Glossary of bird terms

Birds are amazing creatures that belong to the class Aves. They are the only living dinosaurs and have special features like feathers [/w/2] that help them fly [/w/3], though some, like flightless birds [/w/4], cannot. Birds have beaked [/w/5] jaws [/w/6], lay [/w/7] hard-shelled [/w/8] eggs, and have a high metabolic [/w/9] rate, a four-chambered heart [/w/10], and a strong yet lightweight skeleton [/w/11].

Scientists and bird lovers use many special words to describe birds. These words talk about things like the shape of a bird's body, the different kinds of feathers it has, such as filoplume [/w/15], pennaceous [/w/16], and plumulaceous [/w/17] feathers, and how those feathers grow and change. There are even words for the tiny parts of feathers, like barbules [/w/12], rachides [/w/13], and vanes [/w/14].

This glossary explains many of these special words that people use when they talk about birds. It focuses on words that apply to many different kinds of birds, not just one species. Even common words like "back" [/w/22] or "belly" [/w/23] are explained as they relate to a bird's unique body, sometimes called its "topography" [/w/25]. This way, anyone interested in birds can better understand what they are seeing when they watch or read about these fascinating animals.

A

addled eggs

Also known as wind eggs or hypanema, these are eggs that cannot hatch. See related: overbrooding.

afterfeather

These are small structures that grow from the base of a bird's feather. They help keep the bird's feathers warm. Some birds, like pigeons and doves, do not have afterfeathers.

allopreening

Main article: Preening § Allopreening

This is when birds clean each other. One bird might clean another, or they might clean each other at the same time. This can help show that they are friendly to each other.

alternate plumage

Also called nuptial plumage or breeding plumage, this is the special set of feathers birds wear during their breeding season. These feathers are often brighter than their usual ones, to help attract mates. They grow after a special feather change called a prealternate moult.

altricial

Main article: Altricial

These are baby birds that hatch with their eyes closed, with very little fur, and cannot take care of themselves. They need their parents to keep them warm and bring them food. Other baby birds, called precocial, can walk and see right away.

alula

Main article: Alula

Also known as a bastard wing, this is a small "thumb" on a bird's wing. It helps the bird fly slowly and land without falling. It has a few small feathers that help with this.

anisodactylous

This describes birds with four toes: three point forward, and one points backward. Most songbirds are anisodactylous.

anting

Main article: Anting (bird activity)

Some birds rub ants or other small insects on their feathers. This might help keep their feathers clean or make the insects taste better. Over 200 bird species do this.

apical spot

This is a small mark near the end of a feather.

apterylae

These are areas on a bird's skin without feathers. They are found between the areas where feathers grow.

aviculture

Main article: Aviculture

This is the practice of keeping birds in captivity and breeding them.

axilla

Also called the axillar region, "underarm", or "armpit", this is the area on a bird that is like an armpit. It often has special feathers called axillaries.

axillaries

Also known as axillary feathers or lower humeral coverts, these are special feathers found in the armpit area of a bird. They are usually long, stiff, and white.

B

The word "back" describes the upper part of a bird between the mantle and the rump.

A "barb" is a part of a feather that grows from the central shaft. Barbules are tiny structures that branch off from the barb, helping the feather stay strong and flexible.

During the time when birds are not breeding, their feathers may look duller. This is called basic plumage.

The beak is a bird's nose and mouth all in one. It is used for eating, finding food, and even showing affection to a mate. Beaks come in many shapes and sizes, but they all have two parts: the upper and lower mandible, covered in a tough material called keratin.

Beak colour can change depending on the bird's hormones and what it eats. It is often brightest when the breeding season is near.

The belly of a bird is the area on its underparts between the breast and the vent.

When birds are mated, they often touch or clasp each other's beaks. This is called billing and helps strengthen their bond.

Bird ringing, also known as bird banding, is when small numbered tags are placed on a bird's leg or wing. This helps scientists track where birds go and how they live.

Body down is the soft, fluffy layer of feathers that lies under the outer feathers on a bird's body.

The breast of a bird is the area between the throat and the belly.

A brood is all the young birds from one nesting attempt. Brooding is when a bird sits on its eggs to keep them warm until they hatch. Some birds, called brood parasites, lay their eggs in other birds' nests and let those birds raise their young.

C

Plural: calami. The basal part of the quill of pennaceous feathers, which embeds at its proximal tip in the skin of a bird. The calamus is hollow and has pith formed from the dry remains of the feather pulp. The calamus stretches between two openings—at its base is the inferior umbilicus and at its distal end is the superior umbilicus; the rachis of the stem, hosting the vanes, continues above it.

Call

Main article: Bird vocalization

Specific types: alarm; contact; duet; antiphonal duetting; food begging; flight; mobbing. A type of bird sound used for giving alarms or keeping members of a flock together—as opposed to a bird's song, which is longer, more complex and is usually associated with courtship and mating. Individual birds may be sensitive enough to identify each other through their calls. Many birds that nest in colonies can locate their chicks using their calls. Alarm calls are used to sound alarm to other individuals. Food-begging calls are made by baby birds to beg for food. Mobbing calls signal other individuals in mobbing species while harassing a predator.

Canopy feeding

Also defined: double-wing feeding. Some herons, such as the black heron, adopt an unusual position while hunting for prey. With their head held down in a hunting position, they sweep their wings forward to meet in front of their head, thereby forming an umbrella shaped canopy. One theory about the function of this behaviour is that it reduces glare from the water surface, allowing the bird to more easily locate and catch prey. Alternatively, the shade provided by the canopy may attract fish making their capture easier.

Carpal bar

A patch seen on the upperwing of some birds that usually appears as a long stripe or line. It is created by the contrast between the greater coverts and the other wing feathers.

Caruncle

The collective term for the several fleshy protuberances on the heads and throats of gallinaceous birds, i.e., combs, wattles, ear lobes and nodules. They can be present on the head, neck, throat, cheeks or around the eyes of some birds. Caruncles may be featherless, or present with a small array of scattered feathers. In some species, they may form pendulous structures of erectile tissue, such as the "snood" of the domestic turkey. While caruncles are ornamental elements used by males to attract females to breed, it has been proposed that these organs are also associated with genes that encode resistance to disease.

Casque

Main article: Casque (anatomy)

A horny ridge found on the upper mandible of a bird's bill, especially used in relation to hornbills and cassowaries, though other birds may have casques such as common moorhens, tufted puffins and (male) friarbirds. The ridge line on the upper maxilla may extend to a prominent crest on the front of the face and on the head. Some hornbill casques contain a hollow space that may act as a resonance chamber.

Cere

Main article: Beak § Cere

From the Latin cera meaning 'wax', a waxy structure which covers the base of the bills of some bird species from a handful of families—including raptors, owls, skuas, parrots, turkeys and curassows. The cere structure typically contains the nares, except in owls, where the nares are distal to the cere. Although it is sometimes feathered in parrots, the cere is typically bare and often brightly coloured. In raptors, the cere is a signal which indicates the "quality" of a bird. The colour or appearance of the cere can be used to distinguish between males and females in some species.

Cheek

Also, malar / malar region. The area of the sides of a bird's head, behind and below the eyes.

Chin

A small feathered area located just below the base of the bill's lower mandible.

Cloaca

A multi-purpose opening terminating at the vent at the posterior of a bird: birds expel waste from it; most birds mate by joining cloaca; and females lay eggs from it. Birds do not have a urinary bladder or external urethral opening and (with exception of the ostrich) uric acid is excreted from the cloaca, along with faeces, as a semisolid waste. Additionally, in those few bird species in which males possess a penis, it is hidden within the proctodeum compartment within the cloaca, just inside the vent.

Cloacal kiss

Most male birds lack a phallus and instead have erectile genital papilla at the terminus of their vas deferens. When male and female birds of such species come together, they each evert and then press together their respective proctodeum.

Clutch

Main article: Clutch (eggs)

All of the eggs produced by birds often at a single time in a nest. Clutch size differs greatly between species, sometimes even within the same genus. It may also differ within species due to many factors including habitat, health, nutrition, predation pressures and time of year. Average clutch size ranges from one (as in northern gannet) to about 17 (as in grey partridge).

Comb

Main article: Comb (anatomy)

Also, cockscomb (coxcomb and other sp. variants). A fleshy growth or crest on the top of the head of gallinaceous birds, such as turkeys, pheasants and domestic chickens. Its alternative name, cockscomb (or coxcomb) reflects that combs are generally larger on males than on females. Comb shape varies considerably depending on the breed or species of bird. The "comb" most often refers to chickens in which the most common shape is the "single comb" of a rooster from breeds such as the leghorn. Other common comb types are the "rose comb" of, e.g., the eponymous rosecomb; the "pea comb" of, e.g., the brahma and araucana; and others.

Colony

Main articles: Bird colony, Communal roosting, Heronry, and Rookery

Also defined: seabird colony; breeding colony; communal roost; heronries; rookery. A large gathering of individuals of one or more species of bird that nest or roost in proximity at a particular location. Many kinds of birds are known to gather in groups of varying size; a gathering of nesting birds is called a breeding colony. A group of birds gathering for rest is called a communal roost. Approximately 13% of all bird species nest colonially. Nesting colonies are very common among seabirds on cliffs and islands. Nearly 95% of seabirds are colonial, leading to the usage, seabird colony, sometimes called a rookery. Many species of terns nest in colonies on the ground. Herons, egrets, storks and other large waterfowl also nest together in what are called heronries.

Colour morph

See morph.

Commissure

Depending on usage, may refer to the junction of the upper and lower mandibles, or alternately, to the full-length apposition of the closed mandibles, from the corners of the mouth to the tip of the beak.

Corpuscles of Herbst

Nerve-endings similar to the Pacinian corpuscle, found in the mucous membrane of the tongue, in pits on the beak and in other parts of the bodies of birds. They differ from Pacinian corpuscles in being smaller and more elongated, in having thinner and more closely placed capsules and in that the axis-cylinder in the central clear space is encircled by a continuous row of nuclei.

Coverts

Main article: Covert feather

Also, covert feathers; tectrices – singular: tectrix. A layer of non-flight feathers overlaying and protecting the quills of flight feathers. At least one layer of covert feathers appear both above and beneath the flight feathers of the wings as well as above and below the rectrices of the tail. These feathers may vary widely in size.

Cranial kinesis

Also defined: prokinesis, amphikinesis and distal rhynchokinesis. Movement of the upper mandible in relation to the front of the skull. There is very little of this movement in birds that feed primarily through grazing and thus do not need to open their bills very widely. This is in contrast to parrots, which use their bills to manipulate food and as a support when climbing trees. There are multiple types of cranial kinesis: prokinesis, where the bill moves only at the craniofacial hinge; amphikinesis, where the whole upper jaw is raised; and distal rhynchokinesis, where the bill flexes somewhere along the length of the bill, compared to just at the base.

Crest feather

Main article: Crest (feathers)

Collectively, the/a crest. Long crest feathers are sometimes called quill feathers. Also defined: recumbent crests and recursive crests. A type of semiplume feather with a long rachis with barbs on either side, that often presents as a prominent tuft on the crown and (or through) the neck and upper back. Birds with crests include Victoria crowned pigeons, northern lapwings, macaroni penguins and others, but the most recognizable are cockatoos and cockatiels, which can raise or lower their crests at will and use them to communicate with fellow members of their species, or as a form of defence to frighten away other species that approach too closely. In some species the position of the crest is a threat signal that can be used to predict behaviour. In Steller's jays, for example, a raised crest indicates a likelihood of attack, and a lowered crest indicates a likelihood of retreat. Crests can be recumbent or recursive, depending on the species. The recumbent crest, such as in white cockatoos, has feathers that are straight and lie down essentially flat on the head until fanned out. The recursive crest, such as in sulphur-crested cockatoos and Major Mitchell's cockatoos, is noticeable even when its feathers are not fanned out because they curve upward at the tips even when lying flat, and when standing up, often bend slightly forward toward the front of the head.

Crissum

The feathered area between the vent and the tail. Also, the collective name for the undertail coverts.

Crop

Main article: Crop (anatomy) § Birds

An expanded, muscular pouch near the gullet or throat found in some but not all birds. It is a part of the digestive tract, essentially an enlarged part of the esophagus, used for the storage of food prior to digestion. In adult doves and pigeons, the crop can produce crop milk to feed newly-hatched chicks.

Crop milk

Main article: Crop milk

A secretion from the lining of the crop of parent birds that is regurgitated to young birds. It is found among all pigeons and doves. An analogue to crop milk is also secreted from the esophagus of flamingos and some penguins. Crop milk bears little physical resemblance to mammalian milk, the former being a semi-solid substance somewhat like pale yellow cottage cheese. It is extremely high in protein and fat, containing higher levels than cow or human milk and has been shown to also contain antioxidants and immune-enhancing factors.

Crown

Also defined: occiput / hindhead. The portion of a bird's head found between the forehead—demarcated by an imaginary line drawn from the anterior corners of the eyes—and through the "remainder of the upper part of the head", to the superciliary line. The occiput or hindhead, is the posterior part of the crown.

Cryptic plumage

Also defined: phaneric plumage. Plumage of a bird that is camouflaging. For example, the white winter plumage of ptarmigans is cryptic as it serves to conceal it in snowy environments.

Culmen

Main article: Beak § Culmen

The dorsal ridge of the upper mandible. Likened by ornithologist Elliott Coues to the ridge line of a roof, it is the "highest middle lengthwise line of the bill" and runs from the point where the upper mandible emerges from the forehead's feathers to its tip. The bill's length along the culmen is one of the regular measurements made during bird ringing and is particularly useful in feeding studies. The shape or colour of the culmen can also help with the identification of birds in the field.

D

Birds have special feathers and ways to describe their looks and behaviors.

Definitive plumage is when an adult bird's feathers are fully developed and look the same no matter their age.

Some birds, like loons, grebes, pelicans, hawks, and eagles, are missing a certain feather on their wings called a fifth secondary feather.

Birds can also be grouped by what they eat. Words like insectivore (eats insects) or nectarivore (drinks nectar) describe a bird's main food. Their beaks and other body parts often match what they eat.

Some birds, like certain owls and gulls, dive into water to catch food. There are two kinds of diving: surface diving, where birds dive from the water's surface, and plunge diving, where they dive from the air above.

Down feathers are soft, fluffy feathers under a bird's tougher outer feathers. They help keep the bird warm and, for water birds, help them float. Young birds are often covered in down feathers when they first hatch.

Some birds, like woodpeckers, communicate by drumming on hard surfaces with their beaks. This drumming can tell other birds about their territory.

E

ear-coverts

Small covert feathers located behind a bird's eye, in one to four rows, which cover the ear opening (bird ears have no external features) and may aid in the acuity of bird hearing.

egg

Main article: Egg

Also defined: eggshell; yolk; albumen; chalaza. The organic vessel containing the zygote, in which birds develop until hatching. Eggs are usually oval in shape, and have a base white colour from the predominant calcium carbonate makeup of the outer shell, called the eggshell, though passerine birds especially may have eggs of other colours, such as through deposition of biliverdin and its zinc chelate, which give a green or blue ground colour, and protoporphyrin which produces reds and browns. A viable bird egg (as opposed to a non-viable egg: see addled eggs) consists of a number of structures. The eggshell is 95–97% calcium carbonate crystals, at least in chickens, stabilized by a protein matrix, without which the crystalline structure would be too brittle to keep its form; the organic matrix is thought to have a role in deposition of calcium during the mineralization process. The structure and composition of the avian eggshell serves to protect the egg against damage and microbial contamination, prevention of desiccation, regulation of gas and water exchange for the growing embryo and provides calcium for embryogenesis. Inside the eggshell are two shell membranes (inner and outer), and at the center is a yolk—a spherical structure, usually some shade of yellow, to which the fertilized gamete attaches and which the embryonic bird uses as sustenance as it grows. The yolk is suspended in the albumen (also called egg white or glair / glaire) by one or two spiral bands of tissue called the chalazae. The albumen protects the yolk and provides additional nutrition for the embryo's growth, though it is made up of approximately 90% water in most birds. Prior to fertilization, the yolk is a single cell ovum or egg cell; one of the few single cells that can be seen by the naked eye.

egg binding

Main article: Egg binding

An egg that while traversing the reproductive tract during the process of being laid, becomes stuck near to the opening of the cloaca or further inside the oviduct. The condition may be caused by obesity, nutritional imbalances such as calcium deficiency, environmental stress such as temperature changes, or malformed eggs.

egg incubation

Main article: Egg incubation

Also, brooding. The general care of unhatched eggs by parent birds (more often by females but by birds of both sexes), especially by temperature regulation through sitting on them, crouching or squatting over them, covering them with their wings, providing shade, wetting eggs and related behaviours. The target temperature of most species is 37 °C (99 °F) to 38 °C (100 °F). In monogamous species incubation duties are often shared, whereas in polygamous species one parent is wholly responsible for incubation. Warmth from parents passes to the eggs through brood patches—areas of bare skin on the abdomen or breast of the incubating birds. Incubation can be an energetically demanding process; adult albatrosses, for instance, lose as much as 83 grams (2.9 oz) of body weight per day of incubation.

egg tooth

Main article: Beak § Egg tooth

A small, sharp, calcified projection on the beak that full-term chicks of most bird species have, which they use to chip their way out of their egg. This white spike is located near the tip of the upper mandible in most species (e.g., gulls); near the tip of the lower mandible instead in a minority of others, such as northern lapwings; with a few species, such as Eurasian whimbrels, black-winged stilts and semipalmated sandpipers, having one on each mandible. Despite its name, the projection is not an actual tooth (as the similarly-named projections of some reptiles are); instead, it is part of the integumentary system, as are claws and scales. The hatching chick first uses its egg tooth to break the membrane around an air chamber at the wide end of the egg. Then it pecks at the eggshell while turning slowly within the egg, eventually (over a period of hours or days) creating a series of small circular fractures in the shell. Once it has breached the egg's surface, the chick continues to chip at it until it has made a large hole. The weakened egg eventually shatters under the pressure of the bird's movements. The egg tooth is so critical to a successful escape from the egg that chicks of most species will perish unhatched if they fail to develop one.

emargination

Main article: Flight feather § Emargination

A pronounced narrowing at some variable distance along the feather edges at the outermost primaries of large soaring birds, particularly raptors. Whether these narrowings are called notches or emarginations' depends on the degree of their slope. An emargination is a gradual change, and can be found on either side of the feather. A notch is an abrupt change, and is only found on the wider trailing edge of the remige. The presence of notches and emarginations creates gaps at the wingtip; air is forced through these gaps, increasing the generation of lift.

eye-ring

Main article: Eye-ring

Also defined: orbital ring. A visible ring of feathers around a bird's eye; the eye-ring is often paler than the surrounding feathers. By contrast, an orbital ring is bare skin ringing the eye. In some species, such as little ringed plover, the orbital ring may be quite conspicuous.

eyestripe

Also, eye line / eyeline. A visible stripe on the feathers of a bird's head, often darker than the surrounding feathers, running through the eye region. Compare supercilium.

Eye features

[Blue-headed vireo](/wiki/Blue-headed_vireo), with a conspicuous [eye-ring](/wiki/Glossary_of_bird_terms#eye-ring)

[Little ringed plover](/wiki/Little_ringed_plover) chick, with a conspicuous [orbital ring](/wiki/Glossary_of_bird_terms#orbital_ring)

[White-eared sibia](/wiki/White-eared_sibia), with a conspicuous [eyestripe](/wiki/Glossary_of_bird_terms#eyestripe)

[Whinchat](/wiki/Whinchat), with a conspicuous [supercilium](/wiki/Glossary_of_bird_terms#supercilium) (eyebrow)

F

Feather
Main article: Feather

Feathers are special growths that cover birds' bodies. They help birds fly, keep them warm, and protect them. Feathers come in different types, like the ones on the outside of the body and softer ones underneath. They have a main stem with branches that help them overlap and stay in place.

Feather pecking
Main article: Feather pecking

Some birds, especially chickens raised for eggs, may peck at each other’s feathers. This can be gentle or more serious and is common in farm birds like chickens, turkeys, and ducks.

Feather-plucking
Main article: Feather-plucking

Feather-plucking is when a bird chews or pulls its own feathers, often seen in pets like parrots. It can damage their feathers and skin, and is common in birds that feel stressed or bored.

Fecal sac
Main article: Fecal sac

Some baby birds produce a special white or clear sac around their waste. This helps parent birds clean the nest easily. Not all birds do this, but many young birds show signs when they are ready to make one.

Filoplume
A type of soft, hair-like feather that grows with other feathers. These feathers help birds sense air movements and are often hidden by the main feathers.

Flange
A small part on bird feathers that helps them lock together tightly while flying.

Flanks
The area on a bird’s side, between its belly and back.

Fledge
When a young bird’s feathers and muscles are ready for flight, or when parents help their chicks reach this stage.

Fledgling
A young bird that has just learned to fly and is still learning to be independent.

Flight
Most birds can fly, which helps them find food, escape danger, and find mates. Birds have light bones, strong muscles, and special wings that help them soar. Some birds, like penguins, cannot fly but use similar movements to swim.

Flight feather
Main article: Flight feather

Long, strong feathers on a bird’s wings and tail that help it fly. Feathers on the tail are called rectrices, and those on the wings are called remiges.

Foot paddling
A behavior where gulls rapidly move their feet in water to bring up worms or other food.

Forehead
The part of a bird’s face above its bill, between the bill and the eyes.

Fovea
Main article: Fovea centralis

A special spot on a bird’s eye that helps it see clearly. Some birds, like hummingbirds, have two of these spots for even better vision.

Friction barbules
Special tiny parts on bird wings that help feathers grip together tightly while flying.

Frontal shield
Main article: Frontal shield

Some birds have a hard or soft plate on their forehead, often used for protection or showing off during courtship.

Furcula
Also, wishbone; merry-thought.
The furcula is a special forked bone near a bird’s neck, formed from two fused bones. It helps strengthen the bird’s skeleton for flight and aids in lifting the wings. It also helps with breathing by moving air through special sacs.

G

The gape is the inside of a bird's open mouth. The size of the gape can help determine what kind of food the bird eats.

The gape flange is where the top and bottom parts of a bird's beak meet. When baby birds, called chicks, are born, their gape flanges are soft. As they grow into young birds, called fledglings, the gape flanges stay a bit swollen. This helps tell if a bird is young. Parents also use the gape flanges as a target when feeding their chicks.

A gizzard is a special part of a bird's stomach. It has thick muscles and is used to grind up food. Birds often swallow small stones to help grind their food in the gizzard.

Gleaning is a way birds catch small animals, like insects, by picking them off surfaces. Birds might gleaning from leaves, the ground, or even from other animals. Some birds hover in the air while gleaning, while others move slowly and carefully.

The gnathotheca is a thin, horny covering on the lower part of a bird's beak.

Gonys are the lower ridge of a bird's beak, formed where the two sides of the beak meet.

The gonydeal angle is the point where the two sides of the beak meet at the end. It helps identify different bird species.

The gonydeal spot is a colored spot near the end of a bird's beak. In many birds, especially gulls, this spot is red or orange and encourages baby birds to ask for food.

A gorget is a colored patch of feathers on the throat or upper breast of some birds. Many male hummingbirds have iridescent gorgets.

Grooming refers to the process of preening, where birds clean their feathers.

The gular region is the back part of the underside of a bird's head, continuing from the chin.

Gular skin is the featherless skin in the gular region. In some birds, it forms a flap used to store food. In others, like frigatebirds, it can be inflated during courtship displays.

H

Main article: Bird feet and legs § Toes and unfused metatarsals

A bird's hallux is its rear-facing toe, also called the hind toe or first digit. In many birds, this is the only toe that points backward, such as in most passerine birds. Depending on where it attaches, the hallux can be incumbent (near the base of the metatarsus) or elevated (projecting from a higher part, as in rails).

The home range is the area where a bird spends most of its time. When a bird guards this area from others of the same species, it is called a territory. Territories can change with the seasons and may be used for different purposes like finding food or raising young. Larger birds usually have bigger home ranges, and carnivores often have larger ranges than other birds.

Main article: Humphrey–Parkes terminology

The Humphrey–Parkes terminology is a system for describing a bird's feathers. It was created in 1959 to make feather descriptions clearer. You can see how it differs from older ways of naming feathers in the entries for prealternate moult and prebasic moult.

The hyoid apparatus is a set of bones that helps a bird move its tongue. It includes the tongue bone and several other bones that let the tongue slide out smoothly. This apparatus is connected to the bird's voice box, or larynx.

I

The iris is the colored outer ring around a bird's eye, called the pupil. It can be many colors like brown, red, yellow, grey, or blue, and may change with the bird's age, sex, or type.

The inner wing is the part of a bird's wing closest to its body, stretching from where the wing connects to the body through the "wrist" joint. The rest of the wing, from the wrist to the tip, is called the outer wing.

Other terms include:

• inferior umbilicus or proximal umbilicus: a small opening at the base of a feather's shaft, embedded in the bird's skin.
• See also: pin feather, calamus, dermal, Malpighian layer, plasma, keratinous, superior umbilicus, pupil.

J

Main article: Jizz (birding)

Jizz is a fun word birdwatchers use to talk about the general feeling or look a bird gives you. It’s that special “vibe” you get when you see a bird, mixing things like its shape, how it moves, its size, colors, and even where it lives. For example, you might say, “This bird has the jizz of a thrush,” meaning it feels like a thrush even if you can’t see it clearly.

K

A keel is a special part of a bird's breastbone that helps it fly. It sticks out and gives the bird's wing muscles something strong to push against, which helps the bird move its wings well. Not all birds have a keel—birds that can't fly usually don't have one.

Some birds also show kleptoparasitism, which means they sometimes or often steal food from other birds. This can happen when a bird sees another one with food and takes it for itself.

Main article: Kleptoparasitism

L

A lateral throat-stripe is a dark line of color that runs along the side of a bird's neck, below its face markings.

A lek is when male birds gather in one spot to show off and attract females. They display their feathers and behaviors to try to win a mate. Sometimes these displays happen close together where the males can see each other, and other times they happen farther apart where the males can only hear each other.

The lore is the area on a bird's head between its eye and its beak.

The lower mandible is the bottom part of a bird's beak. It is made of special bones and is covered with a tough outer layer, helping the bird eat and explore its environment.

M

Birds have special ways to take care of themselves and their feathers. One important activity is called preening, where a bird cleans and arranges its feathers using its beak. Birds may also bathe in water or dust, stretch their bodies, or scratch themselves to stay comfortable. These activities help keep their feathers in good shape and their bodies healthy.

Many birds travel long distances each year in an activity called migration. In the spring, birds often fly north to find places to raise their families, and in the fall, they travel south to warmer areas where food is easier to find. These trips happen every year and are very important for the birds’ survival. Some birds travel in groups, which helps them save energy and stay safe.

N

A nail is a hard, horny plate at the tip of the beak in birds like ducks, geese, and swans. It helps them dig seeds out of mud or pry small animals from rocks. The nape is the back of the head, behind the top part. Nares are the two holes that lead to a bird's breathing system. Most birds have them near the base of the beak, but kiwis have them at the tip.

Natal down is the soft first layer of feathers that covers baby birds when they hatch. Some babies are already covered with it, while others grow it after hatching. Nests are where birds lay their eggs and care for their young. They can be simple depressions in the ground or complex structures made of twigs, mud, or other materials. Some birds, like hummingbirds, build very small nests, while others, like scrubfowl, build huge mounds.

A nictitating membrane is a third eyelid that moves across the eye to protect it and keep it moist. Most birds use this instead of blinking. Nidicolous birds stay in the nest after hatching and need to be fed by their parents. Nidifugous birds leave the nest soon after hatching and start exploring with their parents. Non-breeding plumage is the feathers birds wear when they are not raising young. A notch is a narrowing on the edge of a bird's wing feather, which helps with flying. Nuptial plumage is the special set of feathers birds show off when they are ready to mate.

O

Main article: oology

The scientific study of eggs looks at how birds lay and care for their eggs.

An operculum is a special flap above a bird's nose. In some birds, like those that dive into water, this flap helps keep water out of their noses while they swim.

Overbrooding happens when a bird keeps sitting on eggs that cannot hatch, even long after the usual time for them to hatch.

P

Passerine birds, also known as perching birds, belong to the order Passeriformes and make up more than half of all bird species. They are known for their unique toe arrangement—three pointing forward and one back—which helps them perch easily. These birds are very diverse and include many familiar species.

Pennaceous feathers, also called contour feathers, are a major type of feather found in most modern birds. They have a central shaft called a quill and are used for shaping the bird's body. Plumage refers to all the feathers covering a bird, and it can vary greatly in color and pattern between different species and even between males and females of the same species.

Q

A quartering is a way hunters train birds to fly slowly just above water or ground, looking for prey in open spaces.

A quill is the main stem of a feather. It includes parts like the shaft and the base where the feather grows. Experts sometimes use different meanings for this word, but it mainly refers to the feather’s strong central part.

R

The rachis is the upper part of a feather’s main shaft, stretching from near the base to the tip. It holds the feather’s vanes and helps the feather stay flexible for flight.

Rectrices are special feathers on a bird’s tail that help it slow down and steer while flying. Most birds have six pairs of these feathers, but some, like grebes and penguins, have fewer or none.

Remiges are the long, stiff feathers on a bird’s wings that help it fly. They are attached firmly to the wing bones and are usually the same size and shape on both wings.

Rictal bristles are stiff, hair-like feathers around a bird’s eyes and beak. They might help protect the eyes or sense nearby objects, especially for birds that catch insects.

A rosette is a fleshy bump found at the corners of the beaks of some birds, like puffins, and is part of their special feathers.

The rhamphotheca is the thin, horny outer layer covering a bird’s beak, made from a material called keratin.

The rump is the area at the back of a bird just before the tail starts. It often contains a special gland that produces oils for the bird’s feathers.

Main article: Flight feather § Rectrices

Main article: Flight feather § Remiges

S

Bird scales are made of keratin, like their beaks and claws, and are mostly found on their toes and lower legs. Unlike reptile scales, bird scales likely developed separately after feathers evolved. Bird embryos start with smooth skin, and scales form when the outer skin layer thickens and hardens on the feet.

Feathers covering a bird's scapula (upper back part of the wing) are called scapulars. Secondaries are a type of flight feather attached to the bird's forearm bone, helping create lift during flight. They are usually shorter and broader than the longest flight feathers, called primaries, and their number can vary greatly between species. Semiplumes are feathers that have features of both down feathers and contour feathers, helping to insulate and fill out a bird's plumage.

A patch of brightly colored feathers on the inner wing of some ducks, called a speculum, can also be found in certain parrots. Spurs are bony outgrowths covered in horn, found on the feet or legs of some birds. The sternum, or breastbone, looks different in flying birds compared to flightless birds. Birds make sounds using a special vocal organ called the syrinx, located where the windpipe splits into the lungs, allowing some birds to mimic human speech.

T

The term "tail" in birds mostly refers to the feathers at the end of their bodies and the shape they make. These feathers, called rectrices, often spread out like a fan.

Birds have sharp claws called talons, which are very important for birds that hunt. Some birds also use their claws to defend themselves. All birds have claws that help them grip things.

The lower part of a bird's leg, called the tarsus, includes the ankle and foot area. In birds, some bones in this area have fused together to form a single bone called the tarsometatarsus.

The throat of a bird is the feathered area between the chin and the upper breast. The topographical area between the "knee" and the body is called the thigh. The feathered part of the leg above the foot is the tibia.

The edges of a bird's upper and lower beak, called tomia, can vary. Some birds have special ridges or bristles along these edges to help them handle their food better. For example, seed-eating birds have ridges to slice through seed hulls, while insect-eating birds may have bristles to grip hard prey.

Torpor is a resting state used by some small birds to save energy. During torpor, birds become very inactive, lower their body temperature, and reduce their metabolism. This can happen daily for a few hours or during cold periods for much longer.

U

Covert feathers are special feathers that cover the base of a bird's tail on its underside. They help protect the tail. The underwing is the bottom side of a bird's wing, which you usually can't see when the wing is folded.

The upper part of a bird's beak, also called the maxilla, is supported by a special bone. It moves up and down, helping the bird eat and explore. The upper parts of a bird include areas above the eyes, like the crown, mantle, back, and parts of the wings. The under parts are all the areas on the underside of a bird, from the chin to the tail.

Uppertail coverts are feathers covering the base of the tail on the top side. In some birds, like peacocks, these feathers can be very long and beautiful. The upperwing is the top side of a bird's wing.

The uropygial gland, also called the preen gland or oil gland, is found at the base of a bird's tail. It makes oils that birds use to keep their feathers healthy and waterproof. This helps the feathers stay flexible and clean.

V

A vagrant bird is one found far outside its usual area. This can happen when a bird wanders beyond its normal home range during migration.

A vane is the flat, web-like part of a feather. It is made of tiny branches called barbs, which are connected by small hooks. This structure helps feathers overlap and stay in place.

Vent pecking is a problem seen in some farm birds, especially egg-laying hens. It happens when a bird pecks at another bird’s vent area, which is the opening near the tail. This behavior can hurt the other bird and is often seen after laying eggs.

Main article: Vent pecking

W

A wattle is a colorful flap of skin that hangs from a bird's head, often near the chin or throat. Birds like turkeys and guineafowls have wattles. Some birds perform whiffling, a flight behavior where they rapidly descend in a zig-zag pattern.

A wing bar is a stripe on a bird's upper wing made by the tips of certain feathers. It can change with the bird's seasonal feathers. Wing clipping is a practice where a bird's flight feathers are trimmed to keep it from flying, though it can sometimes cause injury.

Wing coverts are feathers that cover the wings, arranged in rows. They help protect the wing and shape its appearance. The wing formula is a way to measure and describe the shape of a bird's wing, useful for identifying species.

Wing lining refers to soft feathers along the front edge of the underside of a wing. Wings are the bird's forelimbs, essential for flight. They come in different shapes, such as elliptical for quick maneuvers, high speed for fast flight, high aspect ratio for gliding, and soaring wings for large birds.

The wingspan is the distance between the tips of a fully extended wing. The wandering albatross has the largest wingspan, while the bee hummingbird has the smallest. Winter plumage is the feathers birds wear during colder months.

Main article: Wing clipping

Main article: Flight feather § Wing formula

Z

Some birds have a special way of arranging their toes. This is called zygodactylous or yoke-toed. In these birds, two toes point forward and two toes point backward. You can see this in parrots, woodpeckers, and cuckoos. Usually, the second and third toes face forward, and the fourth toe and hallux face backward. But in trogons, it’s a bit different: the third and fourth toes face forward, and the second toe and hallux face backward. This different arrangement is called heterodactylous.