Editing Feather (section)

===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>