![Types de plumes](https://upload.wikimedia.org/wikipedia/commons/8/80/Types_de_plumes._-_Larousse_pour_tous%2C_-1907-1910-.jpg)
Feathers are
epidermal
The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water relea ...
growths that form a distinctive outer covering, or
plumage, on both
avian
Avian may refer to:
*Birds or Aves, winged animals
*Avian (given name) (russian: Авиа́н, link=no), a male forename
Aviation
*Avro Avian, a series of light aircraft made by Avro in the 1920s and 1930s
*Avian Limited, a hang glider manufacture ...
(bird) and some non-avian
dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
s and other
archosaurs. They are 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 and its appendages, which act as a physical barrier between the external environment and the internal environment that it serves ...
structures found in vertebrates
and a premier example of a complex evolutionary novelty.
They are among the characteristics that distinguish the extant
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
Protection is any measure taken to guard a thing against damage caused by outside forces. Protection can be provided to physical objects, including organisms, to systems, and to intangible things like civil and political rights. Although th ...
.
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, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is ...
; thus, they are sometimes used in high-class
bedding
Bedding, also known as bedclothes or bed linen, is the materials laid above the mattress of a bed for hygiene, warmth, protection of the mattress, and decorative effect. Bedding is the removable and washable portion of a human sleeping environm ...
, especially
pillow
A pillow is a support of the body at rest for comfort, therapy, or decoration. Pillows are used in different variations by many species, including humans. Some types of pillows include throw pillows, body pillows, decorative pillows, and man ...
s,
blanket
A blanket is a swath of soft cloth large enough either to cover or to enfold most of the user's body and thick enough to keep the body warm by trapping radiant body heat that otherwise would be lost through convection.
Etymology
The term ...
s, and
mattresses. 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 textiles, but over time it has included garments made from animal skin and other thin sheets of materials and natural ...
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 or similar means to form a tube, which functions as lightweight, portable bedding in situations where a person is sleeping ...
s.
Goose
A goose ( : geese) is a bird of any of several waterfowl species in the family Anatidae. This group comprises the genera ''Anser'' (the grey geese and white geese) and '' Branta'' (the black geese). Some other birds, mostly related to the ...
and
eider
Eiders () are large seaducks in the genus ''Somateria''. The three extant species all breed in the cooler latitudes of the Northern Hemisphere.
The down feathers of eider ducks, and some other ducks and geese, are used to fill pillows and quil ...
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 ( : geese) is a bird of any of several waterfowl species in the family Anatidae. This group comprises the genera '' Anser'' (the grey geese and white geese) and ''Branta'' (the black geese). Some other birds, mostly related to the she ...
) have been and are used to make
quill
A quill is a writing tool made from a moulted flight feather (preferably a primary wing-feather) of a large bird. Quills were used for writing with ink before the invention of the dip pen, the metal- nibbed pen, the fountain pen, and, eventual ...
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 domesticated junglefowl species, with attributes of wild species such as the grey and the Ceylon junglefowl that are originally from Southeastern Asia. Rooster or cock is a term for an adu ...
s,
geese
A goose ( : geese) is a bird of any of several waterfowl species in the family Anatidae. This group comprises the genera '' Anser'' (the grey geese and white geese) and ''Branta'' (the black geese). Some other birds, mostly related to the she ...
,
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 ocellat ...
,
pheasant
Pheasants ( ) are birds of several genera within the family Phasianidae in the order Galliformes. Although they can be found all over the world in introduced (and captive) populations, the pheasant genera native range is restricted to Eurasia ...
s, and
ostrich
Ostriches are large flightless birds of the genus ''Struthio'' in the order Struthioniformes, part of the infra-class Palaeognathae, a diverse group of flightless birds also known as ratites that includes the emus, rheas, and kiwis. There ...
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 the
Old English
Old English (, ), or Anglo-Saxon, is the earliest recorded form of the English language, spoken in England and southern and eastern Scotland in the early Middle Ages. It was brought to Great Britain by Anglo-Saxon settlers in the mid-5th c ...
"feþer", 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 feathers being an integral part of
quill
A quill is a writing tool made from a moulted flight feather (preferably a primary wing-feather) of a large bird. Quills were used for writing with ink before the invention of the dip pen, the metal- nibbed pen, the fountain pen, and, eventual ...
s, which were early pens used for writing, the word pen itself is derived from the
Latin
Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
''penna'', meaning feather. The French word ''plume'' can mean ''feather'', ''quill'', or ''pen''.
Structures and characteristics
![Parrot-feather](https://upload.wikimedia.org/wikipedia/commons/e/e7/Parrot-feather.jpg)
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 and its appendages, which act as a physical barrier between the external environment and the internal environment that it serves ...
appendages
An appendage (or outgrowth) is an external body part, or natural prolongation, that protrudes from an organism's body.
In arthropods, an appendage refers to any of the homologous body parts that may extend from a body segment, including anten ...
found in
vertebrates
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () (chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with c ...
and are formed in tiny follicles in the
epidermis, or outer skin layer, that produce
keratin
Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin (α-keratin) is a type of keratin found in vertebrates. It is the key structural material making up scales, hair, nails, feathers, ho ...
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
s. The
β-keratins in feathers,
beak
The beak, bill, or rostrum is an external anatomical structure found mostly in birds, but also in turtles, non-avian dinosaurs and a few mammals. A beak is used for eating, preening, manipulating objects, killing prey, fighting, probing for foo ...
s and
claw
A claw is a curved, pointed appendage found at the end of a toe or finger in most amniotes (mammals, reptiles, birds). Some invertebrates such as beetles and spiders have somewhat similar fine, hooked structures at the end of the leg or tarsus ...
s – and the claws,
scales
Scale or scales may refer to:
Mathematics
* Scale (descriptive set theory), an object defined on a set of points
* Scale (ratio), the ratio of a linear dimension of a model to the corresponding dimension of the original
* Scale factor, a number w ...
and
shells of
reptiles – are composed of protein strands
hydrogen-bonded into
β-pleated sheets, which are then further twisted and
crosslinked
In chemistry and biology a cross-link is a bond or a short sequence of bonds 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 ...
by
disulfide
In biochemistry, a disulfide (or disulphide in British English) refers to a functional group with the structure . The linkage is also called an SS-bond or sometimes a disulfide bridge and is usually derived by the coupling of two thiol groups. In ...
bridges into structures even tougher than the
α-keratins of mammalian
hair,
horns Horns or The Horns may refer to:
* Plural of Horn (instrument), a group of musical instruments all with a horn-shaped bells
* The Horns (Colorado), a summit on Cheyenne Mountain
* ''Horns'' (novel), a dark fantasy novel written in 2010 by Joe Hill ...
and
hooves
The hoof (plural: hooves) is the tip of a toe of an ungulate mammal, which is covered and strengthened with a thick and horny keratin covering. Artiodactyls are even-toed ungulates, species whose feet have an even number of digits, yet the rumi ...
. The exact
signal
In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The '' IEEE Transactions on Signal Processing' ...
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 birds is a layer of fine feathers found under the tougher exterior feathers. Very young birds are clad only in down. Powder down is a specialized type of down found only in a few groups of birds. Down is a fine thermal insulator an ...
s which are underneath the vaned feathers. The
pennaceous feather
The pennaceous feather is a type of feather present in most modern birds and in some other species of maniraptoriform dinosaurs.
Description
A pennaceous feather has a stalk or quill. Its basal part, called a ''calamus'', is embedded in the skin ...
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
ratites. In some passerines, filoplumes arise exposed beyond the pennaceous feathers on the neck.
[ The remiges, or flight feathers 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, a rachis (from the grc, ῥάχις [], "backbone, spine") is a main axis or "shaft".
In zoology and microbiology
In vertebrates, ''rachis'' can refer to the series of articulated vertebrae, which encase the spinal cord. In this c ...
. 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 made from a moulted flight feather (preferably a primary wing-feather) of a large bird. Quills were used for writing with ink before the invention of the dip pen, the metal- nibbed pen, the fountain pen, and, eventual ...
) which inserts into a follicle 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 animal coverings, such as the arthropod exoskeleton, have different de ...
. 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), a historic house in Suffolk County, New York
*"The Crest", an alternate name for 63 Wall Street, in Manhattan, New York
*Crest Castle (Château Du Crest), Jussy, Switzerla ...
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's spotted coat, the b ...
against predator
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...
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 sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most an ...
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 manakin
The club-winged manakin (''Machaeropterus deliciosus'') is a small passerine bird which is a resident breeding species in the cloud forest on the western slopes of the Andes Mountains of Colombia and northwestern Ecuador. The manakins are a famil ...
s ''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
The down of birds is a layer of fine feathers found under the tougher exterior feathers. Very young birds are clad only in down. Powder down is a specialized type of down found only in a few groups of birds. Down is a fine thermal insulator an ...
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 composed of many very fine particles that may flow freely when shaken or tilted. Powders are a special sub-class of granular materials, although the terms ''powder'' and '' granular'' are sometimes used to distin ...
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 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 spills. The feathers of cormorants soak up water and help to reduce buoyancy, thereby allowing the birds to swim submerged.
]
Bristle
A bristle is a stiff hair or feather (natural or artificial), either on an animal, such as a pig, a plant, or on a tool such as a brush or broom.
Synthetic types
Synthetic materials such as nylon are also used to make bristles in items such as ...
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 p ...
es and vibrissae
Vibrissae (; singular: vibrissa; ), more generally called Whiskers, are a type of stiff, functional hair used by mammals to sense their environment. These hairs are finely specialised for this purpose, whereas other types of hair are coarser ...
in mammals. 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 (''Empidonax traillii
The willow flycatcher (''Empidonax traillii'') is a small insect-eating, neotropical migrant bird of the tyrant flycatcher family. There are four subspecies of the willow flycatcher currently recognized, all of which breed in North America (inc ...
'') were found to catch insects equally well before and after removal of the rictal bristles.
Grebe
Grebes () are aquatic diving birds in the order Podicipediformes . Grebes are widely distributed freshwater birds, with some species also found in marine habitats during migration and winter. Some flightless species exist as well, most notably ...
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 penguins, 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 patc ...
.
Coloration
The colors of feathers are produced by pigments, by microscopic structures that can refract
In physics, refraction is the redirection of a wave as it passes from one medium to another. The redirection can be caused by the wave's change in speed or by a change in the medium. Refraction of light is the most commonly observed phenomeno ...
, 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. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amino ...
s (brown and beige pheomelanin
Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the a ...
s, black and grey eumelanins) and carotenoids (red, yellow, orange); other pigments occur only in certain taxa
In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...
– the yellow to red psittacofulvins (found in some parrot
Parrots, also known as psittacines (), are birds of the roughly 398 species in 92 genera comprising the order Psittaciformes (), found mostly in tropical and subtropical regions. The order is subdivided into three superfamilies: the Psittacoide ...
s) and the red turacin and green turacoverdin (porphyrin
Porphyrins ( ) are a group of heterocyclic macrocycle organic compounds, composed of four modified pyrrole subunits interconnected at their α carbon atoms via methine bridges (=CH−). The parent of porphyrin is porphine, a rare chemical com ...
pigments found only in turaco
The turacos make up the bird family Musophagidae ( "banana-eaters"), which includes plantain-eaters and go-away-birds. In southern Africa both turacos and go-away-birds are commonly known as loeries. They are semi-zygodactylous: the fourth ( ...
s).
Structural coloration
Structural coloration in animals, and a few plants, is the production of colour by microscopically structured surfaces fine enough to interfere with visible light instead of pigments, although some structural coloration occurs in combination wi ...
[ is involved in the production of blue colors, iridescence, most ]ultraviolet
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation ...
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''), also known as the common parakeet or shell parakeet, is a small, long-tailed, seed-eating parrot usually nicknamed the budgie ( ), or in American English, the parakeet. Budgies are the only spe ...
s).
The blues and bright greens of many parrot
Parrots, also known as psittacines (), are birds of the roughly 398 species in 92 genera comprising the order Psittaciformes (), found mostly in tropical and subtropical regions. The order is subdivided into three superfamilies: the Psittacoide ...
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 possessed by the majority of birds used to distribute the gland's oil through the plumage by means of preening. It is located dorsally at th ...
, 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 rule
Gloger'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. It was named after the zoologist Constantin Wilhelm Lambe ...
.
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 ( : lice) is the common name for any member of the clade Phthiraptera, which contains nearly 5,000 species of wingless parasitic insects. Phthiraptera has variously been recognized as an order, infraorder, or a parvorder, as a result of ...
) 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
Phoresis or phoresy is a non-permanent, commensalistic interaction in which one organism (a phoront or phoretic) attaches itself to another (the host) solely for the purpose of travel. Phoresis has been observed directly in ticks and mites s ...
. 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 in the world. In fact, it appears to have the largest natural distribution of any of the world's passerines, ranging over 251 million square kilometres globally. ...
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 preening
Preening is a found in birds that involves the use of the beak to position feathers, interlock feather that have become separated, clean plumage, and keep ectoparasites in check. Feathers contribute significantly to a bird's insulation, waterp ...
and bathing in water or dust
Dust is made of fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian process), volcanic eruptions, and pollution. Dust in ho ...
. 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-shaped aerodynamic stabilization device attached on arrows, bolts, darts, or javelins, and are typically made from light semi-flexible materials such as feathers or bark. Each piece of such fin is a fletch, also known as a ...
arrows. Colorful feathers such as those belonging to pheasant
Pheasants ( ) are birds of several genera within the family Phasianidae in the order Galliformes. Although they can be found all over the world in introduced (and captive) populations, the pheasant genera native range is restricted to Eurasia ...
s have been used to decorate fishing lure
A fishing lure is a broad type of artificial angling baits that are replicas designed to mimic real prey animals and attract the attention of predatory fish, using appearances, flashy colors, bright reflections, movements, vibrations and/or loud ...
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 bird or bat) and a moving vehicle, usually an aircraft. The term ...
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, biodegradable 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 of the family Accipitridae. Eagles belong to several groups of genera, some of which are closely related. Most of the 68 species of eagle are from Eurasia and Africa. Outside this area, j ...
feathers have great cultural and spiritual value to American Indians in the US and First Nations
First Nations or first peoples may refer to:
* Indigenous peoples, for ethnic groups who are the earliest known inhabitants of an area.
Indigenous groups
*First Nations is commonly used to describe some Indigenous groups including:
**First Natio ...
peoples in Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
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
Condor is the common name for two species of New World vultures, each in a monotypic genus. The name derives from the Quechua ''kuntur''. They are the largest flying land birds in the Western Hemisphere.
They are:
* The Andean condor (''Vu ...
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 native to the Indian subcontinent. It has been introduced to many other countries. Male peafowl are referred to as peacocks, and ...
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. The Clan Campbell lands are in Argyll and within their lands lies Ben Cruachan. The ...
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, an armiger is a person entitled to use a heraldic achievement (e.g., bear arms, an "armour-bearer") either by hereditary right, grant, matriculation, or assumption of arms. Such a person is said to be armigerous. A family or a cl ...
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 that emerged and developed in the United Kingdom and the British Empire throughout the Victorian era, roughly from the 1830s through the 1890s. The period saw ...
). 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 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 singing bird concealed below an oval lid and activated by means of an operating lever.
Its origins are ...
es. This trade caused severe losses to bird populations (for example, egret
Egrets ( ) are herons, generally long-legged wading birds, 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 ...
s and whooping crane
The whooping crane (''Grus americana'') is the tallest North American bird, named for its whooping sound. It is an endangered crane species. Along with the sandhill crane (''Antigone canadensis''), it is one of only two crane species native to ...
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 is a conservation law in the United States that prohibits trade in wildlife, fish, and plants that have been illegally taken, possessed, transported, or sold.United States. Lacey Act (Game). , ch. 553. Approved May 25, 1900. ...
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 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 groomi ...
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
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, 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), an object defined on a set of points
* Scale (ratio), the ratio of a linear dimension of a model to the corresponding dimension of the original
* Scale factor, a number w ...
, there are numerous objections to that idea, and more recent explanations have arisen from the paradigm of evolutionary developmental biology. 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 in which members of one biological sex choose mates of the other sex to mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex ( ...
. In fossil specimens of the paravian ''Anchiornis huxleyi
''Anchiornis'' is a genus of small, four-winged paravian dinosaurs, with only one known species, the type species ''Anchiornis huxleyi'', named for its similarity to modern birds. The Latin name ''Anchiornis'' derives from a Greek word meaning " ...
'' and the pterosaur
Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 ...
'' Tupandactylus imperator'', the features are so well preserved that the melanosome
A melanosome is an organelle found in animal cells and is the site for synthesis, storage and transport of melanin, the most common light-absorbing pigment found in the animal kingdom. Melanosomes are responsible for color and photoprotection i ...
(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. ''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. Additionally, when comparing different '' 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.
Molecular evolution
Several gene
In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
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, Zic1
ZIC1 is a member of the ''Zi''nc finger of the ''c''erebellum (ZIC) protein family.
ZIC1 is classified as a ZIC protein due to conservation of the five C2H2 zinc fingers, which enables the protein to interact with DNA and proteins. ZIC1 is found ...
, Grem1
Gremlin is an inhibitor in the TGF beta signaling pathway. It primarily inhibits bone morphogenesis and is implicated in disorders of increased bone formation and several cancers.
Structure
Gremlin1, previously known as Drm, is a highly con ...
, Spry2
Sprouty homolog 2 (Drosophila), also known as SPRY2, is a protein which in humans is encoded by the ''SPRY2'' gene.
Function
This gene encodes a protein belonging to the sprouty family. The encoded protein contains a carboxyl-terminal cysteine- ...
, and Sox18
Transcription factor SOX-18 is a protein that in humans is encoded by the ''SOX18'' gene.
Function
This gene encodes a member of the SOX (SRY-related HMG-box) family of transcription factors involved in the regulation of embryonic development ...
.
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 (α-keratin) is a type of keratin found in vertebrates. It is the key structural material making up scales, hair, nails, feathers, ho ...
, 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
The American alligator (''Alligator mississippiensis''), sometimes referred to colloquially as a gator or common alligator, is a large crocodilian reptile native to the Southeastern United States. It is one of the two extant species in the gen ...
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 crocodilians 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. 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. 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.
Feathered dinosaurs
Several non-avian dinosaurs had feathers on their limbs that would not have functioned for flight.[ One theory suggests that feathers originally evolved on dinosaurs due to their ]insulation
Insulation may refer to:
Thermal
* Thermal insulation, use of materials to reduce rates of heat transfer
** List of insulation materials
** Building insulation, thermal insulation added to buildings for comfort and energy efficiency
*** Insulated ...
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
''Microraptor'' (Greek, μικρός, ''mīkros'': "small"; Latin, ''raptor'': "one who seizes") is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China. They ...
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 of small, feathered, maniraptoran dinosaur from the Daohugou Beds in China. It is possibly older than ''Archaeopteryx'', though the age of the Daohugou Beds where it was found is debated. A maj ...
daohugouensis'' and ''Dilong paradoxus
''Dilong'' (帝龍, which means 'emperor dragon') is a genus of basal tyrannosauroid dinosaur. The only species is ''Dilong paradoxus''. It is from the Lower Cretaceous Yixian Formation near Lujiatun, Beipiao, in the western Liaoning province ...
'', a tyrannosauroid
Tyrannosauroidea (meaning 'tyrant lizard forms') is a superfamily (or clade) of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent b ...
which is 60 to 70 million years older than ''Tyrannosaurus rex
''Tyrannosaurus'' is a genus of large 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. ''Tyrannosaurus'' live ...
.''
The majority of dinosaurs known to have had feathers or protofeathers are theropods
Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally ca ...
, however featherlike "filamentous integumentary structures" are also known from the ornithischian
Ornithischia () is an extinct order of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name ''Ornithischia'', or "bird-hipped", reflects this similarity and is derived from the Greek st ...
dinosaurs '' 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 ...
''. 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, a basal neornithischian from the Middle Jurassic. The first ''Kulindadromeus'' fossil was found in Russia. Its feather-like integument is evidence for protofeathers being basal to Ornithischia and p ...
'' was reported as having structures resembling stage-3 feathers. The likelihood of scales evolving on early dinosaur ancestors are high. However, this was by assuming that primitive pterosaurs were scaly. 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 Congo peafowl (''Afropavo congensis''), also known as the African peafowl or ''mbulu'' by the Bakôngo, is a species of peafowl native to the Congo Basin. It is one of three peafowl species and the only member of the subfamily Pavoninae nat ...
, the beard of the turkey
Turkey ( tr, Türkiye ), officially the Republic of Türkiye ( tr, Türkiye Cumhuriyeti, links=no ), is a transcontinental country located mainly on the Anatolian Peninsula in Western Asia, with a small portion on the Balkan Peninsula in ...
, and the spine on the head of the horned screamer
The horned screamer (''Anhima cornuta'') is a member of a small family of birds, the Anhimidae, which occurs in wetlands of tropical South America. There are three screamer species, the other two being the southern screamer and the northern scr ...
. A reestimation of maximum likelihoods by paleontologist Thomas Holtz
Thomas Richard Holtz Jr. (born September 13, 1965) is an American vertebrate palaeontologist, author, and principal lecturer at the University of Maryland's Department of Geology. He has published extensively on the phylogeny, morphology, ecomorp ...
finds that filaments were more likely to be the ancestral state of dinosaurs.
In 2010, a carcharodontosaurid
Carcharodontosauridae (carcharodontosaurids; from the Greek καρχαροδοντόσαυρος, ''carcharodontósauros'': "shark-toothed lizards") is a group of carnivorous theropod dinosaurs. In 1931, Ernst Stromer named Carcharodontosauridae ...
named ''Concavenator corcovatus'' was found to have remiges
Flight feathers (''Pennae volatus'') are the long, stiff, asymmetrically shaped, but symmetrically paired pennaceous feathers on the wings or tail of a bird; those on the wings are called remiges (), singular remex (), while those on the tai ...
on the ulna suggesting it might have had quill-like structures on the ams. However, Foth et al. 2014 disagress 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. 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.
Since the 1990s, dozens of feathered dinosaurs have been discovered in the clade Maniraptora
Maniraptora is a clade of coelurosaurian dinosaurs which includes the birds and the non-avian dinosaurs that were more closely related to them than to ''Ornithomimus velox''. It contains the major subgroups Avialae, Deinonychosauria, Oviraptoros ...
, 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 and North America. They are distinct for their characteristically short, beaked, parrot-like skulls, with or wi ...
and Deinonychosauria
Deinonychosauria is a clade of paravian dinosaurs which lived from the Late Jurassic to the Late Cretaceous periods. Fossils have been found across the globe in North America, Europe, Africa, Asia, South America, and Antarctica,Case, J.A., Mar ...
. 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 clade of bird-like theropod dinosaurs. During most of the 20th century, troodontid fossils were few and incomplete and they have therefore been allied, at various times, with many dinosaurian lineages. More recent fossil discov ...
and Dromaeosauridae
Dromaeosauridae () is a family of feathered theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek ('), meaning ...
. 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''—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 existed in some bird predecessors. The wings most probably belonged to enantiornithes, a diverse group of avian dinosaurs.
A large phylogenetic
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...
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
Ornithoscelida () is a proposed clade that includes various major groupings of dinosaurs. An order Ornithoscelida was originally proposed by Thomas Henry Huxley but later abandoned in favor of Harry Govier Seeley's division of Dinosauria into Sau ...
. 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 Middle Triassic is the second of three epochs of the Triassic period or the middle of three series in which the Triassic system is divided in chronostratigraphy. The Middle Triassic spans the time between Ma and ...
, though this has been disagreed upon. The lack of feathers present in large sauropods and ankylosaurs could be that feathers were suppressed by genomic regulators.
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) 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") is an extinct clade of flying reptiles in the order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 ...
s were long known to have filamentous fur-like structures covering their body known as pycnofibres
Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 ...
, 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
The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...
of Inner Mongolia
Inner Mongolia, officially the Inner Mongolia Autonomous Region, is an autonomous region of the People's Republic of China. Its border includes most of the length of China's border with the country of Mongolia. Inner Mongolia also accounts for a ...
, 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
Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...
. 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
Anurognathidae is a family of small, short-tailed pterosaurs that lived in Europe, Asia, and possibly North America during the Jurassic and Cretaceous periods. Five genera are known: ''Anurognathus'', from the Late Jurassic of Germany; ''Jeholopt ...
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.
''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
The down of birds is a layer of fine feathers found under the tougher exterior feathers. Very young birds are clad only in down. Powder down is a specialized type of down found only in a few groups of birds. Down is a fine thermal insulator an ...
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
A melanosome is an organelle found in animal cells and is the site for synthesis, storage and transport of melanin, the most common light-absorbing pigment found in the animal kingdom. Melanosomes are responsible for color and photoprotection i ...
pigments identified in other fossil integuments, specifically phaeomelanosomes. Furthermore, infrared spectral analysis of these pycnofibres show similar absorption spectra
Absorption spectroscopy refers to spectroscopic techniques that measure the absorption of radiation, as a function of frequency or wavelength, due to its interaction with a sample. The sample absorbs energy, i.e., photons, from the radiating ...
to red human hair
Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals.
The human body, apart from areas of glabrous skin, is covered in follicles which produce thick terminal and fine ...
. These pycnofibres likely provided both insulation and may have helped streamline the body and wings during flight.
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. 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. 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.
See also
* Feather development
Feather development occurs in the epidermal layer of the skin in birds. It is a complicated process involving many steps. Once the feathers are fully developed, there are six different types of feathers: contour, flight, down, filoplumes, semi ...
* Delayed feathering in chickens
Delayed-feathering in chickens is a genetically determined delay in the first weeks of feather growing, which occurs normally among the chicks of many chicken breeds and no longer manifests itself once the chicken completes adult plumage.
The di ...
* Hen feathering in cocks
* Imping
Imping is the practice of replacing a broken feather of a bird with another one, referred to as a donor feather, from a previous Moulting, molt of the same animal or from another animal of the same or of a different species. Imping is mostly done ...
* List of poultry feathers
Some terms used for the feathers of poultry are identical to those used for feathers of other birds, while others are specific to poultry. They include:
See also
* Bird anatomy
* Feather
* Flight feather
* List of chicken colours
Breeders ...
* Pinioning
Pinioning is the act of surgically removing one pinion joint, the joint of a bird's wing farthest from the body, to prevent flight. Pinioning is often done to waterfowl and poultry. It is not typically done to companion bird species such as parrot ...
* Plumage
* White feather
The white feather is a widely recognised propaganda symbol. It has, among other things, represented cowardice or conscientious pacifism; as in A. E. W. Mason's 1902 book, '' The Four Feathers''. In Britain during the First World War it was of ...
References
Further reading
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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
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