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This glossary contains terminology and definitions for birds in alphabetical order.


Abdomen

The abdomen is the ventral part of the bird, homologous to the human stomach region (also called the belly). It is comprised of the area between the vent and the posterior sternum. A bird will sleep with one foot tucked into its abdomen.

Alula

The alula is a small joint on the bird’s wing, similar to the human thumb, with three or four quill-like feathers attached. It is a necessity for low speed flight and maneuverability. The feathers function much like the slats on airplanes by basically increasing the camber of the wing and as such help the bird to land and take-off again.

Alular quills

Alular quills are three feathers attached to the alula originating from the base of the primaries. They are essential for low speed flight and aid in coordinated landing and take-off. See also Alula.

Alular quill coverts

Alular quill coverts are smaller feathers covering the quill of each flight feather. Each wing has primary, secondary and tertiary coverts based on the location of the feather.

Auricular

The auricular are the soft loose-webbed feathers on the side of the bird's head. These feathers overlap the ear and as such are also called ear coverts or ear path. They can sometimes be a different color depending on the bird species. Birds do not have ear lobes or external pinna like humans and other mammals; however they do have a slight thickening of the skin around the ear. See also Ear Patch.

Axillary

The axillary area is located between the body and the wing of the bird. In that sense, the axillary is similar to the human armpit, thus the other name "wingpit". The area is formally comprised of the underside base of the wing, extending to the ventral wing lining. Muscles in the area are heavily involved in flight.

Back

The back is the dorsal part of the bird between the bases of the wings and from the neck to the tail. It is homologous to the human back.

Belly

The belly is the ventral part of the bird; ie, the area between the flanks on each side and the crissum and breast. Flight muscles are located between the belly and the breast and most of the bird’s digestive organs are located in the belly. See also Abdomen.

Bill

Birds do not have a mouth like humans, but instead have a bill or a beak. The bill reveals much about the bird’s food and lifestyle. The bill is shaped such that the bird can optimally consume its food. For example, a toucan or a parrot has a strong hooked beak for cracking open hard nuts and removing tough skin from certain fruits.

Body

The body is homologous to the human torso. It is the bird’s main mass not including its appendages such as wings, tails and legs. The body contains all essential organs and a large part of the bird’s muscle mass.

Breast

The breast is the upper front part of a bird. Underneath the breast is where the major flight muscles are located which are then attached to the wings to help the bird lift its own weight. The muscles are attached to an enlarged breastplate which is a skeletal part unique to birds.

Breast band

The breast band is a colored stripe along the breast. Some birds do not have this distinction, but some species do. The colors and abundance signal to a potential mate how healthy the individual is and therefore whether he would be reproductively successful.

Breast spot

The breast spot is a small area on the breast that develops only in some adult birds.. It has a different color from the rest of the bird’s plumage.

Cap

The cap is the area on top of the head of the bird. In some species, this area is a different color; while in some cases it has the same color as the eye area. The color of the cap helps in differentiation between similar-looking but different species.

Cere

The cere is a smooth and featherless patch of skin located where the beak attaches to the forehead. It is often enlarged and brightly colored such as in parrots and in birds of prey. It is generally also called the operculum.

Cheek

The bird cheek is in the same location as the human cheek, between the lore, eye, auricular and the lower mandible.

Chest

The chest is analogous to the breast area; the frontal area on the body containing the breastplate and major flight muscles. See also Breast.

Chin

The chin is the general area of the face just below the bill. The bird’s chin does not protrude like a human’s chin and therefore is less prominent.

Cloaca

Birds do not have two separate cavities for excrement and reproduction like humans do. In birds, there is one entrance/exit that suits both functions. It is also called anus or vent.

Cloacal kiss

This term is analogous to sexual intercourse in humans. It is used to describe copulation between birds.

Collar

The collar is similar to the upper part of the human neck. It is located at the back of the crown.

Comb

The comb is only found in male birds and consists of a colored area over the eye. A well developed comb can also signal (sexual) health to a potential mate.

Commissure

The hinge where the mandibles meet is called the commissure. In most birds only the lower jaw can move, just like in humans. Some birds can move both mandibles, such as parrots.

Crest

the crests are the tuft on the head of the bird. They are larger in males than in females. Although they increase visibility to predators, they also increase visibility to a potential mate. The more elaborate the crest, the healthier the bird is and as such females can evaluate a potential mate by his crest.

Crissum

The crissum are feathers in a triangular area on the undersurface of a bird between its vent and the base of its tail feathers. One can tell whether a bird is adult or juvenile by looking at the crissum: Adult females tend to have conspicuous dusky edging to most of the feathers on the crissum; whereas juvenile females tend to have nearly pure white crissum.

Crown

The crown is the top part of the birds head. It can be the same color as the rest of the bird and holds a crest or cap, depending on the species.

Culmen

The culmen is the uppermost central ridge of the upper mandible. There is no specific function associated with it, but males tend to have a larger culmen than females.

Dihedral

When a bird in flight holds its wings such that they appear to form a “V” shape they are called dihedral. Generally, wings are held in this state when gliding.

Ear patch

The ear patch is a different term for auricular. It consists of soft, loose-webbed feathers on the side of the bird's head below and behind the eyes. These feathers overlap the ear and can be a different color depending on the bird species. Birds do not have ear lobes or external pinna like humans and other mammals; however they do have a slight thickening of the skin around the ear.

Ears

In birds, the ears are the rounded areas on the bird’s face, also called facial discs. They are not homologous to human ears. In certain cases, the ears can be of different size and in different places on the bird’s head, such as in owls. This allows for exact placement of sounds and also helps to focus sounds by funneling them into the ears.

Eye

The eye is the organ of sight. The bird's eyes are larger compared to the bird's skull and are, therefore, proportionally larger than human eyes. Since the skull is lighter compared to the human skull (adjusted for size), the eyes take up about 15% of the weight.

Eye line

The eye line is the line of feathers just in front and behind the eyes. It extends back from the posterior angle of the eye. This can be a useful trait used in identification in the field since it is very noticeable.

Eye ring

The eye ring can be visualized, in many different birds, as a pale ring of feathers encircling the eye. It is a very narrow ring which may not be very clear from a greater distance. Not all birds have an eye ring, but the blue-headed Vireo is an example of a bird with one.

Eyebrow

The eyebrow is used as a term to describe the arch of feathers growing overtop the bony arch of each eye in the same approximate location as the human eye brow. It is also called supercilium or superciliary line.

Eyelid

Birds have one upper and one lower eyelid - the latter being more moveable. Birds also have a nictitating membrane between both eyelids and the cornea. It has its own lubricating duct equivalent to the human tear duct to clean and protect the eye. Thus in total, birds have three eyelids.

Face

The face is homologous to the human face. It is the front part of the head consisting of the bill, eyes, cheeks and chin.

Facial discs

The facial discs are synonyms for ears. they are not homologous to human ears, in birds rather these are rounded areas on the bird’s face. In certain cases the ears can be of different size and in different places on the bird’s head, such as in owls. This allows for exact placement of sounds and also helps to focus sounds by funneling them into the ears.

Feet

The feet are located at the terminal part of the legs, just like in humans, and most birds have four toes. The first toe points backwards while the other three toes point forward. The second, third and fourth digits or toes are counted from the inside of the foot out and have 2, 3 and 4 phalanges respectively. Most birds do not have a fifth toe except for some where it has evolved into a defensive sput, such as in the chicken.

Flank

The flank is the lateral area posterior to the side of the bird’s body. It extends back the base of the tail.

Flank stripe

The flank stripe are the differently colored bands on the flanks. These can be used to differentiate bird species as they are quite visible from a distance.

Flight feathers

The flight feathers are those located on the wing, and are collectively called remiges (singular, remex). Flight feathers attach to the bones of the wing. The long stiff feathers are subdivided into two major groups based on the location of attachment- the primaries and secondaries..

Forehead
The forehead is homologous in location to the human forehead. It refers to the area above the eyes in the face of the bird.

Foreneck

The foreneck is similar to the human throat and is located in the front of the neck. It is often called jugulum or throat patch.

Frontal shield

The frontal shield is the area where the bill extends onto the forehead of the bird. It is often brightly colored and is meant to grab the attention of other birds.

Gape

The gape is a different word for commissure. it is the hinge where the mandibles meet. In most birds only the lower jaw can move, just like in humans. Some birds can move both mandibles, such as parrots. See also Commissure.

Gonys

The gonys is the lowermost ridge on the lower mandible. The gonys length is discriminating between different species and sexes.

Gorget

The gorget is the throat area of the bird. In this area for the hummingbird, it contains certain feathers that change color depending on the light striking it.

Greater secondary coverts

The greater secondary coverts are the feathers overlying the bases of the secondaries. In some birds, the primary converts are completely covered by them.

Gular region

The gular region is the area between the chin and the foreneck. In a pelican for example, the gular region is distended.

Head

The head is the upper part of the body, containing the bill, eyes, crown, ears and nose. It is homologous to the human head in terms of content and location.

Head stripes

The head stripes are the bold, bright colored lines on the top of the bird's head for certain species. This is a useful feature to discriminate between species. However, juvenile birds often have less pronounced stripes than adults have.

Hindhead

The hindhead is the back portion of the bird's crown. From this location certain species adorn elongated feathers. It is often also called the occiput.

Hindneck

The hindneck is the back of the neck, in the same relative location as in humans. Synonyms for the hindneck are also nape and collar.

Horns

The horns are paired contour feathers on top of the head of the bird. Often they are in bright colors and distinctive to the species.

Inner primaries

The inner primaries are a group of feathers closest to the body on the wing of the bird. They are generally covered partially by the secondaries.

Inner secondaries

The inner secondaries are groups of secondary feathers located closest to the body with respect to the outer secondary coverts.

Inner wing

The inner wing is similar to the inner arm of a human. It encompasses the shoulder, the secondaries and the secondary coverts.

Iris

The iris is the colored part of the eye, equal to the human iris, located around the pupil. The iris does not play a role in actual vision.

Jugulum

The jugulum is the ventral part of the neck under the bill. The juculum and the gular region comprises the throat. Other words used are foreneck or throatpatch. In the pelican the jugulum and gular region are distended.

Knee

The knee is the joint in the middle part of the leg, in the same location as the human knee.. Birds have strong leg bones and knees to take-off and land.

Leading edge of wing

The leading edge of the wing is the first from a frontal position when the bird is in flight. It is generally slightly curved and feathered.

Leg

The legs are limbs used for supporting the bird, homologous in function to the human legs.. Proportionally the bird’s legs are extremely strong in order for it to be able to land and take off without getting injured.

Lesser secondary coverts

The lesser secondary coverts are the relatively short feathers overlying the median secondary coverts on the top of the wing. They are located near the shoulder and can be seen as the “first row” of feathers on the bird’s wing. They are also called marginal coverts and are referred to as the shoulder.

Lore

The lore is the area under the eye and above the bill, similar to the area between the eyes and the nose in humans. The eye patch starts in this area for certain bird species.

Lower mandible

The lower mandible is the lower part of the bill and in many birds, this is the only part that moves. It is in function and location similar to the human’s lower jaw. Certain species, such as the parrot, are able to move both mandibles.

Lower mandibular tomia

The lower mandibular tomia is the cutting edge of the lower mandible, similar to the human teeth when looking at the skull only.

Malar stripe

The malar stripe is the area below the eye and bill and parallel to the throat. It is located on the sides of the chin and stretches downwards. Generally, the malar stripe is brightly colored. It is also called whisker, mustache or malar streak.

Mandibular ramus

The mandibular ramus is the prong-like projection from the bill on the posterior side. It is not present in all species.

Mantle

The mantle is the upper surface of the back and wings covered with shorter feathers. It is the area what would be covered with a coat if the bird were to wear one!

Marginal coverts

The marginal coverts are feathers overlying the base of the median secondary coverts and are also called lesser secondary coverts or shoulder. They are positioned at the top edge of the wing closest to the body of the bird.

Median line

For certain bird species, the median line is the stripe along the very top part of its head (through the crown).

Median secondary coverts

The median secondary coverts are feathers on the wing covering the bases of the greater secondary coverts. Their tips can often be a slightly lighter colored or white, giving the wing an illusion of being horizontally "striped".

Mustache

The mustache is a colorful area on each side of the chin moving down the throat area. It is also called malar streak or whisker.

Mouth

The mouth is similar in function to the human mouth and refers to the cavity bounded by the bill, homologous to the human mouth. Many bird species feed their young by ingesting the food and regurgitating it straight into the youngling's own mouth.

Nape

The nape is the back of the neck where the head joins the body. It is also called the hindneck or collar and is in the same relative location as the human neck. The collar is brightly colored in certain bird species.

Nasal canthus

The nasal canthus is the inner corner of the eye, the same location as the corner of the human eye closest to the nose. Nasal fossa
The nasal fossa is a depression in which the bird’s nostril is located. Generally, this area is located at the top of the bill and can be seen as two small punctures on the bill surface.

Neck

The neck connects the head to the body of the bird, homologous to the human neck. Different species have different neck lengths - the ostrich has many vertebrae in his neck area, while a hummingbird has significantly and visibly less. The neck allows the bird to move his head to increase its visual area without moving his body.

Neck patch

The neck patch is a sac located on the neck that is inflatable and is only visible in males during courtship.. During courtship, the male inflates this sac to impress the female.

Nictitating membrane

The nictitating membrane is the vertical semi-transparent fold under the eyelid. This is also the third eyelid of the bird and can be closed for protection. It has its own moisturizing system similar to tear ducts. It can be closed to protect the parent from their youngling’s sharp beaks.

Nostril

The nostrils are the two small punctures on the top of the bill.

Occiput

The occiput is the back portion of the birds crown. From this location, certain species adorn elongated feathers. It is also called the hindhead.

Operculum

The operculum is a smooth and featherless patch of skin located where the beak attaches to the forehead of certain birds. It is often enlarged and brightly colored such as one can observe in pigeons, parrots and birds of prey. It is also called the cere.

Outer primaries

The outer primaries are the primary feathers on the wing farthest from the body. They often appear to be the longest feathers on the wing.

Outer secondaries

The outer secondaries are the secondary feathers of the wing furthest away from the body.

Outer tail feathers

The outer tail feathers are the tail feathers farthest from the center. Many birds can “fan out” their tail and the outer tail feathers are those slightly shorter feathers that fan out the furthest.

Outer wing

The outer wing encompasses the alula and the primary feathers.
Patagial mark
The patagial mark is the dark patch closer to the body than to the outer edge of the wing underside when it is spread. It is located at the top of the wing closest to the head.

Pelagic

The pelagic is a type of bird whose habitat are on the open ocean rather than in a coastal region or on inland bodies of water (lakes, rivers). An example of a pelagic bird is the blacklegged kittiwake

Pinnae

The Pinnae are elongated feathers projecting from the upper body area, generally the neck or head. In the Prairie Chicken for example, the males have longer pinnae than females and they erect them during courtship display.

Plumes

The plumes are large, conspicuous, showy feathers that are not a good survival adaptation from the predator-prey point of view because they make the bird much more visible. However, plumes signal health and virility to a potential mate. As such males have more elaborate plumes than females.

Primaries

The primaries are the flight feathers specialized for flight. They are attached to the "hand" equivalent part of the wing.

Primary coverts

The primary coverts are shorter feathers that cover and protect the primary flight feathers.

Primary numbering

The primary numbering is a system developed to assign numbers to each primary feather for easier identification.

Pupil

The pupil is the dark circular, hollow passage in the middle of the iris through which the light enters the eye and forms an image on the back of the eye.

Rectrices

The retrices are the backmost margin of the tail formed by conspicuous.

Remiges

See primaries and secondaries.

Rictal bristles

The rictal bristles are the short and stiff feathers near the bill.

Rictus

The rictus is the base of the bill where the mandibles join. See also gape and commissure.

Ruffs

The ruffs are a fringe of feather growth on the neck of the bird. They are also used to signal good health and virility to potential mates. Unhealthy birds will have less full and less conspicuous ruffs.

Rump

The rump is the area between the uppertail coverts and the back of the bird. It consists of shorter feathers of the same color as the body.

Scapulars

The scapulars are short feathers in the area where the bird’s back and the wings join. They are generally short, soft and the same color as the back.

Secondaries

The secondaries are flight feathers attached to the equivalent of the human elbow. They come behind the primaries in importance and location when viewed from the outermost edge of the wing.

Secondary coverts

The secondary coverts are the feathers that cover and protect the secondaries, and are attached to the “elbow”.

Shoulder

The shoulder refers to the relatively short feathers overlying the median secondary coverts on the top of the wing. They are located near the back and can be seen as the “first row” of feathers on the bird’s wing. They are also called marginal coverts and lesser secondary coverts.

Side

The side is the area between the belly, the wing and the back,. It is equivalent to the area between the human armpit and the hip bone.

Side of neck

The side of neck is the area between the foreneck and hindneck. In humans, it is the area under the ear

Spectacle

The spectacle refers to the combination of the eye ring and supraloral line.

Speculum

The speculum is the brightly colored area on the wing (secondaries of the wing) on several duck species.

Subterminal band

The subterminal band are the stripes on the tails of certain birds. The stripe is located just before the tip

Superciliary line

The superciliary line is the arch of feathers growing overtop the bony arch of each eye in the same approximate location as the human eye brow. It is also called supercilium or eyebrow.

Supercilium

The supercilium is used as a term to describe the arch of feathers growing overtop the bony arch of each eye in the same approximate location as the human eye brow. It is also called superciliary line or eyebrow.

Supraloral line

The supraloral line is the line above the lore. In many species, it is a brightly colored line between the eye and the bill.

Tail

The tail comprises of long feathers extending from the rear of the bird and is used for balance and as an asset to attract potential mates. Certain species have extremely elaborate tail feathers, such as peacocks, which serve no other purpose than to convey a positive message to a female during courtship.

Tail coverts

The tail coverts are the shorter tail feathers covering the bases of the long extending tail feathers.

Tail numbering

The tail numbering is a system developed to assign a number to each tail feather which can convey certain characteristics about certain species.

Tarsus

The tarsus is the part of the leg between the knee and the foot of the bird, equivalent homologous to the lower leg in humans..

Temporal canthus

The temporal canthus is the outer corner of the eye closest to the ear.

Terminal band

The terminal band refers to the bright stripe at the tip of the tail in a deviating color from the rest of the color scheme.

Tertiaries

The tertiaries are guill feathers that are attached to the basal joint of the wing of a bird. They are located next to the secondaries.

Throat

The throat is similar to the human throat and is located the front of the neck. It is often called jugulum, foreneck or throat patch. Internally, it contains the main food passage from the bird's bill to its stomach as well as air passages to the lungs.

Throat patch

The throat patch is similar to the human throat and is located the front of the neck. See also jugulum, foreneck or throat. Internally it contains the main food passage from the birds bill to its stomach as well as air passages to the lungs.

Tibia

The tibia is homologous to the human upper leg and comprises the part of the bird’s leg above the knee and below the body.

Toe

The toes aredigits attached to the feet just like human toes. Most birds have four toes. The first toe points backwards while the other three toes point forward. The second, third and fourth digits or toes are counted from the inside of the foot out and have 2, 3 and 4 phalanges respectively. Most birds do not have a fifth toe, except for some where it has evolved into a defensive sput, such as in the chicken

Trailing edge of wing

The trailing edge is the edge of the wing seen when the wing is stretched out in flight and viewing it from the rear end of the bird. It is the area where the edges of the feathers are located, while the area where the feathers are attached is termed the leading edge of the wing.

Underparts

The underparts are those that can be seen looking up at a bird during flight - the belly, undertail coverts, chest, flanks and foreneck.

Undertail coverts

The undertail coverts are feathers in a triangular area on the undersurface of a bird between its vent and the base of its tail feathers. One can tell whether a bird is adult or juvenile by looking at the undertail coverts: Adult females tend to have conspicuous dusky edging to most of the feathers. Whereas juvenile females tend to have nearly pure white undertail coverts. They are also called crissum.

Underwing

The underwing is the bottom side of the wing. When the bird is stationary, it is the side pressed against the body and when the bird is in flight, it is the side one can see standing on the ground looking up at the bird.

Upper mandible

The upper mandible is the upper part of the bill. Most birds cannot move their upper mandible, except for a few species which can move both mandibles independently, such as the parrot.

Upper mandibular tomia

This is the cutting edge of the upper mandible, similar to the human teeth when looking at the skull only.

Upperparts

The upperparts are those parts visible when viewing a bird from the top - the back, rump, hindneck, wings and crown.

Uppertail coverts

The uppertail coverts are the relatively shorter feathers covering the upperside of the base of the tail. They originate on the rump and partially cover the tail giving it a “layered” look.

Upperwing

The upperwing is the visible part of the wing when looking at the bird from a top view. It is the part of the wing exposed when the bird is stationary and has its wings pressed against its body.

Vent

Birds do not have two separate cavities for excrement and reproduction like humans do. In birds, there is one single entrance/exit that suits both functions called the vent, cloaca or anus.

Whisker

The whisker is the area below the eye and bill and parallel to the throat. It is generally brightly colored and located on the sides of the chin stretching downwards. It is also called mustache, malar stripe or malar streak.

Wing

The wing is the feathered appendage that allows a bird to fly. Strong flight muscles are attached to the wing such that the bird can lifts its own bodyweight.

Wing bars

The wing bars make the bird's wing look "striped". They are pale or white tips of the greater and median secondary coverts on the wings. From a distance, it can be viewed as a horizontally striped pattern making the wing look layered.

Wing coverts

See also primary and secondary coverts.

Wing lining

The wing lining is the relatively shorter and softer median, lesser and marginal coverts on the underwing.

Wing stripe

The wing stripe is a paler area at the base of the wing which is made up of pale or white tips on the flight feathers.

Wingpit

The wingpit is located between the body and the wing of the bird, homologous to the human armpit. The area formally comprises also the base of the underside of the wing, extending to the ventral wing lining. Muscles in the area are heavily involved in flight. It is also called axillary.

Wrist

The wrist refers to the base of the primaries in the bird’s wing. Although homologous in relative location to the human wrist, the bird wrist is not as flexible as the human wrist.
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