HOME

TheInfoList




Feathers are epidermal growths that form a distinctive outer covering, or
plumage Plumage ( "feather") is a layer of feather Feathers are epidermal growths that form a distinctive outer covering, or plumage, on dinosaurs, both avian (bird) and some non-avian (non-bird) and possibly other archosauromorphs. They are co ...
, on
dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 annum, million years ago, although the exact origin and timing of the evolution ...

dinosaur
s, both
avian
avian
(bird) and some non-avian (non-bird) and possibly other
archosauromorphs Archosauromorpha (Greek language, Greek for "ruling lizard forms") is a clade of diapsid reptiles containing all reptiles more closely related to archosaurs (such as crocodilians and dinosaurs, including birds) rather than Lepidosauria, lepidosau ...

archosauromorphs
. They are considered the most complex
integumentary The integumentary system is the set of organs forming the outermost layer of an animal's body. It comprises the skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: p ...
structures found in vertebrates and a premier example of a complex evolutionary novelty. They are among the characteristics that distinguish the extant
birds Birds are a group of warm-blooded vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With ...

birds
from other living groups. 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
protection File:CDCA auto repair notice.jpg, Consumer protection laws often mandate the posting of informative notices, such as this one which appears in all Auto mechanic, automotive repair shops in California. Protection is any measure taken to guard ...
. Plumology (or plumage science) is the name for the science that is associated with the study of feathers. Feathers have a number of utilitarian, cultural, and religious uses. Feathers are both soft and excellent at trapping
heat In thermodynamics Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these ...

heat
; thus, they are sometimes used in high-class
bedding Bedding, also known as bedclothes or bed linen, is the materials laid above the mattress A mattress is a large, usually rectangular pad for supporting a lying A lie is an assertion that is believed to be false, typically used with the pur ...

bedding
, especially
pillow A pillow is a support of the body at rest for comfort, therapy, or decoration. Pillows are used by many species, including humans. Some types of pillows include throw pillows, body pillows, decorative pillows and many more. Pillows that aid sl ...

pillow
s,
blanket A blanket is a piece of soft cloth large enough either to cover or to enfold a great portion of the user's body. It is usually used when a person goes to sleep or is otherwise at rest. It traps radiant bodily heat that otherwise would be los ...

blanket
s, and
mattress A mattress is a large, usually rectangular pad for supporting a lying A lie is an assertion that is believed to be false, typically used with the purpose of deceiving someone. The practice of communicating lies is called lying. A person who ...

mattress
es. They are also used as filling for winter
clothing Clothing (also known as clothes, apparel, and attire) are items worn on the body. Typically, clothing is made of fabrics or textile A textile is a flexible material made by creating an interlocking bundle of yarn Yarn is a long ...

clothing
and outdoor bedding, such as quilted coats and
sleeping bag A sleeping bag is an insulated covering for a person, essentially a lightweight quilt that can be closed with a zipper A zipper, zip, fly, or zip fastener, formerly known as a clasp locker, is a commonly used device for binding the edges o ...
s.
Goose A goose (plural geese) is a bird of any of several waterfowl Anseriformes is an order of bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves , characterised by feathers, toothless beaked ...

Goose
and
eider Eiders () are large seaduck The seaducks (''Mergini'') are a tribe of the duck Duck is the common name for numerous species in the waterfowl family (biology), family Anatidae which also includes swans and goose, geese. Ducks are divided ...

eider
down have great ''loft'', the ability to expand from a compressed, stored state to trap large amounts of compartmentalized, insulating air. Feathers of large birds (most often
geese A goose (plural geese) is a bird of any of several waterfowl Anseriformes is an order of bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves , characterised by feathers, toothless beaked ...

geese
) have been and are used to make
quill A quill is a writing tool A writing implement or writing instrument is an object used to produce writing. Writing consists of different figures, lines, and or forms. Most of these items can be also used for other functions such as painting, dra ...

quill
pens. Historically, the hunting of birds for decorative and ornamental feathers has endangered some species and helped to contribute to the extinction of others. Today, feathers used in fashion and in military headdresses and clothes are obtained as a waste product of poultry farming, including
chicken The chicken (''Gallus gallus domesticus'') is a domestication, domesticated subspecies of the red junglefowl originally from Southeastern Asia. Rooster or cock is a term for an adult male bird, and a younger male may be called a cockerel. A m ...

chicken
s,
geese A goose (plural geese) is a bird of any of several waterfowl Anseriformes is an order of bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves , characterised by feathers, toothless beaked ...

geese
,
turkeys The turkey is a large bird in the genus ''Meleagris'', native to North America. There are two extant turkey species: the wild turkey (''Meleagris gallopavo'') of eastern and central North America and the ocellated turkey (''Meleagris ocellata ...
,
pheasant Pheasants () are birds of several genera within the subfamily (biology), subfamily Phasianinae, of the family (biology), family Phasianidae in the order (biology), order Galliformes. Though they can be found world over in introduced (and captive ...

pheasant
s, and
ostrich ''Struthio'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a ...

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

Feather derives from Old English "fether", which is of 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’. Because of the feathers being an integral part of
quills ''Quills'' is a 2000 period film A historical drama (also period drama, costume drama, and period piece) is a work set in a past time period, usually used in the context of film and television. Historical drama includes historical fiction and ...

quills
, which were early pens used for writing, the word pen itself is derived from the Latin ''penna'', meaning feather. The French word ''plume'' can mean ''feather'', ''quill'', or ''pen''.


Structures and characteristics

Feathers are among the most complex
integumentary The integumentary system is the set of organs forming the outermost layer of an animal's body. It comprises the skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: p ...

integumentary
appendages An appendage (or outgrowth) is an external body part, or natural prolongation, that protrudes from an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are co ...
found in
vertebrates Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as an indiv ...

vertebrates
and are formed in tiny follicles in the
epidermis The epidermis is the outermost of the three layers that comprise the skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate Vertebrates () comprise all species of animal Animals (also calle ...
, or outer skin layer, that produce
keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin Alpha-keratin, or α-keratin, is a type of keratin Keratin () is one of a family of fibrous structural proteins known as Scleroprot ...

keratin
protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a No ...

protein
s. The
β-keratin β-keratin or beta-keratin is a member of a structural protein Proteins are large biomolecules or macromolecules that are comprised of one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of func ...
s in feathers,
beak The beak, bill, and/or rostrum is an external anatomical structure found mostly in birds Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves , characterised by feathers, toothless beaked jaws, the Ovi ...

beak
s and
claw A claw is a curved, pointed appendage found at the end of a toe or finger in most amniote Amniotes (from Greek ἀμνίον ''amnion'', "membrane surrounding the fetus", earlier "bowl in which the blood of sacrificed animals was caught", ...

claw
s – and the claws,
scales Scale or scales may refer to: Mathematics * Scale (descriptive set theory)In the mathematical discipline of descriptive set theory, a scale is a certain kind of object defined on a set (mathematics), set of point (mathematics), points in some Poli ...
and
shells Shell may refer to: Architecture and design * Shell (structure), a thin structure **Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses **Thin-shell structure, **Oil company Science Biology * Seashell ...
of
reptile Reptiles, as most commonly defined, are the animals in the class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or ...

reptile
s – are composed of protein strands
hydrogen-bonded
hydrogen-bonded
into β-pleated sheets, which are then further twisted and
crosslinked In chemistry and biology a cross-link is a bond that links one polymer chain to another. These links may take the form of covalent bonds or ionic bonds and the polymers can be either synthetic polymers or natural polymers (such as proteins). ...
by
disulfide In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they underg ...
bridges into structures even tougher than the α-keratins of mammalian
hair Hair is a protein filament In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Ph ...

hair
,
hornsHorns or The Horns may refer to: * The Horns (Colorado), a summit on Cheyenne Mountain * ''Horns'' (novel), a dark fantasy novel written in 2010 by Joe Hill ** ''Horns'' (film), a 2013 film adaptation of Hill's novel * "The Horns" (song), a 2015 ...
and
hooves Cloven hooves of roe deer (''Capreolus capreolus''), with prominent dewclaws A hoof ( or ), plural hooves ( or ) or hoofs , is the tip of a toe Toes are the digits (fingers) of the foot of a tetrapod. Animal Animals (also called M ...
. The exact
signal In signal processing Signal processing is an electrical engineering subfield that focuses on analysing, modifying, and synthesizing signals such as audio signal processing, sound, image processing, images, and scientific measurements. Sig ...

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.


Classification

There are two basic types of feather: vaned feathers which cover the exterior of the body, and
down feather The down of bird Birds are a group of warm-blooded vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological k ...
s which are underneath the vaned feathers. The
pennaceous feather The pennaceous feather is a type of feather Feathers are epidermal growths that form a distinctive outer covering, or plumage, on dinosaurs, both avian (bird) and some non-avian (non-bird) and possibly other archosauromorphs. They are cons ...
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. Filoplumes are entirely absent in
ratite A ratite () is any of a diverse group of mostly flightless s are a well-known example of flightless birds. Flightless birds are birds that through evolution lost the ability to flight, fly. There are over 60 extant species, including the well ...

ratite
s. In some passerines, filoplumes arise exposed beyond the pennaceous feathers on the neck. The remiges, or
flight feather Flight feathers (''Pennae volatus'') are the long, stiff, asymmetrically shaped, but symmetrically paired pennaceous feather The pennaceous feather is a type of feather Feathers are epidermal growths that form a distinctive outer coveri ...
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 In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanis ...

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 A quill is a writing tool A writing implement or writing instrument is an object used to produce writing. Writing consists of different figures, lines, and or forms. Most of these items can be also used for other functions such as painting, dra ...

quill
) which inserts into a in the
skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod exoskeleton, have differ ...

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). Hatchling birds of some species have a special kind of natal down feathers (neossoptiles) which are pushed out when the normal feathers (teleoptiles) emerge. 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, and the lateral walls of rachis region show structure of crossed fibers.


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. Some species have a
crest Crest or CREST may refer to: Buildings *The Crest (Huntington, New York) The Crest is a historic house on Eatons Neck in Suffolk County, New York. Although on the land mass of Eatons Neck, the house today is within the jurisdiction of the Incor ...
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 Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard The leopard (''Pan ...

camouflage
against
predator Predation is a biological interaction In ecology Ecology (from el, οἶκος, "house" and el, -λογία, label=none, "study of") is the study of the relationships between living organisms, including humans, and their physical en ...

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 Sexual dimorphism is the condition where the sex Sex is either of two divisions, typically male Male (♂) is the sex of an organism that produces the gamete known as sperm. A male gamete can fuse with a larger female gamete, or ovum, in ...
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. The wing feathers of male club-winged manakins ''Machaeropterus deliciosus'' have special structures that are used to produce sounds by
stridulation Stridulation is the act of producing sound by rubbing together certain body parts. This behavior is mostly associated with insects, but other animals are known to do this as well, such as a number of species of fish, snakes and spiders. The mech ...
. Some birds have a supply of
powder down alt=Fluffy down feather on white background, Down feather The down of bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves , characterised by feathers, toothless beaked jaws, the Oviparity, lay ...
feathers that grow continuously, with small particles regularly breaking off from the ends of the barbules. These particles produce a
powder A powder is a dry, bulk solid Solid is one of the four fundamental states of matter (the others being liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continually Deformation (mechanic ...
that sifts through the feathers on the bird's body and acts as a waterproofing agent and a feather 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. Waterproofing can be lost by exposure to 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 An oil spill is the release of a liquid petroleum Petroleum, also known as crude oil and oil, is a naturally occurring, yellowish-black liquid A liquid is a nearly incompressible In fluid mechanics or more generally continuum ...
s. The feathers of cormorants soak up water and help to reduce buoyancy, thereby allowing the birds to swim submerged.
Bristle 270px, The bristles of a sweeping brush A bristle is a stiff hair Hair is a protein filament In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry ...
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 An eyelash (also called lash) (Latin: ''Cilia'') is one of the hairs that grows at the edge of the eyelids. It grows in one layer on the edge of the upper and lower eyelids. Eyelashes protect the eye from debris, dust and small particles and pe ...
es and
vibrissae Whiskers, more generally called vibrissae (; singular: vibrissa; ), are a type of stiff, functional hair Hair is a protein filament In biology Biology is the natural science that studies life and living organisms, including th ...
in
mammal Mammals (from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" or "to be i ...
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. In one study, willow flycatchers ('''') were found to catch insects equally well before and after removal of the rictal bristles.
Grebe Grebes () are aquatic diving birds in the order (biology), order Podicipediformes . Grebes are widely distributed birds of freshwater, with some species also occurring in sea, marine habitats during Bird migration, migration and winter. The order ...

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.


Distribution

Contour feathers are not uniformly distributed on the skin of the bird except in some groups such as the
penguin Penguins (order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, dirt, trash, or waste, and t ...

penguin
s, ratites and screamers. 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. Species that incubate their own eggs often lose their feathers on a region of their belly, forming a
brooding patch A brood patch is a patch of featherless skin on the underside of birds during the nesting season. Feathers act as inherent insulators, and prevent efficient incubation. Birds have solved this evolutionary dilemma by developing dedicated brood patche ...
.


Coloration

The colors of feathers are produced by pigments, by microscopic structures that can
refract In physics, refraction is the change in direction of a wave In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that ...

refract
, reflect, or scatter selected wavelengths of light, or by a combination of both. Most feather pigments are
melanin Melanin (; from el, μέλας ''melas'', "black, dark") is a broad term for a group of natural pigments found in most organisms. Melanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the ami ...

melanin
s (brown and beige
pheomelanin Melanin (; from el, μέλας ''melas'', "black, dark") is a broad term for a group of natural pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at ...
s, black and grey
eumelanin Melanin (; from el, μέλας ''melas'', "black, dark") is a broad term for a group of natural pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at ...
s) and
carotenoid Carotenoids (), also called tetraterpenoids, are yellow, orange, and red organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ (anatomy), organ Chemistry * Organ ...
s (red, yellow, orange); other pigments occur only in certain
taxa In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechani ...
– the yellow to red psittacofulvins (found in some
parrot Parrots, also known as psittacines , are birds of the roughly 398 species in 92 genus (biology), genera comprising the order (biology), order Psittaciformes , found mostly in tropics, tropical and subtropics, subtropical regions. The order is s ...

parrot
s) and the red
turacin Turacin is a naturally occurring red pigment that is 6% copper complexed to uroporphyrin III. Arthur Herbert Church discovered turacin in 1869. It is found only in the bird family (biology), family Musophagidae, the turacos. Other birds derive the ...

turacin
and green
turacoverdin Turacoverdin is a unique copper porphyrin, uroporphyrin pigment responsible for the bright green coloration of several birds of the family Turaco, Musophagidae, most notably the turaco. It is chemically related to turacin, a red pigment also found ...
(
porphyrin Porphyrins ( ) are a group of heterocyclic 125px, Pyridine, a heterocyclic compound A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different chemical element, elements as members of its ring(s). ...

porphyrin
pigments found only in
turaco The turacos make up the bird Birds are a group of warm-blooded vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), ...
s).
Structural coloration In living creatures, structural coloration is the production of colour by microscopically structured surfaces fine enough to interfere with visible light, sometimes in combination with pigments. For example, peacock tail feathers are pigmented ...
is involved in the production of blue colors,
iridescence Iridescence (also known as goniochromism) is the phenomenon of certain surfaces that appear to gradually change color Color (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States Englis ...
, most
ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, ...

ultraviolet
reflectance and in the enhancement of pigmentary colors. Structural iridescence has been reported 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 The budgerigar (; ''Melopsittacus undulatus'') is a small, long-tailed, seed-eating parrot Parrots, also known as psittacines , are bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves , ch ...
s). The blues and bright greens of many
parrot Parrots, also known as psittacines , are birds of the roughly 398 species in 92 genus (biology), genera comprising the order (biology), order Psittaciformes , found mostly in tropics, tropical and subtropics, subtropical regions. The order is s ...

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, the specific feather structure involved is called by some the Dyck texture. Melanin is often involved in the absorption of light; in combination with a yellow pigment, it produces a dull olive-green. In some birds, feather colors may be created, or altered, by secretions from the
uropygial gland The uropygial gland, informally known as the preen gland or the oil gland, is a bilobed sebaceous gland A sebaceous gland is a microscopic exocrine gland A gland is a group of cells in an animal's body that synthesizes substances (such as hor ...
, 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, but studies have failed to find evidence. The oil secretion from the uropygial gland may also have an inhibitory effect on feather bacteria. 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, and/or because carotenoids are required for immune function and hence sexual displays come at the expense of health. A bird's feathers undergo wear and tear and are replaced periodically during the bird's life through
molt In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer ...
ing. New feathers, known when developing as 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. 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. 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 ruleGloger's rule is an ecogeographical rule which states that within a species of endotherms, more heavily pigmented forms tend to be found in more humid environments, e.g. near the equator The Earth's equator is an imaginary planetary line t ...
. 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. 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. 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.


Parasites

The feather surface is the home for some ectoparasites, notably feather lice (
Phthiraptera Louse (plural: lice) is the common name for members of the order (biology), order Phthiraptera, which contains nearly 5,000 species of wingless insect. Lice are obligate parasites, living externally on warm-blooded Host (biology), hosts which ...
) 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 hitching a ride on a fly. File:Phoresy_edited.png, A pseudoscorpion on the leg of a crane fly Phoresis or phoresy is a non-permanent, Commensalism, commensalistic interaction in which one organism (a phoront or phoretic) attaches itself to anoth ...

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. Feather holes are chewing traces of lice (most probably '' Brueelia'' spp. lice) on the wing and tail feathers. They were described on
barn swallow The barn swallow (''Hirundo rustica'') is the most widespread species of swallow The swallows, martins, and saw-wings, or Hirundinidae, are a family of passerine A passerine is any bird of the Order (biology), order Passeriformes (, Lat ...

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. Birds maintain their feather condition by and bathing in water or
dust Dust is made of s of solid . On Earth, it generally consists of particles in the that come from various sources such as lifted by wind (an ), , and . Dust in homes is composed of about 20–50% dead . The rest, and in offices, and other ...
. It has been suggested that a peculiar behavior of birds,
anting Anting () is a town in Jiading District, Shanghai, bordering Kunshan, Jiangsu to the west. It has 96,000 inhabitants and, after the July 2009 merger of Huangdu (), an area of .
, in which ants are introduced into the plumage, helps to reduce parasites, but no supporting evidence has been found.


Human usage


Utilitarian

Bird feathers have long been used for
fletching Fletching is the fin A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foils that produce lift or thrust Thrust is a reaction (physics), reaction force (physics), force described ...
arrowsArrows may refer to: * more than one arrow * Arrows (Australian band), indie rock band established 2006 * Arrows (British band), 1970s Anglo-American glam rock-pop band * Arrows (Unicode block), a Unicode block containing line, curve, and semicircle ...
. Colorful feathers such as those belonging to
pheasant Pheasants () are birds of several genera within the subfamily (biology), subfamily Phasianinae, of the family (biology), family Phasianidae in the order (biology), order Galliformes. Though they can be found world over in introduced (and captive ...

pheasant
s have been used to decorate
fishing lure A fishing lure is a type of artificial fishing bait which is designed to attract the attention of predatory fish, using prey-like appearances, movements, vibrations, specular reflection, bright reflections and flashy colors to appeal to the fish ...

fishing lure
s. Feathers are also valuable in aiding the identification of species in forensic studies, particularly in
bird strike A bird strike—sometimes called birdstrike, bird ingestion (for an engine), bird hit, or bird aircraft strike hazard (BASH)—is a collision between an airborne animal (usually a or ) and a moving vehicle, usually an . The term is also used fo ...
s to aircraft. The ratios of hydrogen isotopes in feathers help in determining the geographic origins of birds. Feathers may also be useful in the non-destructive sampling of pollutants. 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, biodegradeable polymers, and production of enzymes. Feather proteins have been tried as an adhesive for wood board. 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.


In religion and culture

Eagle Eagle is the common name for many large birds of prey Birds of prey, also known as raptors, include species of bird Birds are a group of s constituting the Aves , characterised by s, toothless beaked jaws, the of eggs, a high ...

Eagle
feathers have great cultural and spiritual value to American Indians in the US and
First Nations The First Nations (french: Premières Nations ) are groups of Canadian indigenous peoples, who are classified as distinct from the Inuit Inuit (; iu, ᐃᓄᐃᑦ 'the people', singular: Inuk, , dual: Inuuk, ) are a group of culturally s ...
peoples in
Canada Canada is a country in the northern part of North America North America is a continent A continent is any of several large landmasses. Generally identified by convention (norm), convention rather than any strict criteria, ...

Canada
as religious objects. In the United States, the religious use of eagle and
hawk Hawks are a group of medium- diurnal birds of prey Birds of prey, also known as raptors, include species of bird that primarily hunt and feed on vertebrates that are large relative to the hunter. Additionally, they have Bird vision, keen ey ...

hawk
feathers is governed by the
eagle feather law In the United States The United States of America (USA), commonly known as the United States (U.S. or US), or America, is a country Contiguous United States, primarily located in North America. It consists of 50 U.S. state, states, a Was ...
, 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 Condor is the common name for two species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the larges ...

condor
s are used in traditional medications. In India, feathers of the
Indian peacock The Indian peafowl (''Pavo cristatus''), also known as the common peafowl, and blue peafowl, is a peafowl species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, ...

Indian peacock
have been used in traditional medicine for snakebite, infertility, and coughs. Members of Scotland's
Clan Campbell Clan Campbell ( gd, Na Caimbeulaich ) is a Scottish Highlands, Highland Scottish clan. Historically one of the largest and most powerful of the Highland clans, their lands were in Argyll and the chief of the clan became the Earl and later Duke of ...

Clan Campbell
are known to wear feathers on their bonnets to signify authority within the clan. Clan chiefs wear three, chieftains wear two and an
armiger In heraldry Heraldry () is a discipline relating to the design, display and study of armorial bearings (known as armory), as well as related disciplines, such as vexillology Vexillology () is the study of the history, symbolism and usage ...
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. 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 Victorian fashion consists of the various fashions and trends in British culture British culture is influenced by the combined nations' history; its historically Christian religious life A religious institute is a type of institute ...
). 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. For instance, South American
hummingbird Hummingbirds are Bird, birds native to the Americas and comprise the Family (biology), biological family Trochilidae. With about 360 species, they occur from Alaska to Tierra del Fuego, but the vast majority of the species are found in the tropi ...

hummingbird
feathers were used in the past to dress some of the miniature birds featured in
singing bird box A singing bird box (''boîte à oiseau chanteur'' in French) is a box, usually rectangular-shaped, which contains within a miniature automaton automaton. An automaton (; plural: automata or automatons) is a relatively self-operating machin ...
es. This trade caused severe losses to bird populations (for example,
egret Egrets are herons that have white or buff plumage, developing fine plumes (usually milky white) during the breeding season. Egrets are not a biologically distinct group from herons and have the same build. Biology Many egrets are members of ...

egret
s and
whooping crane Named for its whooping sound, the whooping crane (''Grus americana'') is the tallest North America North America is a continent A continent is any of several large landmasses. Generally identified by convention (norm), conventi ...

whooping crane
s). Conservationists led a major campaign against the use of feathers in hats. This contributed to passage of the
Lacey Act The Lacey Act of 1900, or simply the Lacey Act () is a Conservation movement, conservation law in the United States that prohibits trade in wildlife, fish, and plants that have been illegally taken, possessed, transported, or sold. Introduced into ...
in 1900, and to changes in fashion. The ornamental feather market then largely collapsed. More recently, rooster plumage has become a popular trend as a
hairstyle A hairstyle, hairdo, haircut or coiffure refers to the fashion, styling of hair, usually on the human scalp. Sometimes, this could also mean an editing of facial or body hair. The fashioning of hair can be considered an aspect of personal ...

hairstyle
accessory, with feathers formerly used as fishing lures now being used to provide color and style to hair. 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

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, 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. 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. Recent discoveries are argued to support a thermoregulatory function, at least in smaller dinosaurs. Some researchers even argue that thermoregulation arose from bristles on the face that were used as tactile sensors. While feathers have been suggested as having evolved from reptilian
scales Scale or scales may refer to: Mathematics * Scale (descriptive set theory)In the mathematical discipline of descriptive set theory, a scale is a certain kind of object defined on a set (mathematics), set of point (mathematics), points in some Poli ...
, there are numerous objections to that idea, and more recent explanations have arisen from the paradigm of
evolutionary developmental biology Evolutionary developmental biology (informally, evo-devo) is a field of biological research Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processe ...
. 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. 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. The miniaturization of birds also played a role in the evolution of powered flight. The coloration of feathers is believed to have evolved primarily in response to
sexual selection Sexual selection is a mode of natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype right , Here the relation between genotype and phenotype is illustrat ...
. In one fossil specimen of the
paravian Paraves are a widespread group of theropod dinosaurs that originated in the Late Jurassic period. In addition to the extinct dromaeosauridae, dromaeosaurids, troodontidae, troodontids, Anchiornithidae, anchiornithids, and scansoriopterygidae, sca ...
'''', the features are so well preserved that the
melanosome Fish and frog melanophores are cells that can change colour by dispersing or aggregating pigment-containing melanosomes. A melanosome is an organelle In cell biology, an organelle is a specialized subunit, usually within a cell (biology), cell, ...
(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'' could be determined. ''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 Mate choice is one of the primary mechanisms under which evolution can occur. It is characterized by a "selective response by animals to particular stimuli" which can be observed as behavior.Bateson, Paul Patrick Gordon. "Mate Choice." Mate Choic ...
. Additionally, when comparing different '''' 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. Feathers and scales are made up of two distinct forms of
keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin Alpha-keratin, or α-keratin, is a type of keratin Keratin () is one of a family of fibrous structural proteins known as Scleroprot ...

keratin
, and it was long thought that each type of keratin was exclusive to each skin structure (feathers and scales). However, a study published in 2006 confirmed the presence of feather keratin in the early stages of development of
American alligator The American alligator (''Alligator mississippiensis''), sometimes referred to colloquially as a gator or common alligator, is a large crocodilian Crocodilia (or Crocodylia, both ) is an order Order or ORDER or Orders may refer to: * O ...

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 homologous keratin in both birds and
crocodilian Crocodilia (or Crocodylia, both ) is an order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, ...
s indicates that it was inherited from a common ancestor. This may suggest that crocodilian scales, bird and dinosaur feathers, and pterosaur pycnofibres are all developmental expressions of the same primitive archosaur skin structures; suggesting that feathers and pycnofibers could be homologous. But a book published in 2020 named "The Evolution of Feathers: From Their Origin to the Present" has a different conclusion, they don't find it likely that pycnofibers and feathers likely and find it that pterosaur pycnofibers are poor models for constraining the evolutionary origin of feathers.


Feathered dinosaurs

Several non-avian
dinosaurs Dinosaurs are a diverse group of reptile Reptiles, as most commonly defined, are the animals in the class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge ...
had feathers on their limbs that would not have functioned for flight. One theory suggests that feathers originally evolved on dinosaurs due to their 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 ''Archaeopteryx'' ( "old wing"), sometimes referred to by its German name, ' ("original bird" or "first bird"), is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification ...

Archaeopteryx
'' and ''
Microraptor ''Microraptor'' (Greek language, Greek, μικρός, ''mīkros'': "small"; Latin language, Latin, ''raptor'': "one who seizes") is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovere ...

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. Dinosaurs that had feathers or protofeathers include ''
Pedopenna ''Pedopenna'' (meaning "foot feather") is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. Th ...

Pedopenna
daohugouensis'' and ''
Dilong paradoxus ''Dilong'' (帝龍, which means 'emperor dragon') is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classi ...

Dilong paradoxus
'', a
tyrannosauroid Tyrannosauroidea (meaning 'tyrant lizard forms') is a Taxonomic rank, superfamily (or clade) of coelurosaurian theropod dinosaurs that includes the family (biology), family Tyrannosauridae as well as more basal (phylogenetics), basal relatives. ...
which is 60 to 70 million years older than ''
Tyrannosaurus rex ''Tyrannosaurus'' is a genus of large theropoda, theropod dinosaur. The species ''Tyrannosaurus rex'' (''rex'' meaning "king" in Latin), often called ''T. rex'' or colloquially ''T-Rex'', is one of the best represented theropods. ''Tyrannosau ...

Tyrannosaurus rex
'' although ''Dilong'' paradoxus might not be a tyrannosauroid. The majority of dinosaurs known to have had feathers or protofeathers are
theropods Theropoda ( from Greek 'wild beast' and 'foot'), whose members are known as theropods, is a dinosaur Dinosaurs are a diverse group of reptiles of the clade A clade (; from grc, , ''klados'', "branch"), also known as a monophyleti ...

theropods
, however featherlike "filamentous integumentary structures" are also known from the
ornithischian Ornithischia () is an extinct clade of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves , ...
dinosaurs ''
Tianyulong ''Tianyulong'' (Chinese language, Chinese: 天宇龍; Hanyu Pinyin, Pinyin: ''tiānyǔlóng''; named for the Shandong Tianyu Museum of Nature where the holotype fossil is housed) is an extinct genus of heterodontosaurid ornithischian dinosaur. Th ...

Tianyulong
'' and ''
Psittacosaurus ''Psittacosaurus'' ( ; "parrot lizard") is a genus of extinct ceratopsian dinosaur from the Early Cretaceous of what is now Asia, existing between 126 and 101 million years ago. It is notable for being the most species-rich non-avian dinosaur gen ...

Psittacosaurus
''. The exact nature of these structures is still under study. However, it is believed that the stage-1 feathers (see Evolutionary stages section below) such as those seen in these two ornithischians likely functioned in display. In 2014, the ornithischian ''
Kulindadromeus ''Kulindadromeus'' was a herbivorous dinosaur Dinosaurs are a diverse group of reptiles of the clade A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural group, is a group of organisms that are ...
'' was reported as having structures resembling stage-3 feathers. A 2016 paper published had a different conclusion that the tail bristles of ''Psittacosaurus'' and the monofilaments of ''Kulindadromeus'' were actually highly deformed scales since the morphology and anatomy didn't resemble feathers and filaments. Although feather beta keratin is present in crocodilian scales in embryonic development, it doesn't change maximum likelihood reconstructions by Paul M. Barrett and colleagues where they find that scales are plesiomorphic to dinosaurs and find it more likely that filaments first originated in Coelurosauria. In 2010, a new
carcharodontosaurid Carcharodontosaurids (from the Greek language, Greek καρχαροδοντόσαυρος, ''carcharodontósauros'': "shark-toothed lizards") were a group of carnivorous theropod dinosaurs. In 1931 Ernst Stromer named Carcharodontosauridae as a ...
named was found to have
remiges Flight feathers (''Pennae volatus'') are the long, stiff, asymmetrically shaped, but symmetrically paired pennaceous feather The pennaceous feather is a type of feather Feathers are epidermal growths that form a distinctive outer coveri ...
on the ulna suggesting it could have feathers on its arms. However there has been criticisms with the publication where they point out that the bumps on the ulna of ''Concavenator'' are on the anterolateral which is unlike remiges which are in a posterolateral on the ulna of some birds, they consider it more likely that these are attachments for interosseous ligaments. Since the 1990s, dozens of feathered dinosaurs have been discovered in the clade
Maniraptora Maniraptora is a clade A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic—that is, composed of a common ancestor and all its lineage ( ...
, which includes the clade Avialae and the recent common ancestors of birds,
Oviraptorosauria Oviraptorosaurs ("egg thief lizards") are a group of feathered maniraptoran dinosaurs from the Cretaceous Period of what are now Asia Asia () is Earth's largest and most populous continent, located primarily in the Eastern Hemisphere, ...

Oviraptorosauria
and
Deinonychosauria Deinonychosauria is a clade of maniraptora Maniraptora is a clade A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic—that is, compos ...
. In 1998, the discovery of a feathered oviraptorosaurian, ''Caudipteryx zoui'', challenged the notion of feathers as a structure exclusive to Avialae. 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 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 Troodontidae is a family In human society A society is a Social group, group of individuals involved in persistent Social relation, social interaction, or a large social group sharing the same spatial or social territory, typicall ...

Troodontidae
and
Dromaeosauridae Dromaeosauridae is a family In , family (from la, familia) is a of people related either by (by recognized birth) or (by marriage or other relationship). The purpose of families is to maintain the well-being of its members and of so ...
. 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). Previously, a temporal paradox existed in the evolution of feathers—theropods with highly derived bird-like characteristics occurred at a later time than ''
Archaeopteryx ''Archaeopteryx'' ( "old wing"), sometimes referred to by its German name, ' ("original bird" or "first bird"), is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification ...

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 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. 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. Two small wings trapped in amber dating to 100 mya show
plumage Plumage ( "feather") is a layer of feather Feathers are epidermal growths that form a distinctive outer covering, or plumage, on dinosaurs, both avian (bird) and some non-avian (non-bird) and possibly other archosauromorphs. They are co ...
existed in some bird predecessors. The wings most probably belonged to
enantiornithes The Enantiornithes, also known as enantiornithines or enantiornitheans in literature, are a group of extinct Avialae, avialans ("birds" in the broad sense), the most abundant and diverse group known from the Mesozoic era. Almost all retained teeth ...
, a diverse group of avian dinosaurs. A large
phylogenetic In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanism ...

phylogenetic
analysis of early dinosaurs by Matthew Baron, David B. Norman and Paul Barrett (2017) found that
Theropoda Theropoda ( from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is appro ...

Theropoda
is actually more closely related to
Ornithischia Ornithischia () is an extinct Order (biology), order of mainly Herbivore, herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name ''Ornithischia'', or "bird-hipped", reflects this similarity and is ...

Ornithischia
, to which it formed the
sister group In phylogenetics, a sister group or sister taxon comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and taxon B are sister groups to eac ...
within the
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic – that is, composed of a common ancestor and all its lineage (evolution), lineal descendants - on a phylogenetic tree. R ...

clade
Ornithoscelida Ornithoscelida () is a proposed clade A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic—that is, composed of a common ancestor and al ...
. 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 In the geologic timescale The geologic time scale (GTS) is a system of chronological datingChronological dating, or simply dating, is the process of attributing to an object or event a date in the past, allowing such object or event to be locat ...
. But according to an analysis by Ji Qiang and colleagues, this might not be true about the evolution of feathers.


Evolutionary stages

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: # 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. 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) modified with the findings of Foth (2011) and Qiang et al. 2016. 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.


In pterosaurs

Pterosaur Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") were flying reptiles of the extinct clade or Order (biology), order Pterosauria. They existed during most of the Mesozoic: from the late Triassic to the end of the Cretac ...
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 archosaurs, though there is also a possibility that these structures independently evolved to resemble bird feathers via convergent evolution. 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." 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. Paul M. Barrett suspects that during the integumentary evolution of pterosaurs, pterosaurs primitively lost scales and pycnofibers started to appear.


See also

* Feather development * Delayed feathering in chickens * Hen feathering in cocks * Imping * List of poultry feathers * Pinioning * Plumage * White feather


References


Further reading

* *


External links

* McGraw, K. J. 2005
Polly want a pigment? Cracking the chemical code to red coloration in parrots.
Australian Birdkeeper Magazine 18:608–611. * DeMeo, Antonia M

* [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'']
U.S. v. Thirty Eight Golden Eagles (1986)



Documentary on the evolution of feathers

Lecture notes on the avian integument

U.S. National Fish and Wildlife Forensics Laboratory's Feather Atlas


{{Authority control Feathers, Bird products