'') of southern South America has indicated it too may be classified within the sheathbill family.<ref>Christidis and Boles, p. 132</ref><ref>{{cite journal | last1 = Paton | first1 = Tara A. | last2 = Baker | first2 = Allan J. | year = 2006 | title = Sequences from 14 mitochondrial genes provide a well-supported phylogeny of the Charadriiform birds congruent with the nuclear RAG-1 tree | journal = [[Molecular Phylogenetics and Evolution|Mol. Phylogenet. Evol.]] | volume = 39 | issue = 3| pages = 657–667 | doi = 10.1016/j.ympev.2006.01.011 | pmid = 16531074 }}</ref><ref>{{cite journal | last1 = Paton | first1 = T.A. | last2 = Baker | first2 = A.J. | last3 = Groth | first3 = J.G. | last4 = Barrowclough | first4 = G.F. | year = 2003 | title = RAG-1 sequences resolve phylogenetic relationships within charadriiform birds | journal = [[Molecular Phylogenetics and Evolution|Mol. Phylogenet. Evol.]] | volume = 29 | pages = 268–278 | doi = 10.1016/S1055-7903(03)00098-8 | pmid = 13678682 }}</ref><!--If this is accepted, much of this page will have to be moved to a new ''Chionis'' page.--><!--Or a Chionidae page be created instead-->

The two species are:
{{Species table |genus= Chionis  |authority-name=[[Johann Reinhold Forster|J.R. Forster]]|authority-year= 1788 |species-count=two|no-note=y|narrow-percent=75}}

{{Species table/row
|name=snowy sheathbill|binomial=[[Chionis albus]]
|image=File:Chionis blanc - Pale-faced Sheathbill.jpg|image-size=180px |image-alt=
|authority-name=Gmelin, JF|authority-year= 1789|authority-not-original=yes
|range= [[Antarctica]], the [[Scotia Arc]], the [[South Orkneys]], and [[South Georgia]]
|range-image=File:Chionis albus map.svg
|range-image-size=180px
|size=
|habitat=
|hunting=
|iucn-status= LC
|population=
|direction=
|subspecies=
}}

{{Species table/row
|name=black-faced sheathbill|binomial=[[Chionis minor]]
|image=File:Chionis minor à Crozet.jpg|image-size=180px |image-alt=
|authority-name=Hartlaub|authority-year= 1841|authority-not-original=
|range= South African territory of the [[Prince Edward Islands]], the French territories of the [[Crozet Islands]] and [[Kerguelen Islands]], and the Australian territory of [[Heard Island and McDonald Islands|Heard Island]].
|range-image=
|range-image-size=180px
|size=
|habitat=
|hunting=
|iucn-status= LC
|population=
|direction=
|subspecies=
}}
{{Species table/end}}

==Behaviour==
Sheathbills habitually walk on the ground, somewhat like [[rail (bird)|rails]]. They fly only when alarmed or in migration, looking like [[pigeon]]s.<ref name=Firefly/>

===Food and feeding===
The sheathbills are [[scavenger]]s and opportunistic feeders, consuming invertebrates, [[faeces]], and carrion&mdash;including seal [[afterbirth]] and [[stillborn]] [[seal (animal)|seal]] pups&mdash;between the tidelines. They also take chicks and [[Egg (biology)|egg]]s from [[penguin]]s and [[cormorant]]s.{{Citation Needed|date=April 2022}}

The bird has also been observed to directly pilfer milk from the [[elephant seals]]’ teats.<ref>{{cite journal |last1=Sazima |title=Cleaner birds: an overview for the Neotropics |journal=Museu de Zoologia, Universidade Estadual de Campinas |volume=10 |issue=4 |url=https://www.scielo.br/j/bn/a/cx4vzMJnKQMKjDftsVXb5sp/?format=pdf&lang=en}}</ref><ref>{{cite book |last1=Chester |title=Antarctic birds and seals |date=1993 |url=https://www.abebooks.com/Antarctic-Birds-Seals-Pocket-Guide-Chester/769351226/bd}}</ref><ref>{{cite journal |title=Antarctica's Milk-Stealing, Grudge-Holding Seabirds |journal=Boston NPR |date=2016 |url=http://archives.wbur.org/thewildlife/2016/03/29/antarcticas-milk-stealing-grudge-holding-seabirds/}}</ref>

===Breeding===
During the penguin [[breeding season]], which is also the sheathbill breeding season, pairs of sheathbills in penguin colonies maintain [[Territory (animal)|territories]] covering a number of penguin nests. [[Breeding pair|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 [[kleptoparasitism|steal]] the [[krill]] 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 [[Self-grooming|cleaning themselves]].<ref name=Firefly/>

They lay two or three blotchy white eggs in crevices or rock cavities.<ref name=EoB>{{cite book |editor=Forshaw, Joseph|author= Harrison, Colin J.O.|year=1991|title=Encyclopaedia of Animals: Birds|publisher= Merehurst Press|location=London|pages= 109|isbn= 1-85391-186-0}}</ref> The [[Bird nest|nest]]s are lined messily with [[seaweed]], stones, feathers, [[guano]], bones, and occasionally [[Plastic pollution|plastic trash]]; even dead chicks may not be removed. [[Egg incubation|Incubation]] lasts 28 to 32 days, and the young fledge 50 to 60 days later.<ref name=Firefly/>

==References==
{{Reflist}}

{{Charadriiformes|C.|state=collapsed}}
{{taxonbar|from=Q734677}}

==External links==
*[https://web.archive.org/web/20131004043356/http://ibc.lynxeds.com/family/sheathbills-chionidae Sheathbill videos] on the Internet Bird Collection


[[Category:Chionis|*]]