Editing Feather

{{short description|Body-covering structure of birds}}
{{Other uses}}
{{pp-move-indef}}
{{pp-semi|small=yes}}
{{Use dmy dates|date=August 2021}}
[[File:Types de plumes. - Larousse pour tous, -1907-1910-.jpg|thumb|Feather variations]]

'''Feathers''' are [[epidermis (zoology)|epidermal]] growths that form a distinctive outer covering, or [[plumage]], on both [[Bird|avian]] (bird) and some non-avian [[dinosaur]]s and other [[archosaur]]s. They are the most complex [[integumentary]] structures found in [[vertebrate]]s<ref name=Prum2002>{{Cite journal|author1=[[Richard Prum|Prum, Richard O]]. |author2=AH Brush |year=2002|title=The evolutionary origin and diversification of feathers|journal=[[The Quarterly Review of Biology]]|volume=77|issue=3|url=http://www.yale.edu/eeb/prum/pdf/Prum_n_Brush_2002.pdf|pages=261–295|doi=10.1086/341993|pmid=12365352|s2cid=6344830|access-date=7 July 2010|url-status=live|archive-url=https://web.archive.org/web/20110629175850/http://www.yale.edu/eeb/prum/pdf/Prum_n_Brush_2002.pdf|archive-date=29 June 2011}}</ref><ref name="Prum2003">{{Cite journal |doi=10.1038/scientificamerican0303-84 |date=March 2003 |author1=Prum, R.O. |author2=Brush, A.H |name-list-style=amp |title=Which Came First, the Feather or the Bird? |journal=[[Scientific American]] |volume=288 |issue=3 |pages=84–93 |doi-broken-date=1 November 2024 |url=http://www.yale.edu/eeb/prum/pdf/Prum_n_Brush_2003.pdf |access-date=7 July 2010 |pmid=12616863 |url-status=live |archive-url=https://web.archive.org/web/20110629175910/http://www.yale.edu/eeb/prum/pdf/Prum_n_Brush_2003.pdf |archive-date=29 June 2011 |bibcode=2003SciAm.288c..84P }}</ref> and an example of a complex evolutionary novelty.<ref name=Prum1999>{{Cite journal |doi=10.1002/(SICI)1097-010X(19991215)285:4<291::AID-JEZ1>3.0.CO;2-9 |year=1999 |author=Prum, Richard O |title=Development and Evolutionary Origin of Feathers |journal=Journal of Experimental Zoology Part B: Molecular and Developmental Evolution |volume=285 |issue=4 |pages=291–306 |pmid=10578107 |bibcode=1999JEZ...285..291P |url=http://www.ncsce.org/PDF_files/feathers/Prum%20feather.pdf |access-date=7 July 2010 |archive-url=https://web.archive.org/web/20110409103417/http://ncsce.org/PDF_files/feathers/Prum%20feather.pdf |archive-date=9 April 2011 }}</ref> They are among the characteristics that distinguish the extant [[Aves|birds]] from other living groups.<ref name="iridescence">{{cite journal |last=Li |first=Quanguo |s2cid=206537426 |title=Reconstruction of ''Microraptor'' and the Evolution of Iridescent Plumage |journal=Science |volume=335 |issue=6073 |pages=1215–1219 |date=9 March 2012 |doi=10.1126/science.1213780 |pmid=22403389 |bibcode=2012Sci...335.1215L}}</ref>

Although feathers cover most of the bird's body, they arise only from certain well-defined tracts on the skin. They aid in flight, thermal insulation, and waterproofing. In addition, coloration helps in communication and [[crypsis|protection]].<ref name=pettingill>{{Cite book|author=Pettingill, OS Jr.|year=1970|title=Ornithology in Laboratory and Field. Fourth edition|publisher=Burgess Publishing Company|isbn=0-8087-1609-3|pages=[https://archive.org/details/ornithologyinlab0000pett/page/29 29–58]|url-access=registration|url=https://archive.org/details/ornithologyinlab0000pett/page/29}}</ref> The study of feathers is called '''plumology''' (or '''plumage science''').<ref name=GalaPlum>{{cite web|title=Galapagos plumology|url=http://www.darwinfoundation.org/datazone/galapagos-research/article/galapagos-plumology/|website=darwinfoundation.org|publisher=Charles Darwin Collections Database by the Charles Darwin Foundation|access-date=24 April 2015|archive-url=https://web.archive.org/web/20160317093057/http://www.darwinfoundation.org/datazone/media/pdf/59/NG_59_1998_Harpp%26Geist_Galapagos_plumology.pdf|archive-date=17 March 2016}}</ref><ref name=LangsFWPlumology>{{cite book|last1=Eichhorn|first1=hrsg. von Manfred|title=Langenscheidt Fachwörterbuch Biologie Englisch: englisch – deutsch, deutsch – englisch|date=2005|publisher=Langenscheidt|location=Berlin [u.a.]|isbn=3-86117-228-3|page=537|edition=1. Aufl.|url=https://books.google.com/books?id=KRJfNmHhIpUC&q=Plumology&pg=PA537|access-date=24 April 2015|url-status=live|archive-url=https://web.archive.org/web/20171217235721/https://books.google.com/books?id=KRJfNmHhIpUC&pg=PA537&lpg=PA537&dq=Plumology&source=bl&ots=2pOkPvbmtz&sig=k-Z7u5Kx289CH0jH_iE9y77oWpE&hl=de&sa=X&ei=dP05VducMMjcaK6WgeAB&ved=0CDkQ6AEwAw#v=onepage&q=Plumology&f=false|archive-date=17 December 2017}}</ref>

People use feathers in many ways that are practical, cultural, and religious. Feathers are both soft and excellent at trapping [[heat]]; thus, they are sometimes used in high-class [[bedding]], especially [[pillow]]s, [[blanket]]s, and [[mattress]]es. They are also used as filling for winter [[clothing]] and outdoor bedding, such as quilted [[Coat (clothing)|coats]] and [[sleeping bag]]s. [[Goose]] and [[eider]] [[Down feather|down]] have great ''loft'', the ability to expand from a compressed, stored state to trap large amounts of compartmentalized, insulating air.<ref>{{Cite journal|journal=Journal of Materials Science Letters|title=The structural mechanical properties of down feathers and biomimicking natural insulation materials|volume=18|issue=21|pages=1769–1770|year=1999|author1=Bonser, R.H.C.  |author2=Dawson, C.|doi=10.1023/A:1006631328233|s2cid=135061282}}</ref> Feathers of large birds (most often [[Goose|geese]]) have been and are used to make [[quill]] pens. Historically, the [[plume hunting|hunting of birds for decorative and ornamental feathers]] has endangered some species and helped to contribute to the extinction of others.<ref name="Missouri">{{cite web |url=http://tam.missouri.edu/MHCTC/exhibit_origins_feather.html |title=Feathers: Endangered – Fauna and Fashion |date=20 September 2018 |first1=Nicole |last1=Johnston |first2=Jean |last2=Parsons |name-list-style=amp |publisher=[[University of Missouri]]'s Historic Costume and Textiles Collection}}</ref> Today, feathers used in fashion and in military headdresses and clothes are obtained as a waste product of poultry farming, including [[chicken]]s, [[goose|geese]], [[Turkey (bird)|turkeys]], [[pheasant]]s, and [[ostrich]]es. These feathers are dyed and manipulated to enhance their appearance, as poultry feathers are naturally often dull in appearance compared to the feathers of wild birds.

==Etymology==
[[File:Parts of feather modified.jpg|thumb|'''Parts of a feather:''' {{ordered list |Vane |Shaft, rachis |Barbs |Aftershaft, afterfeather |Quill, calamus}}]]
Feather derives from the [[Old English]] "feþer", which is of [[Germanic languages|Germanic]] origin; related to Dutch "veer" and German "Feder", from an Indo-European root shared by Sanskrit's "patra" meaning 'wing', Latin's "penna" meaning 'feather', and Greek's "pteron", "pterux" meaning 'wing'.

[[quill|Quills]], which were early pens used for writing, were made from feathers. The word '''pen''' itself is derived from the [[Latin]] ''penna'', meaning feather.<ref>{{cite web|url=http://www.merriam-webster.com/dictionary/pen%5B3%5D|title=pen(3)|work=The Merriam-Webster Online Dictionary|publisher=Merriam-Webster, Inc|access-date=16 October 2010|url-status=live|archive-url=https://web.archive.org/web/20110919225647/http://www.merriam-webster.com/dictionary/pen%5B3%5D|archive-date=19 September 2011}}</ref> The French word ''plume'' can mean ''feather'', ''quill'', or ''pen''.

==Structures and characteristics==
[[File:Feather_zipping_microstructure.svg|thumb|left|Feather microstructure showing interlocking barbules]]
[[File:pigeon_down_SEM.tif|thumb|Anterior region of a contour feather from a [[rock dove]], visualized using [[scanning electron microscopy]]. Interlocking barbules are clearly seen in the middle image.]]
Feathers are among the most complex [[Integumentary system|integumentary]] [[appendages]] found in [[Vertebrata|vertebrates]] and are formed in tiny follicles in the [[Epidermis (zoology)|epidermis]], or outer skin layer, that produce [[keratin]] [[protein]]s. The [[β-keratin]]s in feathers, [[beak]]s and [[claw]]s – and the claws, [[scale (zoology)|scales]] and [[Exoskeleton|shells]] of [[reptile]]s – are composed of protein strands [[hydrogen bond|hydrogen-bonded]] into [[beta sheet|β-pleated sheets]], which are then further twisted and [[cross-link|crosslinked]] by [[disulfide]] bridges into structures even tougher than the [[α-keratin]]s of mammalian [[hair]], [[horn (anatomy)|horns]] and [[hooves]].<ref>{{Cite journal|journal=Biophys. J.| year= 1961| volume= 1| issue= 6| pages= 489–515|title=Studies on the Structure of Feather Keratin: II. A β-Helix Model for the Structure of Feather Keratin|first1= R. |last1= Schor |first2= S. |last2= Krimm |doi=10.1016/S0006-3495(61)86904-X |pmid=19431311 |pmc=1366335 |bibcode=1961BpJ.....1..489S}}</ref><ref>{{Cite journal|title=The Structure of Feather Rachis Keratin| first1= Linus |last1= Pauling |first2= Robert B. |last2= Corey| journal= Proceedings of the National Academy of Sciences of the United States of America| volume= 37| issue= 5| year= 1951| pages= 256–261| doi=10.1073/pnas.37.5.256| pmid= 14834148| pmc= 1063351| bibcode = 1951PNAS...37..256P | doi-access= free }}</ref> The exact [[signal]]s that induce the growth of feathers on the skin are not known, but it has been found that the transcription factor cDermo-1 induces the growth of feathers on skin and scales on the leg.<ref>{{Cite journal|last1=Hornik| first1= C.|last2= Krishan|first2=K.|last3= Yusuf|first3=F.|last4= Scaal| first4= M.|last5= Brand-Saberi| first5= B.| year= 2005| title=cDermo-1 misexpression induces dense dermis, feathers, and scales|journal=Developmental Biology| volume= 277| issue= 1|pages=42–50| doi=10.1016/j.ydbio.2004.08.050| pmid= 15572138|doi-access= free}}</ref>

===Classification===
{{See also|Pennaceous feather|Down feather}}
[[File:Grand Cormoran (Phalacrocorax carbo), Parc de Woluwé, Bruxelles (50915141282).jpg|left|thumb|Filoplumes can be important in nuptial display; in the [[great cormorant]] they are white, and produced on the head and upper neck at the start of the breeding season, and shed soon after nesting.]]
[[File:Parrot-feather.jpg|thumb|Feather structure of a [[blue-and-yellow macaw]]]]
There are two basic types of feather: vaned feathers which cover the exterior of the body, and [[down feather]]s which are underneath the vaned feathers. The [[pennaceous feather]]s are vaned feathers. Also called contour feathers, pennaceous feathers arise from tracts and cover the entire body. A third rarer type of feather, the '''filoplume''', is hairlike and are closely associated with pennaceous feathers and are often entirely hidden by them, with one or two filoplumes attached and sprouting from near the same point of the skin as each pennaceous feather, at least on a bird's head, neck and trunk.<ref name="Nitzsch1867">{{cite book |last=Nitzsch |first=Christian Ludwig |title=Nitzsch's Pterylography |url=https://archive.org/details/nitzschspterylog00nitzrich |year=1867 |publisher=Ray Society |page=[https://archive.org/details/nitzschspterylog00nitzrich/page/14 14] }}</ref><ref name="Chandler261">{{Harvnb|Chandler|1916|p=261}}</ref> Filoplumes are entirely absent in [[ratite]]s.<ref>{{cite journal | last=Chandler | first=Asa C. | year=1916 | title=A study of the structure of feathers, with reference to their taxonomic significance | journal=University of California Publications in Zoology| volume=13| issue=11| pages=243–446 [284] |url=https://www.biodiversitylibrary.org/page/34806138 }}</ref> In some passerines, filoplumes arise exposed beyond the pennaceous feathers on the neck.<ref name=Prum2002/> The remiges, or [[flight feather]]s of the wing, and rectrices, or flight feathers of the tail, are the most important feathers for flight. A typical vaned feather features a main shaft, called the [[rachis]]. Fused to the rachis are a series of branches, or '''barbs'''; the barbs themselves are also branched and form the '''barbules'''. These barbules have minute hooks called '''barbicels''' for cross-attachment. Down feathers are fluffy because they lack barbicels, so the barbules float free of each other, allowing the down to trap air and provide excellent thermal insulation. At the base of the feather, the rachis expands to form the hollow tubular ''calamus'' (or [[quill]]) which inserts into a [[Hair follicle|follicle]] in the [[skin]]. The basal part of the calamus is without vanes. This part is embedded within the skin follicle and has an opening at the base (proximal umbilicus) and a small opening on the side (distal umbilicus).<ref name=atlas>{{Cite book|title=A color atlas of avian anatomy|last= McLelland| first=J.|publisher=W.B. Saunders Co.|year=1991|isbn=0-7216-3536-9}}</ref>

Hatchling birds of some species have a special kind of natal down feathers (neossoptiles) which are pushed out when the normal feathers (teleoptiles) emerge.<ref name=Prum2002 />

Flight feathers are stiffened so as to work against the air in the downstroke but yield in other directions. It has been observed that the orientation pattern of β-keratin fibers in the feathers of flying birds differs from that in flightless birds: the fibers are better aligned along the shaft axis direction towards the tip,<ref>{{Cite journal|last1= Cameron| first1= G.|last2=Wess|first2= T. |last3= Bonser |first3=R.|year=2003|title=Young's modulus varies with differential orientation of keratin in feathers |journal=Journal of Structural Biology| volume= 143| issue= 2|pages=118–23|doi=10.1016/S1047-8477(03)00142-4|pmid=12972348}}</ref><ref>{{Cite journal| last1= Bonser| first1= R.| last2= Saker|first2= L.| last3= Jeronimidis |first3= G. |year=2004 |title=Toughness anisotropy in feather keratin |journal=Journal of Materials Science|volume=39|issue=8|pages=2895–2896| doi=10.1023/B:JMSC.0000021474.75864.ff| bibcode = 2004JMatS..39.2895B | s2cid= 135873731}}</ref> and the lateral walls of rachis region show structure of crossed fibers.<ref name="Wang 2016 1600360">{{Cite journal |last=Wang |first=Bin |title=Light like a feather: A fibrous natural composite with a shape changing from round to square |journal=Advanced Science |volume=4 |issue=3 |year=2016 |doi=10.1002/advs.201600360 |pmid=28331789 |page=1600360|pmc=5357985 }}</ref><ref>{{Cite journal |last=Lingham-Soliar |first=Theagarten |title=A new helical crossed-fibre structure of b-keratin in flight feathers and its biomechanical implications |journal=PLOS ONE|year=2013 |doi=10.1371/journal.pone.0065849 |pmid=23762440 |volume=8 |issue=6 |page=e65849|bibcode=2013PLoSO...865849L |pmc=3677936 |doi-access=free }}</ref>

===Functions===
Feathers insulate birds from water and cold temperatures. They may also be plucked to line the nest and provide insulation to the eggs and young. The individual feathers in the wings and tail play important roles in controlling flight.<ref name="Wang 2016 1600360"/> Some species have a [[Crest (feathers)|crest]] of feathers on their heads. Although feathers are light, a bird's plumage weighs two or three times more than its skeleton, since many bones are hollow and contain air sacs. Color patterns serve as [[camouflage]] against [[predator]]s for birds in their habitats, and serve as camouflage for predators looking for a meal. As with fish, the top and bottom colors may be different, in order to provide camouflage during flight. Striking differences in feather patterns and colors are part of the [[sexual dimorphism]] of many bird species and are particularly important in the selection of mating pairs. In some cases, there are differences in the UV reflectivity of feathers across sexes even though no differences in color are noted in the visible range.<ref>{{Cite journal|title=The ubiquity of avian ultraviolet plumage reflectance|first1= Muir D. |last1= Eaton |first2= Scott M. |last2= Lanyon|journal=Proceedings: Biological Sciences| volume= 270| issue= 1525| year= 2003| pages=1721–1726|doi=10.1098/rspb.2003.2431|pmid=12965000|pmc=1691429}}</ref> The wing feathers of male [[club-winged manakin]]s ''Machaeropterus deliciosus'' have special structures that are used to produce sounds by [[stridulation]].<ref>{{Cite journal| title= Courting Bird Sings with Stridulating Wing Feathers| last1= Bostwick| first1= Kimberly S.| last2= Richard O.| first2= Prum| year= 2005| journal= Science| volume= 309| issue= 5735| page= 736| doi= 10.1126/science.1111701| pmid= 16051789| s2cid= 22278735| url= http://cumv.bio.cornell.edu/pdf/Bostwick_Prum_2005_manuscript.pdf| access-date= 19 July 2010| url-status= live| archive-url= https://web.archive.org/web/20100707152805/http://cumv.bio.cornell.edu/pdf/Bostwick_Prum_2005_manuscript.pdf| archive-date= 7 July 2010}}</ref>
[[File:GuineaFeather.jpg|thumb|left|A contour feather from a [[Guinea fowl]]]]
Some birds have a supply of [[powder down]] feathers that grow continuously, with small particles regularly breaking off from the ends of the barbules. These particles produce a [[Powder (substance)|powder]] that sifts through the feathers on the bird's body and acts as a waterproofing agent and a feather [[conditioner (chemistry)|conditioner]]. Powder down has evolved independently in several taxa and can be found in down as well as in pennaceous feathers. They may be scattered in plumage as in the pigeons and parrots or in localized patches on the breast, belly, or flanks, as in herons and frogmouths. Herons use their bill to break the powder down feathers and to spread them, while cockatoos may use their head as a powder puff to apply the powder.<ref name=delhey/> Waterproofing can be lost by exposure to [[emulsion|emulsifying agents]] due to human pollution. Feathers can then become waterlogged, causing the bird to sink. It is also very difficult to clean and rescue birds whose feathers have been fouled by [[oil spill]]s. The feathers of cormorants soak up water and help to reduce buoyancy, thereby allowing the birds to swim submerged.<ref>{{Cite journal| last1= Ribak| first1= G.| last2= Weihs| first2= D. | last3= Arad| first3= Z.|year=2005|title=Water retention in the plumage of diving great cormorants ''Phalacrocorax carbo sinensis''|journal=J. Avian Biol.|volume=36|pages=89–95|doi=10.1111/j.0908-8857.2005.03499.x|issue=2}}</ref>
[[File:BarbetRictalBristle.jpg|thumb|Rictal bristles of a [[white-cheeked barbet]]]]
[[Bristle]]s are stiff, tapering feathers with a large rachis but few barbs. '''Rictal bristles''' are found around the eyes and bill. They may serve a similar purpose to [[eyelash]]es and [[vibrissae]] in [[mammal]]s. Although there is as yet no clear evidence, it has been suggested that rictal bristles have sensory functions and may help insectivorous birds to capture prey.<ref>{{Cite journal |url=http://sora.unm.edu/sites/default/files/journals/wilson/v084n02/p0193-p0197.pdf |title=The role of avian rictal bristles |last=Lederer |first=Roger J. |year=1972 |journal=[[The Wilson Bulletin]] |volume=84 |pages=193–97 |url-status=live |archive-url=https://web.archive.org/web/20140204025111/http://sora.unm.edu/sites/default/files/journals/wilson/v084n02/p0193-p0197.pdf |archive-date=4 February 2014 }}</ref> In one study, willow flycatchers (''[[Empidonax traillii]]'') were found to catch insects equally well before and after removal of the rictal bristles.<ref>{{Cite journal|url=http://sora.unm.edu/node/103116|last1=Conover|first1=M. R.|last2=Miller|first2=D. E.|year=1980|title=Rictal bristle function in willow flycatcher|journal=Condor|volume=82|pages=469–471|issue=4|doi=10.2307/1367580|url-status=live|archive-url=https://web.archive.org/web/20140222004514/https://sora.unm.edu/node/103116|archive-date=22 February 2014|jstor=1367580|url-access=subscription}}</ref>

[[Grebe]]s are peculiar in their habit of ingesting their own feathers and feeding them to their young. Observations on their diet of fish and the frequency of feather eating suggest that ingesting feathers, particularly down from their flanks, aids in forming easily ejectable pellets.<ref>{{Cite journal|title=Feather eating in Great Crested Grebes ''Podiceps cristatus'': a unique solution to the problems of debris and gastric parasites in fish-eating birds|last1= Piersma| first1= T |first2= M. R. |last2=van Eerden|journal=Ibis|volume=131|issue=4|pages=477–486| year= 1989| doi=10.1111/j.1474-919X.1989.tb04784.x|url= https://pure.rug.nl/ws/files/979340584/Ibis_-_October_1989_-_PIERSMA_-_Feather_eating_in_Great_Crested_Grebes_Podiceps_cristatus_a_unique_solution_to_the.pdf}}</ref>

===Distribution===
[[File:Pterylae.svg|thumb|Feather tracts or pterylae and their naming]]
Contour feathers are not uniformly distributed on the skin of the bird except in some groups such as the [[penguin]]s, ratites and screamers.<ref>{{Cite journal|title=A Study of the Pterylosis and Pneumaticity of the Screamer|jstor=1364475|last=Demay|first=Ida S.|journal=The Condor|url=http://sora.unm.edu/node/99003|volume=42|issue=2|year=1940|pages=112–118|doi=10.2307/1364475|url-status=live|archive-url=https://web.archive.org/web/20140221153848/https://sora.unm.edu/node/99003|archive-date=21 February 2014|url-access=subscription}}</ref> In most birds the feathers grow from specific tracts of skin called ''pterylae''; between the pterylae there are regions which are free of feathers called ''apterylae'' (or ''apteria''). Filoplumes and down may arise from the apterylae. The arrangement of these feather tracts, pterylosis or pterylography, varies across bird families and has been used in the past as a means for determining the evolutionary relationships of bird families.<ref>{{Cite journal|journal=Journal of Ornithology| title= Do nine-primaried passerines have nine or ten primary feathers? The evolution of a concept| volume= 146| issue= 2| pages=121–126| year=2005|author=Hall, K. |author2= Susanna S. |doi=10.1007/s10336-004-0070-5| bibcode= 2005JOrni.146..121H| s2cid= 36055848}}</ref><ref>{{Cite journal|last= Pycraft| first=W. P.|year=1895|title=On the pterylography of the hoatzin (''Opisthocomus cristatus'')| journal= Ibis| volume= 37| pages= 345–373|doi=10.1111/j.1474-919X.1895.tb06744.x|issue=3| url=https://www.biodiversitylibrary.org/part/382407}}</ref> Species that incubate their own eggs often lose their feathers on a region of their belly, forming a [[brooding patch]].<ref>{{Cite journal|last=Turner|first=J. Scott|year=1997|title=On the Thermal Capacity of a Bird's Egg Warmed by a Brood Patch|url=https://www.esf.edu/efb/turner/publication%20pdfs/thermal%20capacity%20of%20eggs.pdf|journal=Physiological Zoology|volume=70|issue=4|pages=470–80|doi=10.1086/515854|pmid=9237308|s2cid=26584982|via=EBSCO|access-date=29 July 2020|archive-date=20 October 2022|archive-url=https://web.archive.org/web/20221020202108/https://www.esf.edu/efb/turner/publication%20pdfs/thermal%20capacity%20of%20eggs.pdf|url-status=dead}}</ref>

===Coloration===
[[File:Red feather pigments.jpg|thumb|left|Colors resulting from different feather pigments<br />'''Left:''' [[turacin]] (red) and [[turacoverdin]] (green, with some structural blue [[iridescence]] at lower end) on the wing of ''[[Tauraco bannermani]]''<br />'''Right:''' [[carotenoid]]s (red) and [[melanin]]s (dark) on belly/wings of ''[[Ramphocelus bresilius]]'']]
The colors of feathers are produced by pigments, by microscopic structures that can [[refraction|refract]], reflect, or scatter selected wavelengths of light, or by a combination of both.

Most feather pigments are [[melanin]]s (brown and beige [[pheomelanin]]s, black and grey [[eumelanin]]s) and [[carotenoid]]s (red, yellow, orange); other pigments occur only in certain [[taxa]] – the yellow to red [[psittacofulvin]]s<ref>{{Cite journal|journal=Biology Letters|title=Distribution of unique red feather pigments in parrots|volume=1|issue=1|pages=38–43|year=2005|last1= McGraw |first1=KH |first2= MC |last2= Nogare| doi=10.1098/rsbl.2004.0269| pmid= 17148123|pmc=1629064}}</ref> (found in some [[parrot]]s) and the red [[turacin]] and green [[turacoverdin]] ([[porphyrin]] pigments found only in [[turaco]]s).

[[Structural coloration]]<ref name=pettingill/><ref>{{Cite journal| last1= Hausmann| first1= F.| last2= Arnold| first2=K.E.| last3= Marshall| first3= N.J. | last4= Owens| first4= I.P.F.|year=2003|title=Ultraviolet signals in birds are special|journal=Proceedings of the Royal Society B|volume= 270|pages= 61–67| doi=10.1098/rspb.2002.2200| pmid= 12590772| issue= 1510|pmc=1691211}}</ref><ref>{{Cite journal|title= Carotenoids need structural colours to shine|first1= Matthew D|last1= Shawkey|first2= Geoffrey E|last2= Hill|journal= Biol. Lett.|year= 2005|volume= 1|issue= 2|pages= 121–124|doi= 10.1098/rsbl.2004.0289|url= http://nature.berkeley.edu/%7Emshawkey/9.pdf|pmid= 17148144|pmc= 1626226|archive-url= https://web.archive.org/web/20090326144121/http://nature.berkeley.edu/%7Emshawkey/9.pdf|archive-date= 26 March 2009}}</ref> is involved in the production of blue colors, [[iridescence]], most [[ultraviolet]] reflectance and in the enhancement of pigmentary colors. Structural iridescence has been reported<ref>{{Cite journal |last1= Vinther |first1= Jakob |first2= Derek E. G. |last2= Briggs |first3= Julia |last3= Clarke |first4= Gerald |last4= Mayr |first5= Richard O. |last5= Prum |year= 2009 |pages= 128–31 |issue= 1 |volume= 6 |title= Structural coloration in a fossil feather |journal= [[Biology Letters]] |doi= 10.1098/rsbl.2009.0524 |pmc= 2817243 |pmid= 19710052 |url= http://www.eeb.yale.edu/prum/pdf/Vinther%20et%20al%202010.pdf |access-date= 19 July 2010 |archive-url= https://web.archive.org/web/20100621083621/http://www.eeb.yale.edu/prum/pdf/Vinther%20et%20al%202010.pdf |archive-date= 21 June 2010 }}</ref> in fossil feathers dating back 40 million years. White feathers lack pigment and scatter light diffusely; [[albinism in birds]] is caused by defective pigment production, though structural coloration will not be affected (as can be seen, for example, in blue-and-white [[budgerigar]]s).

[[File:BWfeather.jpg|thumb|upright|A feather with no pigment]]
The blues and bright greens of many [[parrot]]s are produced by constructive interference of light reflecting from different layers of structures in feathers. In the case of green plumage, in addition to yellow,<!-- was: carotinoid, but according to the psittacofulvin source Psittaciformes this might not be correct --> the specific feather structure involved is called by some the Dyck texture.<ref>{{Cite journal|last= Dyck |first=J.|title= Structure and spectral reflectance of green and blue feathers of the Lovebird (''Agapornis roseicollis'')| journal= Biol. SKR.| year= 1971|volume=18|pages=1–67}}</ref><ref>{{Cite journal|journal=The Auk|volume=121|issue=3|pages=652–655|year=2005|title=Feathers at a fine scale|last1=Shawkey|first1=M. D.|first2=G. E.|last2=Hill|doi=10.1642/0004-8038(2004)121[0652:FAAFS]2.0.CO;2|doi-access=free}}</ref> Melanin is often involved in the absorption of light; in combination with a yellow pigment, it produces a dull olive-green.

[[File:Pedro Américo - D. Pedro II na abertura da Assembléia Geral (cropped).jpg|thumb|Emperor [[Pedro II of Brazil]] wearing a wide collar of orange toucan feathers around his shoulders and elements of the [[Imperial Regalia of Brazil|Imperial Regalia]]. Detail from a painting by [[Pedro Américo]]]]
In some birds, feather colors may be created, or altered, by secretions from the [[uropygial gland]], also called the preen gland. The yellow bill colors of many hornbills are produced by such secretions. It has been suggested that there are other color differences that may be visible only in the ultraviolet region,<ref name=delhey>{{Cite journal|last1=Delhey|first1=K|first2=A.|last2=Peters|first3=B.|last3=Kempenaers|year=2007|title=Cosmetic coloration in birds: occurrence, function and evolution|journal=Am. Nat.|volume=169|issue=S1|pages=S145–158|url=http://www.orn.mpg.de/documents/peters/Delhey_AmNat2007_copy.pdf|doi=10.1086/510095|pmid=19426089|bibcode=2007ANat..169S.145D|s2cid=29592388|archive-url=https://web.archive.org/web/20071203190459/http://www.orn.mpg.de/documents/peters/Delhey_AmNat2007_copy.pdf|archive-date=3 December 2007}}</ref> but studies have failed to find evidence.<ref>{{Cite journal|last1= Delhey| first1= K.| first2= A. |last2= Peters| first3= P. H. W.| last3= Biedermann |first4= B. |last4= Kempenaers|year=2008|title=Optical properties of the uropygial gland secretion: no evidence for UV cosmetics in birds|journal=Naturwissenschaften|doi=10.1007/s00114-008-0406-8|volume=95|pages=939–46| pmid= 18560743| issue= 10| bibcode = 2008NW.....95..939D |doi-access= free|hdl= 11858/00-001M-0000-0010-509C-A|hdl-access= free}}</ref> The oil secretion from the uropygial gland may also have an inhibitory effect on feather bacteria.<ref>{{Cite journal|last1=Shawkey|first1=M. D.|first2=S. R.|last2=Pillai|first3=G. E.|last3=Hill|year=2003|title=Chemical warfare? Effects of uropygial oil on feather-degrading bacteria|journal=Journal of Avian Biology|volume=34|pages=345–349|url=http://nature.berkeley.edu/~mshawkey/2.pdf|doi=10.1111/j.0908-8857.2003.03193.x|issue=4|archive-url=https://web.archive.org/web/20080910205855/http://nature.berkeley.edu/~mshawkey/2.pdf|archive-date=10 September 2008}}</ref>

The reds, orange and yellow colors of many feathers are caused by various carotenoids. Carotenoid-based pigments might be honest signals of fitness because they are derived from special diets and hence might be difficult to obtain,<ref>{{cite journal | doi = 10.2307/2408316 | pmid = 28563214 | last1 = Endler | first1 = J. A. | year = 1980 | title = Natural selection on color patterns in Poeci-lia reticulata | jstor = 2408316| journal = Evolution | volume = 34 | issue = 1| pages = 76–91 }}</ref><ref>{{Cite journal|last1= Badyaev |first1=A. V. |last2= Hill |first2= G. E.| year=2000|title=Evolution of sexual dichromatism: contribution of carotenoid versus melanin-based colouration|journal=Biological Journal of the Linnean Society|volume=69|pages=153–172|doi=10.1111/j.1095-8312.2000.tb01196.x|issue=2|s2cid=201965078 |doi-access=free}}</ref> and/or because carotenoids are required for immune function and hence sexual displays come at the expense of health.<ref>{{cite journal | last= Lozano |first= G. A. |s2cid= 86971117 | year = 1994 | title = Carotenoids, parasites, and sexual selection |journal = Oikos | volume = 70 |issue= 2 | pages = 309–311 | doi=10.2307/3545643|jstor= 3545643 |bibcode= 1994Oikos..70..309L }}</ref>

A bird's feathers undergo wear and tear and are replaced periodically during the bird's life through [[molt]]ing. New feathers, known when developing as [[pin feather|blood, or pin feathers]], depending on the stage of growth, are formed through the same follicles from which the old ones were fledged. The presence of melanin in feathers increases their resistance to abrasion.<ref>{{Cite journal|last=Bonser|first=R. H. C.|year=1995|title=Melanin and the abrasion resistance of feathers|jstor=1369048|journal=Condor|url=http://sora.unm.edu/node/105022|volume=97|pages=590–591|doi=10.2307/1369048|issue=2|url-status=live|archive-url=https://web.archive.org/web/20140223002132/https://sora.unm.edu/node/105022|archive-date=23 February 2014|url-access=subscription}}</ref> One study notes that melanin based feathers were observed to degrade more quickly under bacterial action, even compared to unpigmented feathers from the same species, than those unpigmented or with carotenoid pigments.<ref>{{Cite journal|journal=Ardeola|volume=51|issue=2|year=2004|pages=375–383|title=The evolution of bird plumage colouration: A role for feather-degrading bacteria?|last1=Grande|first1=J. M.|last2=Negro|first2=J. J.|first3=M. J.|last3=Torres|url=http://www.ardeola.org/files/Ardeola_51(2)_375-383.pdf|url-status=live|archive-url=https://web.archive.org/web/20080910205855/http://www.ardeola.org/files/Ardeola_51(2)_375-383.pdf|archive-date=10 September 2008}}</ref> However, another study the same year compared the action of bacteria on pigmentations of two song sparrow species and observed that the darker pigmented feathers were more resistant; the authors cited other research also published in 2004 that stated increased melanin provided greater resistance. They observed that the greater resistance of the darker birds confirmed [[Gloger's rule]].<ref>{{Cite journal|last1=Burtt|first1=Edward H. Jr.|last2=Ichida|first2=Jann M.|year=2004|title=Gloger's Rule, feather-degrading bacteria, and color variation among Song Sparrows|journal=Condor|volume=106|issue=3|pages=681–686|doi=10.1650/7383|s2cid=5857742|url=http://www.public.asu.edu/~kjmcgraw/pubs/Condor04b.pdf|url-status=live|archive-url=https://web.archive.org/web/20121120194024/http://www.public.asu.edu/~kjmcgraw/pubs/Condor04b.pdf|archive-date=20 November 2012}}</ref>

Although sexual selection plays a major role in the development of feathers, in particular, the color of the feathers it is not the only conclusion available. New studies are suggesting that the unique feathers of birds are also a large influence on many important aspects of avian behavior, such as the height at which different species build their nests. Since females are the prime caregivers, evolution has helped select females to display duller colors down so that they may blend into the nesting environment. The position of the nest and whether it has a greater chance of being under predation has exerted constraints on female birds' plumage.<ref name="ReferenceA">{{cite journal | last1 = Martin | first1 = T. E. | last2 = Badyaev | first2 = A. V. | year = 1996 | title = Sexual dichromatic in birds; importance of nest predation and nest location for females versus males | journal = Evolution | volume = 50 | issue = 6| pages = 2454–2460 | doi=10.2307/2410712| jstor = 2410712 | pmid = 28565684 }}</ref> A species of bird that nests on the ground, rather than the canopy of the trees, will need to have much duller colors in order not to attract attention to the nest. The height study found that birds that nest in the canopies of trees often have many more predator attacks due to the brighter color of feathers that the female displays.<ref name="ReferenceA"/> Another influence of evolution that could play a part in why feathers of birds are so colorful and display so many patterns could be due to that birds developed their bright colors from the vegetation and flowers that thrive around them. Birds develop their bright colors from living around certain colors. Most bird species often blend into their environment, due to some degree of camouflage, so if the species habitat is full of colors and patterns, the species would eventually evolve to blend in to avoid being eaten. Birds' feathers show a large range of colors, even exceeding the variety of many plants, leaf, and flower colors.<ref>{{cite journal |last1= Caswell Stoddard| first1= Mary | last2= Prum| first2= Richard O. |year=2011 |title=How colorful are birds? Evolution of the avian plumage color gamut |journal=Behavioral Ecology |volume=22 |issue=5 |pages=1042–1052 |doi=10.1093/beheco/arr088 |doi-access=free |hdl=10.1093/beheco/arr088 |hdl-access=free }}</ref>

=== Feathers used in mating displays ===
In sexually dimorphic birds, males often develop distinct coloration or specialized ornamental feathers used in mating displays to attract mates. There are several proposed theories for the origin of ornamental feathers, with the first observed instances being observed in multiple early [[Theropoda|theropods]]<ref name=":1">{{Cite journal |last1=Xu |first1=Xing |last2=Barrett |first2=Paul M. |date=2025-02-19 |title=The origin and early evolution of feathers: implications, uncertainties and future prospects |journal=Biology Letters |volume=21 |issue=2 |pages=20240517 |doi=10.1098/rsbl.2024.0517 |pmc=11837858 |pmid=39969251}}</ref><ref>{{Cite journal |last1=Campione |first1=Nicolás E. |last2=Barrett |first2=Paul M. |last3=Evans |first3=David C. |date=12 March 2020 |title=On the Ancestry of Feathers in Mesozoic Dinosaurs |url=https://link.springer.com/chapter/10.1007/978-3-030-27223-4_12 |journal=The Evolution of Feathers from Their Origin to the Present |series=Fascinating Life Sciences |pages=213–243 |doi=10.1007/978-3-030-27223-4_12 |isbn=978-3-030-27222-7 |via=Springer|url-access=subscription }}</ref> (see subsection on Origins below). 

The most well-known example of ornamental feathers used in mating is male [[Peafowl|peacocks]] (''Pavo cristatus)''. Males sport a long train of covert feathers with distinct eyespot patterns, which are coupled with a vigorous display in the courtship process. When performing these displays, males flash their train in a fanning motion, showing their plumage off to females. 

The evolutionary origin of the peacock’s ornamental feathers and display remains unclear, with multiple theories proposing a combination of factors. In a study observing peacock display behavior, captive male peacocks had the length of their trains, the length of their torsi, and the density of the eyespots measured. They were then released into enclosures with female peacocks, with their mating success measured in successful copulations. The results showed that [[female choice]] was not influenced by train size, but by eyespot density. This suggests that male peacocks’ elaborate feathers and displays evolved as a result of female choice, particularly favoring males with more eyespot patterns<ref>{{Cite journal |last1=Loyau |first1=Adeline |last2=Jalme |first2=Michel Saint |last3=Sorci |first3=Gabriele |date=2005 |title=Intra- and Intersexual Selection for Multiple Traits in the Peacock (Pavo cristatus) |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1439-0310.2005.01091.x |journal=Ethology |language=en |volume=111 |issue=9 |pages=810–820 |doi=10.1111/j.1439-0310.2005.01091.x |bibcode=2005Ethol.111..810L |issn=1439-0310|url-access=subscription }}</ref>. 

==== Structure and use ====
The bone morphology of the radius, ulna, and humerus which support ornamental feathers can also affect female choice<ref name=":2">{{Cite journal |last1=Friscia |first1=Anthony |last2=Sanin |first2=Gloria D. |last3=Lindsay |first3=Willow R. |last4=Day |first4=Lainy B. |last5=Schlinger |first5=Barney A. |last6=Tan |first6=Josh |last7=Fuxjager |first7=Matthew J. |date=2016 |title=Adaptive evolution of a derived radius morphology in manakins (Aves, Pipridae) to support acrobatic display behavior |url=https://onlinelibrary.wiley.com/doi/10.1002/jmor.20534 |journal=Journal of Morphology |language=en |volume=277 |issue=6 |pages=766–775 |doi=10.1002/jmor.20534 |pmid=27027525 |issn=1097-4687|url-access=subscription }}</ref>. For example, the bone morphology of male [[Club-winged manakin|club-winged manakins]] (''Machaeropterus deliciosus'') is highly specialized, with larger and denser ulnas that are bigger in volume and have higher mineral density compared to others in the manakin family<ref name=":2" /><ref>{{Cite journal |last1=Bostwick |first1=Kimberly S. |last2=Riccio |first2=Mark L. |last3=Humphries |first3=Julian M. |date=2012-06-13 |title=Massive, solidified bone in the wing of a volant courting bird |journal=Biology Letters |volume=8 |issue=5 |pages=760–763 |doi=10.1098/rsbl.2012.0382 |pmc=3440988 |pmid=22696286}}</ref>. The secondary feathers are enlarged and are used in mating displays; males knock the tips of the enlarged feathers together repeatedly in a “jump and snap” motion, producing a distinctive sound. The display ends with a “beard up” motion, in which the male shows off their long yellow throat feathers rapidly while performing jumps.

==== Tail Length ====
Tail length is another example of feathers playing a role in mate choice, as seen in the [[long-tailed widowbird]] (''Euplectes progne''). The males of this species have extremely long tail feathers during the mating season, which correlates with higher success in attracting mates<ref name=":3">{{Cite journal |last=Andersson |first=Malte |date=October 1982 |title=Female choice selects for extreme tail length in a widowbird |url=https://www.nature.com/articles/299818a0 |journal=Nature |language=en |volume=299 |issue=5886 |pages=818–820 |doi=10.1038/299818a0 |bibcode=1982Natur.299..818A |issn=1476-4687|url-access=subscription }}</ref>. In a famous study testing the correlation between tail length and [[Fitness (biology)|fitness]], male widowbirds had their tail lengths artificially shortened or elongated and those with elongated tails had higher mating success. It was alternatively proposed that longer ornamental feathers played a role in territory defense and intrasexual competition, as a way of displaying dominance, but there was  no substantial evidence supporting this theory<ref name=":3" />.

==== Origin of ornamental feathers ====
One possible origin of ornamental feathers is in the megalosauroid ''[[Sciurumimus]]'', which have a simple, monofilamentous morphology. Monofilamentous feathers have a single, thread-like structure, as opposed to branches or barbs, and are considered to be the earliest form of feather<ref name=":1" />. Monofilamentous feathers have also been found in a wide range of taxa, though ''Sciurumimus'' was the earliest. Monofilamentous feathers have also been found in the tyrannosauroid ''[[Yutyrannus]]'' and the therizinosauroid ''[[Beipiaosaurus]]'', with proportionally broader monofilaments that were likely a form of early specialized ornamental feathers<ref name=":1" />. 

An analysis of feathers discovered in Burmese [[amber]] revealed unusual coloration along the [[rachis]], suggesting they bore striking color patterns. Early ornamental feathers in the genus ''[[Schizooura]]'' suggest an aerodynamic use as well as an ornamental one, with the pin-tailed shape being too narrow to impact aerodynamics<ref name=":1" />. 

==Parasites==
The feather surface is the home for some ectoparasites, notably feather lice ([[Phthiraptera]]) and feather mites. Feather lice typically live on a single host and can move only from parents to chicks, between mating birds, and, occasionally, by [[phoresy]]. This life history has resulted in most of the parasite species being specific to the host and coevolving with the host, making them of interest in phylogenetic studies.<ref>{{Cite journal|author1=Toon, A. |author2= Hughes, J. |name-list-style=amp|year=2008|title=Are lice good proxies for host history? A comparative analysis of the Australian magpie, ''Gymnorhina tibicen'', and two species of feather louse|journal=Heredity|volume=101|issue=2|pages=127–135|doi=10.1038/hdy.2008.37|pmid=18461081|doi-access=free|bibcode= 2008Hered.101..127T }}</ref>

[[Feather holes]] are chewing traces of lice (most probably ''[[Brueelia]]'' spp. lice) on the wing and tail feathers. They were described on [[barn swallow]]s, and because of easy countability, many evolutionary, ecological, and behavioral publications use them to quantify the intensity of infestation.

Parasitic cuckoos which grow up in the nests of other species also have host-specific feather lice and these seem to be transmitted only after the young cuckoos leave the host nest.<ref>{{Cite journal|author1=Brooke, M. de L.  |author2=Hiroshi Nakamura|year=1998|title=The acquisition of host-specific feather lice by common cuckoos (''Cuculus canorus'')|journal=Journal of Zoology|volume=244|pages=167–173|doi=10.1017/S0952836998002027|issue=2}}</ref>

Birds maintain their feather condition by [[preening]] and bathing in water or [[dust bathing|dust]]. It has been suggested that a peculiar behavior of birds, [[anting (bird activity)|anting]], in which ants are introduced into the plumage, helps to reduce parasites, but no supporting evidence has been found.<ref>{{Cite journal|author1=Revis, Hannah C. |author2=Deborah A. Waller|year=2004|title=Bactericidal and fungicidal activity of ant chemicals on feather parasites: an evaluation of anting behavior as a method of self-medication in songbirds| journal=Auk|volume=121|issue=4|pages=1262–1268|doi=10.1642/0004-8038(2004)121[1262:BAFAOA]2.0.CO;2|s2cid=85677766 |doi-access=free}}</ref>

==Human usage==

===Utilitarian ===
[[File:Fully feathered basket Santa Roas College.jpg|thumb|[[Pomo]] [[fully feathered basket]] curated at the Jesse Peter Multicultural Museum, Santa Rosa College]]
[[File:Female model with feathers.jpg|thumb|Female model with feathers]]
Bird feathers have long been used for [[fletching]] [[arrow (weapon)|arrows]]. Colorful feathers such as those belonging to [[pheasant]]s have been used to decorate [[fishing lure]]s.

Feathers are also valuable in aiding the identification of species in forensic studies, particularly in [[bird strike]]s to aircraft. The ratios of hydrogen isotopes in feathers help in determining the geographic origins of birds.<ref>{{Cite journal|journal=Oecologia|title=Global application of stable hydrogen and oxygen isotopes to wildlife forensics|volume=143|issue=3|pages=337–348|doi=10.1007/s00442-004-1813-y|year=2005|pmid=15726429|author1=Bowen, Gabriel J|author2=Wassenaar, Leonard I|author3=Hobson, Keith A|bibcode=2005Oecol.143..337B|s2cid=1762342}}</ref> Feathers may also be useful in the non-destructive sampling of pollutants.<ref>{{Cite journal|author1=Jaspers, V. |author2=Voorspoels, S. |author3=Covaci, A. |author4=Lepoint, G. |author5= Eens, M. |name-list-style=amp|year=2007|title=Evaluation of the usefulness of bird feathers as a non-destructive biomonitoring tool for organic pollutants: A comparative and meta-analytical approach|journal=Environment International|volume=33|issue=3|pages=328–337|doi=10.1016/j.envint.2006.11.011|pmid=17198730|bibcode=2007EnInt..33..328J |hdl=2268/1067 |url=http://orbi.ulg.ac.be/handle/2268/1067 |hdl-access=free}}</ref>

The poultry industry produces a large amount of feathers as waste, which, like other forms of keratin, are slow to decompose. Feather waste has been used in a number of industrial applications as a medium for culturing microbes,<ref>{{Cite journal|title=Use of feather-based culture media for the production of mosquitocidal bacteria|doi=10.1016/j.biocontrol.2007.04.019|journal=Biological Control|volume=43|issue=1|pages=49–55|author1=Poopathi, S.  |author2=Abidha, S.|year=2007|bibcode=2007BiolC..43...49P }}</ref> biodegradable polymers,<ref>{{Cite conference |author1=Schmidt, W.F. |author2=Barone, J.R. |year=2004|contribution=New uses for chicken feathers keratin fiber |title=Poultry Waste Management Symposium Proceedings|pages=99–101 |url=https://www.ars.usda.gov/research/publications/publication/?seqNo115=170632}}</ref> and production of enzymes.<ref>{{Cite journal|journal=Food and Bioprocess Technology|title=Use of Poultry Byproduct for Production of Keratinolytic Enzymes|volume=1|issue=3|pages=301–305|year=2008|doi=10.1007/s11947-008-0091-9|author1=Casarin, Franciani|author2=Brandelli, Florencia Cladera-Olivera Adriano|last3=Brandelli|first3=Adriano|s2cid=96154497}}</ref> Feather proteins have been tried as an adhesive for wood board.<ref>{{Cite journal|author1=Jiang, Z.|author2=Qin, D.|author3=Hse, C.|author4=Kuo, M.|author5=Luo, Z.|author6=Wang, G.|year=2008|title=Preliminary Study on Chicken Feather Protein-Based Wood Adhesives|url=http://www.srs.fs.usda.gov/pubs/33607|journal=Journal of Wood Chemistry & Technology|volume=28|issue=3|pages=240–246|doi=10.1080/02773810802347073|s2cid=3656808|display-authors=etal|url-status=live|archive-url=https://web.archive.org/web/20140219195609/http://www.srs.fs.usda.gov/pubs/33607|archive-date=19 February 2014|url-access=subscription}}</ref>

Some groups of Native people in Alaska have used ptarmigan feathers as temper (non-plastic additives) in pottery manufacture since the first millennium BC in order to promote thermal shock resistance and strength.<ref>Neusius, Sarah W. and G. Timothy Gross
2007 Seeking Our Past: An Introduction to North American Archaeology.  Oxford University Press, NY.
</ref>

===In religion and culture===
[[File: San Isidro labrador.jpg|thumb|left|[[Mexican featherwork]] painting of [[Isidore the Laborer]] made from duck, hummingbird, and canary feathers. This style of painting, popular during the [[New Spain|Novohispanic]] era, integrates featherwork of pre-Hispanic origin with Christian iconography. 18th century, [[Museo Soumaya]]]]
[[Eagle]] feathers have great cultural and spiritual value to [[Native Americans in the United States|Native Americans]] in the [[United States]] and [[First Nations in Canada|First Nations]] peoples in [[Canada]] as religious objects. In the United States, the religious use of eagle and [[hawk]] feathers is governed by the [[eagle feather law]], a federal law limiting the possession of eagle feathers to certified and enrolled members of federally recognized Native American tribes.

In South America, brews made from the feathers of [[condor]]s are used in traditional medications.<ref>{{Cite journal|first= Steve |last=Froemming|title=Traditional use of the Andean flicker (Colaptes rupicola) as a galactagogue in the Peruvian Andes|journal=Journal of Ethnobiology and Ethnomedicine| year=2006|volume=2|page=23 |doi=10.1186/1746-4269-2-23|pmid=16677398|pmc=1484469 |doi-access=free }}</ref> In India, feathers of the [[Indian peacock]] have been used in traditional medicine for snakebite, infertility, and coughs.<ref>{{Cite journal|last1= Murari| first1= S.K.|last2= Frey|first2= F.J.|last3= Frey|first3= B.M.|last4= Gowda|first4= T.V.|last5= Vishwanath|first5= B.S.|year=2005|title=Use of ''Pavo cristatus'' feather extract for the better management of snakebites: Neutralization of inflammatory reactions|journal=Journal of Ethnopharmacology|volume=99|issue=2|pages=229–237|doi=10.1016/j.jep.2005.02.027|pmid=15894132}}</ref><ref>{{Cite journal|title=Traditional knowledge on zootherapeutic uses by the Saharia tribe of Rajasthan, India|last1= Mahawar |first1=M. M. | last2=Jaroli |first2=D. P. |journal=Journal of Ethnobiology and Ethnomedicine|year=2007|volume=3|page=25|doi=10.1186/1746-4269-3-25| pmid= 17547781|pmc=1892771 |doi-access= free }}</ref>

Members of Scotland's [[Clan Campbell]] are known to wear feathers on their bonnets to signify authority within the clan. [[Scottish clan chief|Clan chiefs]] wear three, chieftains<!--How does this differ from clan chief?--> wear two and an [[armiger]] wears one. Any member of the clan who does not meet the criteria is not authorized to wear feathers as part of traditional garb and doing so is considered presumptuous.<ref>{{cite web |title=Scottish Highland Dress: Clan Campbell |url= https://www.ccsna.org/scottish-highland-dress#NO%20FEATHERS%20IN%20YOUR%20CAP |publisher=Clan Campbell Society |access-date=10 November 2020}}</ref>

During the 18th, 19th, and early 20th centuries, there was a booming international trade in plumes for extravagant women's hats and other headgear (including in [[Victorian fashion]]). [[Frank Chapman (ornithologist)|Frank Chapman]] noted in 1886 that feathers of as many as 40 species of birds were used in about three-fourths of the 700 ladies' hats that he observed in New York City.<ref>Doughty, Robin W. ''Feather Fashions and Bird Preservation, A Study in Nature Protection''. University of California Press. Page 197.</ref> For instance, South American [[hummingbird]] feathers were used in the past to dress some of the miniature birds featured in [[singing bird box]]es. This trade caused severe losses to bird populations (for example, [[egret]]s and [[whooping crane]]s). 

Conservationists led campaigns against the use of feathers in hats, contributing to important measures for environmental protection and to changes in fashion. Examples are the creation of the [[Royal Society for the Protection of Birds]] in the UK in 1889, or the passage of the [[Lacey Act]] in USA in 1900,  The ornamental feather market then largely collapsed.<ref>{{cite web| last1= Ehrlich| first1= Paul R.| last2= Dobkin| first2= David S.| last3= Wheye| first3= Darryl| year= 1988| url= http://www.stanford.edu/group/stanfordbirds/text/essays/Plume_Trade.html| title= Plume Trade| publisher= Stanford University| url-status= live| archive-url= https://web.archive.org/web/20080930070559/http://www.stanford.edu/group/stanfordbirds/text/essays/Plume_Trade.html| archive-date= 30 September 2008}}</ref><ref>[http://americanhistory.si.edu/feather/ftfa.htm Feather trade] {{webarchive|url=https://web.archive.org/web/20080623044023/http://americanhistory.si.edu/feather/ftfa.htm |date=23 June 2008 }}, Smithsonian Institution</ref>

More recently, rooster plumage has become a popular trend as a [[hairstyle]] accessory, with feathers formerly used as fishing lures now being used to provide color and style to hair.<ref>{{cite news | url=http://seattletimes.nwsource.com/html/outdoors/2015246435_flyfash.html | work=The Seattle Times | first=Jessie L. | last=Bonner | title=High fashion or bait? Fly ties now hair extensions | date=6 June 2011 | url-status=live | archive-url=https://web.archive.org/web/20110610110027/http://seattletimes.nwsource.com/html/outdoors/2015246435_flyfash.html | archive-date=10 June 2011 }}</ref>

Feather products manufacturing in Europe has declined in the last 60 years, mainly due to competition from Asia.
Feathers have adorned hats at many prestigious events such as weddings and Ladies Day at racecourses (Royal Ascot).

==Evolution==
{{Main|Origin of avian flight}}
{{multiple image
 | align     = right
 | direction = parallel
 | image1    = Archaeopteryx (Feather).jpg
 | width1    = 150
 | caption1  = [[Late Jurassic]] fossil feather of an unidentified dinosaur, once thought to be ''[[Archaeopteryx]]''.<!--although this feather was given the name 'Archaeopteryx', in turns out to be non-avian. See Archaeopteryx article.-->
 | image2    = Rachis-dominated feathers Burmese amber NMNS.jpg
 | width2    = 150
 | caption2  = Rachis-dominated feathers inside mid-[[Cretaceous]] [[Burmese amber]]
}}
=== Functional considerations ===
The functional view on the evolution of feathers has traditionally focused on insulation, flight and display. Discoveries of non-flying Late Cretaceous feathered dinosaurs in China,<ref name="NYT-20161208">{{cite news |last=St. Fleur |first=Nicholas |title=That Thing With Feathers Trapped in Amber? It Was a Dinosaur Tail |url=https://www.nytimes.com/2016/12/08/science/dinosaur-feathers-amber.html |date=8 December 2016 |work=[[The New York Times]] |access-date=8 December 2016 |url-status=live |archive-url=https://web.archive.org/web/20161208224540/http://www.nytimes.com/2016/12/08/science/dinosaur-feathers-amber.html |archive-date=8 December 2016 }}</ref> however, suggest that flight could not have been the original primary function as the feathers simply would not have been capable of providing any form of lift.<ref name="sumida">{{Cite journal|author1=Sumida, SS|author2=CA Brochu|year=2000|title=Phylogenetic context for the origin of feathers|doi=10.1093/icb/40.4.486|journal=American Zoologist|volume=40|issue=4|pages=486–503|doi-access=free}}</ref><ref>{{Cite journal|author1=Dimond, C. C. |author2=R. J. Cabin |author3=J. S. Brooks |journal=BIOS|title=Feathers, Dinosaurs, and Behavioral Cues: Defining the Visual Display Hypothesis for the Adaptive Function of Feathers in Non-Avian Theropods | volume=82|year=2011|pages=58–63 | doi=10.1893/011.082.0302|issue=3|s2cid=98221211}}</ref> There have been suggestions that feathers may have had their original function in thermoregulation, waterproofing, or even as sinks for metabolic wastes such as sulphur.<ref>{{cite journal| title= Explanatory History of the Origin of Feathers|author=Bock, WJ|year=2000| journal= Am. Zool.|volume=40 |issue=4|pages=478–485 |doi=10.1093/icb/40.4.478|doi-access=free}}</ref> [[Yutyrannus|Recent discoveries]] are argued to support a thermoregulatory function, at least in smaller dinosaurs.<ref>{{Cite journal |date=4 April 2012 |author=Whitfield, John |title=Largest feathered dinosaur yet discovered in China |journal=Nature News Blog |url=http://blogs.nature.com/news/2012/04/largest-feathered-dinosaur-discovered-in-china.html |access-date=4 April 2012 |url-status=live |archive-url=https://web.archive.org/web/20120406145618/http://blogs.nature.com/news/2012/04/largest-feathered-dinosaur-discovered-in-china.html |archive-date=6 April 2012 }}</ref><ref name="yutyrannus">{{cite journal |author1=Xu X. |author2=Wang K. |author3=Zhang K. |author4=Ma Q. |author5=Xing L. |author6=Sullivan C. |author7=Hu D. |author8=Cheng S. |author9=Wang S. |year=2012 |title=A gigantic feathered dinosaur from the Lower Cretaceous of China |url=http://www.xinglida.net/pdf/Xu_et_al_2012_Yutyrannus.pdf |journal=Nature |volume=484 |issue=7392 |pages=92–95 |doi=10.1038/nature10906 |pmid=22481363 |bibcode=2012Natur.484...92X |s2cid=29689629 |display-authors=etal |archive-url=https://web.archive.org/web/20120417134949/http://www.xinglida.net/pdf/Xu_et_al_2012_Yutyrannus.pdf |archive-date=17 April 2012 }}</ref> Some researchers even argue that thermoregulation arose from bristles on the face that were used as tactile sensors.<ref>{{Cite journal|last1=Persons|first1=Walter S.|last2=Currie|first2=Philip J.|date=2015|title=Bristles before down: A new perspective on the functional origin of feathers|journal=Evolution|language=en|volume=69|issue=4|pages=857–862|doi=10.1111/evo.12634|issn=1558-5646|pmid=25756292|s2cid=24319963|doi-access=free}}</ref> While feathers have been suggested as having evolved from reptilian [[scale (zoology)|scales]], there are numerous objections to that idea, and more recent explanations have arisen from the paradigm of [[evolutionary developmental biology]].<ref name="Prum2003" /> Theories of the scale-based origins of feathers suggest that the planar scale structure was modified for development into feathers by splitting to form the webbing; however, that developmental process involves a tubular structure arising from a follicle and the tube splitting longitudinally to form the webbing.<ref name="Prum2002" /><ref name="Prum2003" /> The number of feathers per unit area of skin is higher in smaller birds than in larger birds, and this trend points to their important role in thermal insulation, since smaller birds lose more heat due to the relatively larger surface area in proportion to their body weight.<ref name="pettingill" /> The miniaturization of birds also played a role in the evolution of powered flight.<ref>{{Cite journal|author1=De Ricqles |author2=A. J. |author3=K. Padian |author4=J. R. Horner |author5=E. T. Lamm |author6=N. Myhrvold |year=2003|title=Osteohistology of confuciusornis sanctus (theropoda: Aves)|journal=Journal of Vertebrate Paleontology|volume=23|issue=2 |pages=373–386|doi=10.1671/0272-4634(2003)023[0373:oocsta]2.0.co;2 |s2cid=84936431 }}</ref> The coloration of feathers is believed to have evolved primarily in response to [[sexual selection]]. In fossil specimens of the [[Paraves|paravian]] ''[[Anchiornis huxleyi]]'' and the [[pterosaur]] ''[[Tupandactylus imperator]]'', the features are so well preserved that the [[melanosome]] (pigment cells) structure can be observed. By comparing the shape of the fossil melanosomes to melanosomes from extant birds, the color and pattern of the feathers on ''Anchiornis'' and ''Tupandactylus'' could be determined.<ref>{{cite journal|last1=Li|first1=Quanguo|last2=Gao|first2=Ke-Qin|last3=Vinther|first3=Jakob|last4=Shawkey|first4=Matthew|last5=Clarke|first5=Julia|last6=D'Alba|first6=Liliana|last7=Meng|first7=Qingjin|last8=Briggs|first8=Derek|last9=Prum|first9=Richard|title=Plumage Color Patterns of an Extinct Dinosaur|journal=Science|date=12 March 2010|volume=327|issue=5971|pages=1369–1372|doi=10.1126/science.1186290|pmid=20133521|bibcode = 2010Sci...327.1369L |s2cid=206525132|url=http://doc.rero.ch/record/210394/files/PAL_E4402.pdf}}</ref><ref>Cincotta, A., Nicolaï, M., Campos, H.B.N. et al. Pterosaur melanosomes support signalling functions for early feathers. Nature 604, 684–688 (2022). {{doi|10.1038/s41586-022-04622-3}}.</ref> ''Anchiornis'' was found to have black-and-white-patterned feathers on the forelimbs and hindlimbs, with a reddish-brown crest. This pattern is similar to the coloration of many extant bird species, which use plumage coloration for display and communication, including sexual selection and camouflage. It is likely that non-avian dinosaur species utilized plumage patterns for similar functions as modern birds before the origin of flight. In many cases, the physiological condition of the birds (especially males) is indicated by the quality of their feathers, and this is used (by the females) in [[mate choice]].<ref>{{Cite journal|author1=Saino, Nicola |author2=Riccardo Stradi|s2cid=4400888|year=1999|title=Carotenoid Plasma Concentration, Immune Profile, and Plumage Ornamentation of Male Barn Swallows|journal=American Naturalist|volume=154|issue=4|pages=441–448|doi=10.1086/303246|pmid=10523490}}</ref><ref>{{Cite journal|author1=Endler, John A. |author2=David A. Westcott |author3= Joah R. Madden |author4=Tim Robson |author5= Patrick Phillips  |name-list-style=amp |year=2005|title=Animal visual systems and the evolution of color patterns: Sensory processing illumiates signal evolution|journal=Evolution|volume=59|issue=8|pages=1795–1818|pmid=16329248|doi=10.1111/j.0014-3820.2005.tb01827.x|s2cid=25683790 |doi-access=free}}</ref> Additionally, when comparing different ''[[Ornithomimus|Ornithomimus edmontonicus]]'' specimens, older individuals were found to have a pennibrachium (a wing-like structure consisting of elongate feathers), while younger ones did not. This suggests that the pennibrachium was a secondary sex characteristic and likely had a sexual function.<ref>{{Cite journal|last1=Zelenitsky|first1=D. K.|last2=Therrien|first2=F.|last3=Erickson|first3=G. M.|last4=DeBuhr|first4=C. L.|last5=Kobayashi|first5=Y.|last6=Eberth|first6=D. A.|last7=Hadfield|first7=F.|date=2012-10-26|title=Feathered Non-Avian Dinosaurs from North America Provide Insight into Wing Origins|journal=Science|language=en|volume=338|issue=6106|pages=510–514|doi=10.1126/science.1225376|pmid=23112330|issn=0036-8075|bibcode=2012Sci...338..510Z|s2cid=2057698}}</ref>

=== Molecular evolution ===
Several [[gene]]s have been found to determine feather development. They will be key to understand the evolution of feathers. For instance, some genes convert scales into feathers or feather-like structures when expressed or induced in bird feet, such as the scale-feather converters [[SOX2|Sox2]], [[ZIC1|Zic1]], [[Gremlin (protein)|Grem1]], [[SPRY2|Spry2]], and [[SOX18|Sox18]].<ref>{{Cite journal|last1=Wu|first1=Ping|last2=Yan|first2=Jie|last3=Lai|first3=Yung-Chih|last4=Ng|first4=Chen Siang|last5=Li|first5=Ang|last6=Jiang|first6=Xueyuan|last7=Elsey|first7=Ruth M.|last8=Widelitz|first8=Randall|last9=Bajpai|first9=Ruchi|last10=Li|first10=Wen-Hsiung|last11=Chuong|first11=Cheng-Ming|date=2018-02-01|title=Multiple Regulatory Modules Are Required for Scale-to-Feather Conversion|journal=Molecular Biology and Evolution|volume=35|issue=2|pages=417–430|doi=10.1093/molbev/msx295|issn=1537-1719|pmc=5850302|pmid=29177513}}</ref>

Feathers and scales are made up of two distinct forms of [[keratin]], and it was long thought that each type of keratin was exclusive to each skin structure (feathers and scales). However, feather keratin is also present in the early stages of development of [[American alligator]] scales. This type of keratin, previously thought to be specific to feathers, is suppressed during embryological development of the alligator and so is not present in the scales of mature alligators. The presence of this [[Homology (biology)|homologous]] keratin in both birds and [[crocodilian]]s indicates that it was inherited from a common ancestor.<ref>{{Cite journal |last1=Alibardi |first1=L. |last2=Knapp |first2=L. W. |last3=Sawyer |first3=R. H. |date=June 2006 |title=Beta-keratin localization in developing alligator scales and feathers in relation to the development and evolution of feathers |url=https://www.researchgate.net/publication/6055177 |journal=Journal of Submicroscopic Cytology and Pathology |volume=38 |issue=2–3 |pages=175–192 |issn=1122-9497 |pmid=17784647}}</ref>

This may suggest that crocodilian scales, bird and dinosaur feathers, and pterosaur [[pycnofibre]]s are all developmental expressions of the same primitive archosaur skin structures; suggesting that feathers and pycnofibers could be homologous.<ref>{{cite journal |last1=Alibardi |first1=L |last2=Knapp |first2=LW |last3=Sawyer |first3=RH |year=2006 |title=Beta-keratin localization in developing alligator scales and feathers in relation to the development and evolution of feathers |url=https://www.researchgate.net/publication/6055177 |journal=Journal of Submicroscopic Cytology and Pathology |volume=38 |issue=2–3 |pages=175–92 |pmid=17784647}}</ref> Molecular dating methods in 2011 show that the subfamily of feather β-keratins found in extant birds started to diverge 143 million years ago, suggesting the pennaceous feathers of ''Anchiornis'' were not made of the feather β-keratins present in extant birds.<ref>{{Cite journal |last1=Greenwold |first1=Matthew J. |last2=Sawyer |first2=Roger H. |date=2011-12-15 |title=Linking the molecular evolution of avian beta (β) keratins to the evolution of feathers |url=https://d1wqtxts1xzle7.cloudfront.net/50801629/jez.b.2143620161209-26901-9mlb8t-with-cover-page-v2.pdf?Expires=1665801383&Signature=gJjg-n6ADk7cVZ2dpCUno4Q8X~l2ixG6T8NxcOwJxsDy1RgCxwvNv2UpiHylOeKMuq2TBU~~W0gxtieZHVMOjC1bQONwqdlg0xcNkKIvNXoGxrr7tRZ5J2DfxrJ-3JsT~Uns8SZ1ry8wBbv5V0Hz1etiFG4nPqs5Yx4b0D9xS2vVr~wIcqed8x84xspBlysJjavqztbFOLKPfGN7x9ez~L4sno3CogZU9bVpqD6Zq~w53esghZrWV5VQCw25je43qNFiWixHAi~aeFRpLP0IiiTFJc64XpHEiAMlu4Buh4ypOdP1z7Imnnc-bj3opJ1FSbM3VizRyqxdvDrNOMsEMw__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA |journal=Journal of Experimental Zoology Part B: Molecular and Developmental Evolution |language=en |volume=316B |issue=8 |pages=609–616 |doi=10.1002/jez.b.21436 |pmid=21898788 |bibcode=2011JEZB..316..609G |access-date=15 October 2022 |archive-date=15 October 2022 |archive-url=https://web.archive.org/web/20221015014225/https://d1wqtxts1xzle7.cloudfront.net/50801629/jez.b.2143620161209-26901-9mlb8t-with-cover-page-v2.pdf?Expires=1665801383&Signature=gJjg-n6ADk7cVZ2dpCUno4Q8X~l2ixG6T8NxcOwJxsDy1RgCxwvNv2UpiHylOeKMuq2TBU~~W0gxtieZHVMOjC1bQONwqdlg0xcNkKIvNXoGxrr7tRZ5J2DfxrJ-3JsT~Uns8SZ1ry8wBbv5V0Hz1etiFG4nPqs5Yx4b0D9xS2vVr~wIcqed8x84xspBlysJjavqztbFOLKPfGN7x9ez~L4sno3CogZU9bVpqD6Zq~w53esghZrWV5VQCw25je43qNFiWixHAi~aeFRpLP0IiiTFJc64XpHEiAMlu4Buh4ypOdP1z7Imnnc-bj3opJ1FSbM3VizRyqxdvDrNOMsEMw__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA |url-status=dead }}</ref> However, a study of fossil feathers from the dinosaur Sinosauropteryx and other fossils revealed traces of beta-sheet proteins, using infrared spectroscopy and sulfur-X-ray spectroscopy. The presence of abundant alpha-proteins in some fossil feathers was shown to be an artefact of the fossilization process, as beta-protein structures are readily altered to alpha-helices during thermal degradation.<ref>{{cite journal |last1=Slater |first1=Tiffany S |last2=Edwards |first2=Nicholas P |last3=Webb |first3=Samuel M |last4=Zhang |first4=Fucheng |last5=McNamara |first5=Maria E |title=Preservation of corneous β-proteins in Mesozoic feathers |journal=Nature Ecology & Evolution |date=2023 |volume=7 |issue=10 |pages=1706–1713 |doi=10.1038/s41559-023-02177-8 |pmid=37735563 |bibcode=2023NatEE...7.1706S |osti=2327098 |s2cid=262125827 |url=https://www.nature.com/articles/s41559-023-02177-8}}</ref> In 2019, scientists found that genes for the production of feathers evolved at the base of archosauria, supporting that feathers were present at early ornithodirans and is consistent with the fossil record.<ref name=":0">{{Cite journal |last1=Benton |first1=Michael J. |last2=Dhouailly |first2=Danielle |last3=Jiang |first3=Baoyu |last4=McNamara |first4=Maria |date=2019-09-01 |title=The Early Origin of Feathers |url=https://cora.ucc.ie/bitstream/handle/10468/8068/10285.pdf?sequence=1 |journal=Trends in Ecology & Evolution |language=en |volume=34 |issue=9 |pages=856–869 |doi=10.1016/j.tree.2019.04.018 |pmid=31164250 |bibcode=2019TEcoE..34..856B |hdl=10468/8068 |s2cid=174811556 |issn=0169-5347}}</ref>

===Feathered dinosaurs===
{{Main|Feathered dinosaurs}}
[[File:Archaeopteryx lithographica (Berlin specimen).jpg|thumb|left|upright|''[[Archaeopteryx lithographica]]'' (Berlin specimen)]]
Several non-avian [[feathered dinosaurs|dinosaurs]] had feathers on their limbs that would not have functioned for flight.<ref name="NYT-20161208" /><ref name=Prum2003/> One theory suggests that feathers originally evolved on dinosaurs due to their [[Thermal insulation|insulation]] properties; then, small dinosaur species which grew longer feathers may have found them helpful in gliding, leading to the evolution of proto-birds like ''[[Archaeopteryx]]'' and ''[[Microraptor]] zhaoianus''. Another theory posits that the original adaptive advantage of early feathers was their pigmentation or iridescence, contributing to sexual preference in mate selection.<ref>
{{Cite journal|author1=Dimond, C. C. |author2=R. J. Cabin |author3=J. S. Brooks |journal=BIOS
|title=Feathers, Dinosaurs, and Behavioral Cues: Defining the Visual Display Hypothesis for the Adaptive Function of Feathers in Non-Avian Theropods|volume=82|year=2011|pages=58–63|doi=10.1893/011.082.0302|issue=3|s2cid=98221211
}}
</ref> Dinosaurs that had feathers or protofeathers include ''[[Pedopenna]] daohugouensis''<ref>
{{Cite journal|journal= Naturwissenschaften|title=A new maniraptoran dinosaur from China with long feathers on the metatarsus|volume=92|issue=4|pages=173–177|author1=Xu, Xing  |author2=Fucheng Zhang|doi=10.1007/s00114-004-0604-y|year= 2005|pmid= 15685441|bibcode=2005NW.....92..173X|s2cid=789908}}
</ref> and ''[[Dilong paradoxus]]'', a [[tyrannosauroid]] which is 60 to 70 million years older than ''[[Tyrannosaurus|Tyrannosaurus rex]].''<ref>
{{Cite journal|author=Xu, Xing|s2cid=1516713|title=Feathered dinosaurs from China and the evolution of major avian characters|journal=Integrative Zoology|volume=1|issue=1|pages=4–11|year=2006|doi=10.1111/j.1749-4877.2006.00004.x|pmid=21395983|doi-access=free}}</ref>

The majority of dinosaurs known to have had feathers or protofeathers are [[Theropoda|theropods]], however featherlike "filamentous integumentary structures" are also known from the [[ornithischian]] dinosaurs ''[[Tianyulong]]'' and ''[[Psittacosaurus]]''.<ref>{{Cite journal|author1=Zheng, X. T. |author2=H. L. You |author3= X. Xu |author4= Z. M. Dong |name-list-style=amp |journal=Nature|title=An Early Cretaceous heterodontosaurid dinosaur with filamentous integumentary structures|volume=458|year=2009|pages=333–336|doi=10.1038/nature07856|pmid=19295609|issue=7236|bibcode = 2009Natur.458..333Z |s2cid=4423110 }}</ref> The exact nature of these structures is still under study. However, it is believed that the stage-1 feathers (see [[Feather#Evolutionary stages|Evolutionary stages]] section below) such as those seen in these two ornithischians likely functioned in display.<ref name="xu&guo2009"/> In 2014, the ornithischian ''[[Kulindadromeus]]'' was reported as having structures resembling stage-3 feathers.<ref name="Godefroit2014" /> The likelihood of scales evolving on early dinosaur ancestors are high. However, this was by assuming that primitive pterosaurs were scaly.<ref>{{Cite journal|last1=Barrett|first1=Paul M.|last2=Evans|first2=David C.|last3=Campione|first3=Nicolás E.|date=2015-06-30|title=Evolution of dinosaur epidermal structures|journal=Biology Letters|volume=11|issue=6|page=20150229|doi=10.1098/rsbl.2015.0229|pmc=4528472|pmid=26041865}}</ref><ref name="youtube.com">{{Citation|title=Those feathers won't stick: maximum likelihood modelling supports scales as primitive for Dinosauria (The 66th Symposium on Vertebrate Palaeontology and Comparative Anatomy)|url=https://www.youtube.com/watch?v=2MOCbXPwshA| archive-url=https://ghostarchive.org/varchive/youtube/20211211/2MOCbXPwshA| archive-date=2021-12-11 | url-status=live|publication-date=November 9, 2018|language=en|access-date=2021-10-03}}{{cbignore}}</ref> A 2016 study analyzes the pulp morphology of the tail bristles of ''Psittacosaurus'' and finds they are similar to feathers but notes that they are also similar to the bristles on the head of the [[Congo peafowl]], the beard of the [[Turkey (bird)|turkey]], and the spine on the head of the [[horned screamer]].<ref>{{Cite journal |last1=Mayr |first1=Gerald |last2=Pittman |first2=Michael |last3=Saitta |first3=Evan |last4=Kaye |first4=Thomas G. |last5=Vinther |first5=Jakob |date=August 30, 2016 |editor-last=Benson |editor-first=Roger |title=Structure and homology of Psittacosaurus tail bristles |url=https://onlinelibrary.wiley.com/doi/10.1111/pala.12257 |journal=Palaeontology |language=en |volume=59 |issue=6 |pages=793–802 |doi=10.1111/pala.12257|bibcode=2016Palgy..59..793M |hdl=1983/029c668f-08b9-45f6-a0c5-30ce9256e593 |s2cid=89156313 |hdl-access=free }}</ref> A reestimation of maximum likelihoods by paleontologist [[Thomas R. Holtz Jr.|Thomas Holtz]] finds that filaments were more likely to be the ancestral state of dinosaurs.<ref>{{Cite web |last=Holtz |first=Thomas |date=2018-10-19 |title="Integumentary Status: It's Complicated': Phylogenetic, Sedimentary, and Biological Impediments to Resolving the Ancestral Integument of Mesozoic Dinosauria |url=https://vertpaleo.org/wp-content/uploads/2021/03/SVP-2018-program-book-V4-FINAL-with-covers-9-24-18.pdf |access-date=2022-07-16 |website=Society of Vertebrate Paleontology |language=en-US}}</ref>

In 2010, a [[Carcharodontosauridae|carcharodontosaurid]] named [[Concavenator|''Concavenator corcovatus'']] was found to have [[Flight feather#Remiges|remiges]] on the ulna suggesting it might have had quill-like structures on the ams.<ref>{{Cite journal|last1=Ortega|first1=Francisco|last2=Escaso|first2=Fernando|last3=Sanz|first3=José L.|date=September 9, 2010|title=A bizarre, humped Carcharodontosauria (Theropoda) from the Lower Cretaceous of Spain|url=https://www.nature.com/articles/nature09181|journal=Nature|language=en|volume=467|issue=7312|pages=203–206|doi=10.1038/nature09181|pmid=20829793|bibcode=2010Natur.467..203O|s2cid=4395795|issn=1476-4687|url-access=subscription}}</ref> However, Foth et al. 2014 disagress with the publication where they point out that the bumps on the ulna of ''Concavenator'' are on the [[Anatomical terms of location#Main terms|anterolateral]] which is unlike remiges which are in a [[Anatomical terms of location#Main terms|posterolateral]] on the ulna of some birds, they consider it more likely that these are attachments for interosseous ligaments.<ref>{{Cite journal|last1=Foth|first1=Christian|last2=Tischlinger|first2=Helmut|last3=Rauhut|first3=Oliver W.M.|date=2014-06-02|title=New specimen of Archaeopteryx provides insights into the evolution of pennaceous feathers|url=https://www.nature.com/articles/nature13467|journal=Nature|volume=511|issue=7507|pages=79–82|doi=10.1038/nature13467|pmid=24990749|bibcode=2014Natur.511...79F|s2cid=4464659|url-access=subscription}}</ref> This was refuted by Cuesta Fidalgo and her colleagues, they pointed out that these bumps on the ulna are posterolateral which is unlike that of interosseous ligaments.<ref>{{Cite journal |last1=Cuesta |first1=Elena |last2=Ortega |first2=Francisco |last3=Sanz |first3=José Luis |date=2018-07-04 |title=Appendicular osteology of Concavenator corcovatus (Theropoda: Carcharodontosauridae) from the Lower Cretaceous of Spain |journal=Journal of Vertebrate Paleontology |volume=38 |issue=4 |pages=(1)–(24) |doi=10.1080/02724634.2018.1485153 |s2cid=91976402 |issn=0272-4634|url=https://figshare.com/articles/journal_contribution/7177802 |url-access=subscription }}</ref>

Since the 1990s, dozens of feathered dinosaurs have been discovered in the clade [[Maniraptora]], which includes the clade Avialae and the recent common ancestors of birds, [[Oviraptorosauria]] and [[Deinonychosauria]]. In 1998, the discovery of a feathered oviraptorosaurian, ''Caudipteryx zoui'', challenged the notion of feathers as a structure exclusive to Avialae.<ref>{{Cite journal|doi=10.1038/31635 |author=Ji, Q. |author2=P. J. Currie |author3=M. A. Norell |author4=S. A. Ji
|title=Two feathered dinosaurs from northeastern China |journal=Nature |volume=393 |year=1998 |pages=753–761
|issue=6687|bibcode = 1998Natur.393..753Q |s2cid=205001388
|url=http://doc.rero.ch/record/31829/files/PAL_E1436.pdf
}}
</ref> Buried in the Yixian Formation in Liaoning, China, ''C. zoui'' lived during the Early Cretaceous Period. Present on the forelimbs and tails, their integumentary structure has been accepted{{by whom|date=April 2014}} as pennaceous vaned feathers based on the rachis and herringbone pattern of the barbs. In the clade Deinonychosauria, the continued divergence of feathers is also apparent in the families [[Troodontidae]] and [[Dromaeosauridae]]. Branched feathers with rachis, barbs, and barbules were discovered in many members including ''Sinornithosaurus millenii'', a dromaeosaurid found in the Yixian formation (124.6 MYA).<ref>
{{Cite journal|doi=10.1038/35065589 |author1=Xu, X. |author2=H. H. Zhou |author3= R. O. Prum  |name-list-style=amp |title=Branched integumental structures in Sinornithosaurus and the origin of feathers |journal=Nature |volume=410
|issue=6825 |year=2001 |pages=200–204 |pmid=11242078 |bibcode=2001Natur.410..200X |s2cid=4426803 }}</ref>

Previously, a temporal paradox existed in the evolution of feathers—theropods with highly derived bird-like characteristics occurred at a later time than ''[[Archaeopteryx]]''—suggesting that the descendants of birds arose before the ancestor. However, the discovery of ''Anchiornis huxleyi'' in the Late Jurassic Tiaojishan Formation (160 MYA) in western Liaoning in 2009<ref>
{{Cite journal |author=Hu, D. Y. |author2=L. H. Hou |author3=L. J. Zhang |author4=X. Xu
|title=A pre-Archaeopteryx troodontid theropod from China with long feathers on the metatarsus |journal=Nature
|volume=461 |issue=7264 |year=2009 |pages=640–643 |pmid=19794491 |doi=10.1038/nature08322
|bibcode=2009Natur.461..640H|s2cid=205218015 }}
</ref><ref>
{{Cite journal|author1=Xu, X. |author2=Q. Zhao |author3= M. Norell |author4=C. Sullivan |author5= D. Hone |author6=G. Erickson |author7= X. L. Wang |title=A new feathered maniraptoran dinosaur fossil that fills a morphological gap in avian origin
|journal=Chinese Science Bulletin |volume=54 |year=2009 |pages=430–435 |doi=10.1007/s11434-009-0009-6|issue=3|bibcode=2009SciBu..54..430X |display-authors=etal|doi-access=free }}
</ref>
resolved this paradox. By predating ''Archaeopteryx'', ''Anchiornis'' proves the existence of a modernly feathered theropod ancestor, providing insight into the dinosaur-bird transition. The specimen shows distribution of large pennaceous feathers on the forelimbs and tail, implying that pennaceous feathers spread to the rest of the body at an earlier stage in theropod evolution.<ref>
{{Cite journal|author=Witmer, L. M. |title=Feathered dinosaurs in a tangle |journal=Nature |volume=461 |issue=7264
|year=2009 |pages=601–602 |pmid=19794481 |doi=10.1038/461601a|bibcode = 2009Natur.461..601W |s2cid=205049989 |doi-access=free }}
</ref> The development of pennaceous feathers did not replace earlier filamentous feathers. Filamentous feathers are preserved alongside modern-looking flight feathers – including some with modifications found in the feathers of extant diving birds – in 80 million year old amber from Alberta.<ref>
{{cite news | url=https://www.cbc.ca/news/science/dinosaur-feathers-found-in-alberta-amber-1.1086765 | work=CBC News | title=Dinosaur feathers found in Alberta amber | date=15 September 2011 | url-status=live | archive-url=https://web.archive.org/web/20110915200138/http://www.cbc.ca/news/canada/edmonton/story/2011/09/15/science-dinosaur-feathers.html | archive-date=15 September 2011 }}
</ref>

Two small wings trapped in amber dating to 100 mya show [[plumage]] existed in some bird predecessors. The wings most probably belonged to [[enantiornithes]], a diverse group of avian dinosaurs.<ref>{{Cite web|url=http://news.nationalgeographic.com/2016/06/dinosaur-bird-feather-burma-amber-myanmar-flying-paleontology-enantiornithes|title=Rare Dinosaur-Era Bird Wings Found Trapped in Amber|date=2016-06-28|access-date=2016-06-28|url-status=dead|archive-url=https://web.archive.org/web/20160628165734/http://news.nationalgeographic.com/2016/06/dinosaur-bird-feather-burma-amber-myanmar-flying-paleontology-enantiornithes/|archive-date=28 June 2016}}</ref><ref>{{Cite journal|last1=Xing|first1=Lida|last2=McKellar|first2=Ryan C.|last3=Wang|first3=Min|last4=Bai|first4=Ming|last5=O'Connor|first5=Jingmai K.|last6=Benton|first6=Michael J.|last7=Zhang|first7=Jianping|last8=Wang|first8=Yan|last9=Tseng|first9=Kuowei|date=2016-06-28|title=Mummified precocial bird wings in mid-Cretaceous Burmese amber|journal=Nature Communications|language=en|volume=7|page=12089|doi=10.1038/ncomms12089|pmid=27352215|pmc=4931330|bibcode=2016NatCo...712089X}}</ref>

A large [[Phylogenetics|phylogenetic]] analysis of early dinosaurs by Matthew Baron, [[David B. Norman]] and Paul Barrett (2017) found that [[Theropoda]] is actually more closely related to [[Ornithischia]], to which it formed the [[sister group]] within the [[clade]] [[Ornithoscelida]]. The study also suggested that if the feather-like structures of theropods and ornithischians are of common evolutionary origin then it would be possible that feathers were restricted to Ornithoscelida. If so, then the origin of feathers would have likely occurred as early as the [[Middle Triassic]],<ref name="Ornithoscelida">{{cite journal | last1 = Baron | first1 = M.G. | last2 = Norman | first2 = D.B. | last3 = Barrett | first3 = P.M. | year = 2017 | title = A new hypothesis of dinosaur relationships and early dinosaur evolution | journal = Nature | volume = 543 | issue = 7646| pages = 501–506 | doi = 10.1038/nature21700 | pmid = 28332513 | bibcode = 2017Natur.543..501B | s2cid = 205254710 }}</ref> though this has been disagreed upon.<ref>{{Cite journal |last1=Yang |first1=Zixiao |last2=Jiang |first2=Baoyu |last3=McNamara |first3=Maria E. |last4=Kearns |first4=Stuart L. |last5=Pittman |first5=Michael |last6=Kaye |first6=Thomas G. |last7=Orr |first7=Patrick J. |last8=Xu |first8=Xing |last9=Benton |first9=Michael J. |date=December 17, 2018 |title=Pterosaur integumentary structures with complex feather-like branching |url=https://cora.ucc.ie/bitstream/handle/10468/8311/8816_Yang_et_al_2019_NEE_Pterosaur_feathers.pdf?sequence=1&isAllowed=y |journal=Nature Ecology & Evolution |language=en |volume=3 |issue=1 |pages=24–30 |doi=10.1038/s41559-018-0728-7 |pmid=30568282 |bibcode=2018NatEE...3...24Y |hdl=1983/1f7893a1-924d-4cb3-a4bf-c4b1592356e9 |s2cid=56480710 |issn=2397-334X}}</ref><ref>{{Cite journal |last1=Langer |first1=Max C. |last2=Ezcurra |first2=Martín D. |last3=Rauhut |first3=Oliver W. M. |last4=Benton |first4=Michael J. |last5=Knoll |first5=Fabien |last6=McPhee |first6=Blair W. |last7=Novas |first7=Fernando E. |last8=Pol |first8=Diego |last9=Brusatte |first9=Stephen L. |date=November 2, 2017 |title=Untangling the dinosaur family tree |url=https://research-information.bris.ac.uk/ws/files/136903911/Langer_et_al._reply_to_Baron_et_al._mjb.pdf |journal=Nature |language=en |volume=551 |issue=7678 |pages=E1–E3 |doi=10.1038/nature24011 |pmid=29094688 |bibcode=2017Natur.551E...1L |hdl=1983/d088dae2-c7fa-4d41-9fa2-aeebbfcd2fa3 |s2cid=205260354 |issn=1476-4687}}</ref> The lack of feathers present in large sauropods and ankylosaurs could be that feathers were suppressed by genomic regulators.<ref>{{Cite journal |last1=Benton |first1=Michael J. |last2=Dhouailly |first2=Danielle |last3=Jiang |first3=Baoyu |last4=McNamara |first4=Maria |date=2019-09-01 |title=The Early Origin of Feathers |url=https://cora.ucc.ie/bitstream/handle/10468/8068/10285.pdf?sequence=1 |journal=Trends in Ecology & Evolution |language=en |volume=34 |issue=9 |pages=856–869 |doi=10.1016/j.tree.2019.04.018 |pmid=31164250 |bibcode=2019TEcoE..34..856B |hdl=10468/8068 |s2cid=174811556 |issn=0169-5347}}</ref>

===Evolutionary stages===
[[File:Feather stages diagram.svg|thumb|right|Diagram illustrating stages of evolution]]
Several studies of feather development in the embryos of modern birds, coupled with the distribution of feather types among various prehistoric bird precursors, have allowed scientists to attempt a reconstruction of the sequence in which feathers first evolved and developed into the types found on modern birds.

Feather evolution was broken down into the following stages by Xu and Guo in 2009:<ref name="xu&guo2009">{{cite journal | last1 = Xu | first1 = X. | last2 = Guo | first2 = Y. | year = 2009 | title = The origin and early evolution of feathers: insights from recent paleontological and neontological data |journal = Vertebrata PalAsiatica | volume = 47 | issue = 4| pages = 311–329 }}</ref>
# Single filament
# Multiple filaments joined at their base
# Multiple filaments joined at their base to a central filament
# Multiple filaments along the length of a central filament
# Multiple filaments arising from the edge of a membranous structure
# Pennaceous feather with vane of barbs and barbules and central rachis
# Pennaceous feather with an asymmetrical rachis
# Undifferentiated vane with central rachis

However, Foth (2011) showed that some of these purported stages (stages 2 and 5 in particular) are likely simply artifacts of preservation caused by the way fossil feathers are crushed and the feather remains or imprints are preserved. Foth re-interpreted stage 2 feathers as crushed or misidentified feathers of at least stage 3, and stage 5 feathers as crushed stage 6 feathers.<ref name="foth2011">{{cite journal | last1 = Foth | first1 = C | year = 2011 | title = On the identification of feather structures in stem-line representatives of birds: evidence from fossils and actuopalaeontology | journal = Paläontologische Zeitschrift | volume =  86| pages =  91–102| doi = 10.1007/s12542-011-0111-3 | s2cid = 86362907 }}</ref>

The following simplified diagram of dinosaur relationships follows these results, and shows the likely distribution of plumaceous (downy) and pennaceous (vaned) feathers among dinosaurs and prehistoric birds. The diagram follows one presented by Xu and Guo (2009)<ref name="xu&guo2009"/> modified with the findings of Foth (2011).<ref name="foth2011"/> The numbers accompanying each name refer to the presence of specific feather stages. Note that 's' indicates the known presence of scales on the body.
<div class="noprint">{{clade| style=font-size:80%;line-height:70%
|label1=[[Dinosauria]]
|1={{clade
   |label1=[[Ornithischia]]
   |1={{clade
         |1=[[Heterodontosauridae]] (1)
         |2={{clade
            |1=[[Thyreophora]] (s)
            |2={{clade
               |1=[[Kulindadromeus]] (s, 1, 3)<ref name="Godefroit2014">{{cite journal | last1 = Godefroit | first1 = P. | last2 = Sinitsa | first2 = S.M. | last3 = Dhouailly | first3 = D. | last4 = Bolotsky | first4 = Y.L. | last5 = Sizov | first5 = A.V. | last6 = McNamara | first6 = M.E. | last7 = Benton | first7 = M.J. | last8 = Spagna | first8 = P. | year = 2014 | title = A Jurassic ornithischian dinosaur from Siberia with both feathers and scales | url = http://palaeo.gly.bris.ac.uk/Benton/reprints/2014Kulinda.pdf | journal = Science | volume = 345 | issue = 6195 | pages = 451–455 | doi = 10.1126/science.1253351 | pmid = 25061209 | bibcode = 2014Sci...345..451G | s2cid = 206556907 | access-date = 2016-07-27 | archive-url = https://web.archive.org/web/20190209232112/http://palaeo.gly.bris.ac.uk/Benton/reprints/2014Kulinda.pdf | archive-date = 2019-02-09 | url-status = dead | hdl = 1983/a7ae6dfb-55bf-4ca4-bd8b-a5ea5f323103 | hdl-access = free }}</ref>
               |2={{clade
                  |1=[[Ornithopoda]] (s)
                  |2={{clade
                     |1=[[Psittacosauridae]] (s, 1)
                     |2=[[Ceratopsidae]] (s)
                  }}
               }}
            }}
         }}
      }}
   |label2=[[Saurischia]]
   |2={{clade
      |1=[[Sauropodomorpha]] (s)
      |2={{clade
            |1={{clade
               |1=''[[Aucasaurus]]'' (s)
               |2=''[[Carnotaurus]]'' (s)
               |3=''[[Ceratosaurus]]'' (s)
               }}
            |label2=[[Coelurosauria]]
            |2={{clade
                 |1={{clade
                          |1=''[[Dilong (dinosaur)|Dilong]]'' (3?)
                          |2=Other [[Tyrannosauroidea|tyrannosauroids]] (s, 1)
                     }}
                 |2={{clade
                    |1={{clade
                       |1=''[[Juravenator]]'' (s, 3?)
                       |2=''[[Sinosauropteryx]]'' (3+)
                       }}
                     |label2=[[Maniraptora]]
                     |2={{clade
                           |1=[[Therizinosaur]]ia (1, 3+)
                           |2={{clade
                              |1=[[Alvarezsauridae]] (3?)
                              |2={{clade
                                 |1=[[Oviraptorosauria]] (4, 6)
                                 |label2=[[Paraves]]
                                 |2={{clade
                                 |1={{clade
                                    |1=[[Troodontidae]] (3+, 6)
                                        |2={{clade
                                           |1=Other dromaeosaurids
                                           |2={{clade
                                                 |1=''[[Sinornithosaurus]]'' (3+, 6)
                                                 |2=''[[Microraptor]]'' (3+, 6, 7)
                                              }}
                                           }}
                                        }}
                                       |2={{clade
                                          |1=[[Scansoriopterygidae]] (3+, 6, 8)
                                          |2={{clade
                                             |1=[[Archaeopterygidae]] (3+, 6, 7)
                                             |2={{clade
                                                |1=''[[Jeholornis]]'' (6, 7)
                                                |2={{clade
                                                      |1=''[[Confuciusornis]]'' (4, 6, 7, 8)
                                                      |2={{clade
                                                         |1=[[Enantiornithes]] (4, 6, 7, 8)
                                                         |2=[[Neornithes]] (4, 6, 7, 8)
                        }}
                     }}
                  }}
               }}
            }}
         }}
      }}
   }}
}}
}}
}}
}}
}}
}}
}}
</div>

=== In pterosaurs ===

[[Pterosaur]]s were long known to have filamentous fur-like structures covering their body known as [[pycnofibres]], which were generally considered distinct from the "true feathers" of birds and their dinosaur kin. However, a 2018 study of two small, well-preserved pterosaur fossils from the [[Jurassic]] of [[Inner Mongolia]], [[China]] indicated that pterosaurs were covered in an array of differently-structured pycnofibres (rather than just filamentous ones), with several of these structures displaying diagnostic features of feathers, such as non-veined grouped filaments and bilaterally branched filaments, both of which were originally thought to be exclusive to birds and other maniraptoran dinosaurs. Given these findings, it is possible that feathers have deep evolutionary origins in ancestral [[archosaur]]s, though there is also a possibility that these structures independently evolved to resemble bird feathers via [[convergent evolution]].<ref>{{Cite journal|last1=Unwin|first1=David M.|last2=Martill|first2=David M.|date=December 2020|title=No protofeathers on pterosaurs|url=https://www.nature.com/articles/s41559-020-01308-9|journal=Nature Ecology & Evolution|language=en|volume=4|issue=12|pages=1590–1591|doi=10.1038/s41559-020-01308-9|pmid=32989266|bibcode=2020NatEE...4.1590U |s2cid=222168569|issn=2397-334X|url-access=subscription}}</ref> Mike Benton, the study's senior author, lent credence to the former theory, stating "We couldn't find any anatomical evidence that the four pycnofiber types are in any way different from the feathers of birds and dinosaurs. Therefore, because they are the same, they must share an evolutionary origin, and that was about 250 million years ago, long before the origin of birds."<ref>{{Cite journal|last1=Yang|first1=Zixiao|last2=Jiang|first2=Baoyu|last3=McNamara|first3=Maria E.|last4=Kearns|first4=Stuart L.|last5=Pittman|first5=Michael|last6=Kaye|first6=Thomas G.|last7=Orr|first7=Patrick J.|last8=Xu|first8=Xing|last9=Benton|first9=Michael J.|date=January 2019|title=Pterosaur integumentary structures with complex feather-like branching|journal=Nature Ecology & Evolution|language=en|volume=3|issue=1|pages=24–30|doi=10.1038/s41559-018-0728-7|pmid=30568282|bibcode=2018NatEE...3...24Y |issn=2397-334X|hdl=1983/1f7893a1-924d-4cb3-a4bf-c4b1592356e9|s2cid=56480710|url=https://research-information.bris.ac.uk/ws/files/184677374/Main_Text_revised_mjb.pdf|hdl-access=free}}</ref><ref>{{Cite web|url=http://www.sci-news.com/paleontology/pterosaur-feathers-06733.html|title=Pterosaurs Had Four Types of Feathers, New Study Shows {{!}} Paleontology {{!}} Sci-News.com|website=Breaking Science News {{!}} Sci-News.com|date=18 December 2018 |language=en-US|access-date=2018-12-19}}</ref><ref name="NYT-20181217">{{cite news |last=St. Fleur |first=Nicholas |title=Feathers and Fur Fly Over Pterosaur Fossil Finding – An analysis of two fossils would push back the origins of feathers by about 70 million years, but more specimens may be needed for confirmation. |url=https://www.nytimes.com/2018/12/17/science/pterosaur-feathers-fur.html |date=17 December 2018 |work=[[The New York Times]] |access-date=19 December 2018 }}</ref><ref>{{Cite news|url=https://www.bbc.com/news/science-environment-46572782|title=Fur flies over new pterosaur fossils|last=Briggs|first=Helen|date=2018-12-17|work=BBC News|access-date=2018-12-19|language=en-GB}}</ref> But the integumentary structures of the [[anurognathid]] specimens is still based gross morphology as Liliana D'Alba pointed out. The pycnofibres of the two anurognathid specimens might not be homologous with the filamentous appendages on dinosaurs.<ref>{{Cite journal|last=D'Alba|first=Liliana|date=2019|title=Pterosaur plumage|journal=Nature Ecology & Evolution|language=en|volume=3|issue=1|pages=12–13|doi=10.1038/s41559-018-0767-0|pmid=30568284|s2cid=56480834|issn=2397-334X|doi-access=free}}</ref> Paul M. Barrett suspects that during the integumentary evolution of pterosaurs, pterosaurs primitively lost scales and pycnofibers started to appear.<ref name="youtube.com"/> 

''Cascocauda'' was almost entirely covered in an extensive coat of pycnofibres, which appear to have come in two types. The first are simple, curved filaments that range in length from 3.5–12.8 mm long. These filaments cover most of the animal, including the head, neck, body, limbs and tail. The second type consists of tufts of filaments joined near the base, similar to the branching [[down feathers]] of birds and other [[coelurosaurian]] dinosaurs, around 2.5–8.0 mm long and only cover the wing membranes. Studies of sampled pycnofibres revealed the presence of microbodies within the filaments, resembling the [[melanosome]] pigments identified in other fossil integuments, specifically phaeomelanosomes. Furthermore, [[Infrared spectroscopy|infrared spectral analysis]] of these pycnofibres show similar [[absorption spectra]] to red [[human hair]]. These pycnofibres likely provided both insulation and may have helped streamline the body and wings during flight.<ref name="pycnos">{{Cite journal|author1=Zixiao Yang |author2=Baoyu Jiang |author3=Maria E. McNamara |author4=Stuart L. Kearns |author5=Michael Pittman |author6=Thomas G. Kaye |author7=Patrick J. Orr |author8=Xing Xu |author9=Michael J. Benton |year=2019 |title=Pterosaur integumentary structures with complex feather-like branching |journal=Nature Ecology & Evolution |volume=3 |issue=1 |pages=24–30 |doi=10.1038/s41559-018-0728-7 |pmid=30568282 |bibcode=2018NatEE...3...24Y |hdl=1983/1f7893a1-924d-4cb3-a4bf-c4b1592356e9 |s2cid=56480710 |url=https://research-information.bris.ac.uk/en/publications/1f7893a1-924d-4cb3-a4bf-c4b1592356e9 |hdl-access=free }}</ref>
The identity of these branching structures as pycnofibres or feathers was challenged by Unwin & Martill (2020), who interpreted them as bunched-up and degraded aktinofibrils–stiffening fibres found in the wing membrane of pterosaurs–and attributed the melanosomes and keratin to skin rather than filaments.<ref>{{Cite journal |last1=Unwin |first1=D. M. |last2=Martill |first2=D. M. |year=2020 |title=No protofeathers on pterosaurs |journal=Nature Ecology & Evolution |volume=4 |issue= 12|pages= 1590–1591|doi=10.1038/s41559-020-01308-9 |pmid=32989266 |bibcode=2020NatEE...4.1590U |s2cid=222168569}}</ref> These claims were refuted by Yang and colleagues, who argue that Unwin and Martill's interpretations are inconsistent with the specimen's preservation. Namely, they argue that the consistent structure, regular spacing, and extension of the filaments beyond the wing membrane support their identification as pycnofibres. Further, they argue that the restriction of melanosomes and keratin to the fibres, as occurs in fossil dinosaur feathers, supports the case they are filaments and is not consistent with contamination from preserved skin.<ref>{{Cite journal |last1=Yang |first1=Z. |last2=Jiang |first2=B. |last3=McNamara |first3=M. E. |last4=Kearns |first4=S. L. |last5=Pittman |first5=M. |last6=Kaye |first6=T. G. |last7=Orr |first7=P. J. |last8=Xu |first8=X. |last9=Benton |first9=M. J. |year=2020 |title=Reply to: No protofeathers on pterosaurs |journal=Nature Ecology & Evolution |volume=4 |issue=12 |pages=1592–1593 |doi=10.1038/s41559-020-01309-8 |pmid=32989267 |bibcode=2020NatEE...4.1592Y |s2cid=222163211|hdl=10468/11874 |hdl-access=free }}</ref> Protofeathers likely evolved in early archosaurs, not long after the P-T extinction event during the time metabolic rates of early archosaurs and synapsids were increasing, postures becoming erect, and sustained activity.<ref name=":0" />

==See also==
{{div col|colwidth=30em}}
* [[Feather development]]
* [[Delayed feathering in chickens]]
* [[Hen feathering in cocks]]
* [[Imping]]
* [[List of poultry feathers]]
* [[Pinioning]]
* [[Plumage]]
* [[White feather]]
{{div col end}}

==References==
{{Reflist}}

==Further reading==
* {{Cite book | last=Hanson | first=Thor | year=2011 | title=Feathers: The Evolution of a Natural Miracle |location=New York | publisher=Basic Books | isbn=978-0-465-02013-3 | title-link=Feathers: The Evolution of a Natural Miracle | ref=none }}
*{{ cite book | last1=Lucas | first1=Alfred M. | last2=Stettenheim | first2=Peter R. | year=1972 | chapter=Structure of feathers | title=Avian Anatomy Integument | volume=Part 1 | location=Washington D.C. | publisher=US Department of Agriculture | pages=235–276 | chapter-url=https://books.google.com/books?id=DYIWAAAAYAAJ&pg=PA235 | ref=none}}

==External links==
{{Commons}}
{{Wiktionary|pluma|calamus}}
* McGraw, K. J. 2005. [http://www.public.asu.edu/~kjmcgraw/pubs/ABK2005.pdf Polly want a pigment? Cracking the chemical code to red coloration in parrots.] Australian Birdkeeper Magazine 18:608–611.
* DeMeo, Antonia M. [http://www.animallaw.info/articles/ar22hstclq771.htm ''Access to Eagles and Eagle Parts: Environmental Protection v. Native American Free Exercise of Religion'' (1995)]
* [https://web.archive.org/web/20070610034613/http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&tpl=%2Fecfrbrowse%2FTitle50%2F50cfr22_main_02.tpl Electronic Code of Federal Regulations (e-CFR), ''Title 50: Wildlife and Fisheries PART 22—EAGLE PERMITS'']
* [http://www.animallaw.info/cases/caus649fsupp269.htm U.S. v. Thirty Eight Golden Eagles (1986)]
* [https://web.archive.org/web/20090206211602/http://www.rdg.ac.uk/biomim/personal/richard/keratin.htm Mechanical structure of feathers]
* [http://www.educatedearth.net/video.php?id=4982 Documentary on the evolution of feathers]
* [https://web.archive.org/web/20090303221358/http://faculty.weber.edu/jcavitt/Lecture4.pdf Lecture notes on the avian integument]
* [https://web.archive.org/web/20130508075330/http://www.lab.fws.gov/featheratlas/ U.S. National Fish and Wildlife Forensics Laboratory's Feather Atlas]
* [http://www.federn.org/index_en.html Federn.org]
* [https://featherbase.info/ Featherbase] an extensive online collection of feathers 

{{Birds}}
{{feather-tracts}}

{{Authority control}}

[[Category:Feathers| ]]
[[Category:Bird products]]