AERIE: A nest located on a cliff or high place, usually built by a raptor, a bird of prey.


AIR SAC: A series of thin-walled sacs, typically eight or nine (but ranging from six to fourteen, depending on the species) that in conjunction with the paired lungs comprise the bird's respiratory system.


ALAR BAR: A contrasting line (bar) of plumage beginning in the alar region of the wing (where the wing bends at the wrist and on the leading edge) and running from that point at an angle toward the bird's body, stopping where the back of the wing joins the body. The effect is a patch or line of feathers that differ from the color of the wing feathers around it, thus producing a visible bar on the top of the wing. Sometimes the bar runs from the Alula to the base of the wing on the front side (leading edge).


ALTERNATE PLUMAGE: *See "Breeding Plumage."


ALTITUDINAL MOVEMENTS (Vertical Migrations): A bird's regular seasonal vertical movement, often from the mountaintops in summer to lower regions or valleys during winter, with a return to higher elevations the following spring.


ALTRICIAL: Term for young birds that hatch in a helpless state, usually naked with eyes closed, and are totally dependent on the parents.


ALULA: A small group of feathers that protrude from the outermost joint of the wing. It has its own group of muscles and moves independently from the flight feathers. By adjusting the angle of the alula, the bird is able to regulate the air flow over the top of the wing, allowing it to alight or land at slower speeds without stalling.


ANHEDRAL: The downward curve of a bird's wings when in flight.


ARBOREAL: A tree-dwelling bird.


AURICULARS: Feathers along the sides of the ears, often called ear coverts or ear patches.


AVIAN: of, relating to, or derived from birds.


AVIARY: a large cage, building, structure or enclosure for keeping birds in, usually primarily consisting of netting or fencing, and large enough to allow the birds to fly freely. 


AXILLARIES: Rigid feathers along the underside of the wings where they connect to the body, corresponding to the underarm area in a human.


BASIC PLUMAGE:*See "Winter Plumage."


BREEDING PLUMAGE: Seasonal alterations in appearance to attract birds of the opposite sex. such as changes in color or the addition of ornamental ruffs. This is accomplished by a feather molt from the basic, or winter, plumage.


CERE: The fleshy area on top of the base of the upper bill that contains the nostrils. Present on the bills of some bird species, particularly among birds of prey.


CLUTCH: The total number of eggs laid during a single nesting period; some birds lay several clutches in a nesting season.


COLONIAL: The pattern of nesting close together with birds of the same species. Sometimes only a few nests packed close together constitute a colony, but some may hold hundreds of thousands of nesting pairs.


CONSPECIFIC: Birds that are members of the same species.


CONGENERS: Distinct bird species that are related to one another by being in the same genus.


COVERTS: A covering of feathers overlaying the upper and lower part of the wings, covering the bases of the flight feathers (wing coverts); also on top of the tail feathers (upper tail coverts and under tail coverts).


CRECHE: An aggregation of hatchlings of a nesting colony, living together while they are in a dependent state and fed and tended by the adult birds.


CREPUSCULAR: Birds that feed and are active during twilight hours.


CRISSUM: Feathers covering the base of the under tail, usually a different color from the rest of the underparts.

*Also called "under tail coverts."


CROP: Where food is stored in the esophagus for later digestion, or to be regurgitated and fed to hatchlings. Some birds, such as pigeons and doves, have a two-chambered crop that produces special milk to nourish their young.


CROWN: the top of the birds head between the forehead and the back of the head or occiput.


CULMEN: The top ridge of the upper mandible, darker on some birds than the side of the bill.


DABBLING: Method of surface feeding by a relatively short-necked short-legged duck. It tips up the tail and body, then dips its bill and neck into the water. These ducks are called dabblers.

*Also referred to as "Tipping-up."


DECURVED: Sloped downward, usually referring to the bill.


DIHEDRAL: Wings held in a shallow V while bird is in flight.


DISTAL BAND: A strip of color near the end of the tail, end of wing, or on the lower part of the leg.


DIURNAL: Birds that feed and are active during the day.


EAR COVERTS:*See "Auriculars." 


EAR PATCHES: *See "Auriculars."


ECLIPSE PLUMAGE: Dull-colored plumage, similar to that of the female, into which many male ducks briefly molt in summer.


EXTIRPATED: Exterminated or destroyed from a part of a species range.


EYE RING:*See "Orbital Ring."


FIELD MARKS: Plumage or anatomical features of a bird that help to distinguish it from other similar species.


FLASHMARK: Color or marking on plumage that is visible only when the bird is in flight.


FLEDGE: The act of a young bird (nestling) leaving the nest.


FLEDGLING: A young bird that has feathers and is old enough to have left the nest but is still dependent on adult birds for care and feeding. The stage of development that follows the "nestling" stage.


GONYS: A ridge on the lower mandible of a gull that causes the midline to appear angled. Sometimes shows a red patch during breeding season.


GORGET: A small iridescent patch on the throat of a hummingbird.


GULAR SAC: A large or small pouch in the upper throat that helps a bird regulate body temperature and sometimes holds undigested food. In a few species, such as the magnificent frigatebird, the pouch greatly expands for courtship displays.


HAWKING: The act of catching prey, usually insects, in flight. Generally done with the bill. Typical of flycatchers.


HERONRY (Rookery): The colonial nesting site for herons, egrets, and ibises.


HINDNECK: The bird's nape or back of the neck.


HUMERAL: The patch of feathers overlying the bone near the upper wing or shoulder area.


JIZZ: The abstract combination of a bird's posture, plumage pattern, shape, size, and behavior that identifies a bird's species instantly without further examination.


LAMELLAE: Miniature ridges inside the bill of a duck or water bird that resemble the teeth of a comb and serve as a strainer during feeding.


LARDER: A place where a shrike impales and stores its prey on sharp branches or wire.


LEK: A communal gathering place during breeding season where males of some species of birds display to attract the females. It contains numerous territories, each guarded by a different male.


LORES: Space between the eyes and the base of the upper part of the bill on the side of the bird's face.


LOWER MANDIBLE:*See "Mandible."


MALAR: Refers to the cheek area along the side of the face. Field mark here is called "malar mark" or malar stripe."


MANDIBLE: The lower half of a bird's bill or beak.

*also referred to as the "lower mandible."


MANTLE: The feathers covering the back and upper wing coverts; feathers of the back and folded wings.


MANUS: The portion of a bird's wing that corresponds to the hand of a human. The fused bones of the palm and reduced digits bear the primary feathers and the alula.


MAXILLA: The upper half of a bird's bill or beak.

*also referred to as the "upper mandible."


MELANISTIC: A bird that has a surplus of dark pigment in its plumage.


MIMIC THRUSH: A member of the family Mimidae, which includes thrashers, catbirds, and mockingbirds.


MORPH: When birds of the same species have two or more different colored plumages, that are independent of season, sex, age, or breeding. Color phases may or may not be related to range and climate. An example would be the eastern screech owl which comes in three morphs... A red morph, grey morph, and brown morph.


NEOTROPICAL: The New World tropical region that encompasses the northern portion of the Mexican rain forest and the Caribbean islands, and extends to the nontropical regions of South America.


NEW WORLD: Earth's Western Hemisphere; includes North, South, and Central America.


NOCTURNAL: Birds that feed and are active at night.


NON-PASSERINE: Any of the birds that are not Passcrines, which are the songbirds or perching birds. Includes loons, waterfowl, owls, shorebirds, hawks, woodpeckers, and doves.


NUCHAL PATCH: A patch of contrasting color located on the back of the bird's neck or nape.


OCCIPITAL PATCH: A patch of color located high on the back of the head. Higher on the head than the nuchal patch.


OCCIPUT: The area on the back of a bird's head between the nape and the crown.


OLD WORLD: Earth's Eastern Hemisphere: Europe, Asia, and Africa.


ORBITAL RING: A circle around the eye, usually of a contrasting color.

*Also referred to as "Eye Ring."


PALEARCTIC: Faunal region surrounded by the Atlantic, Artic, and Pacific Oceans; encompasses Asia north of the Himalayas, Europe, and Africa north of the Sahara desert.


PASSERIFORM:*See "Passerines."


PASSERINES: Any of the birds belonging to the order Passeriformes, which comprise more than fifty percent of the world's birds. Highly evolved, these birds are able to sing and have three forward-pointing toes adapted for perching.


PEEP: A "Birder's" name for a group of small, similar-looking sandpipers; may have been derived from their high-pitched calls.


PELAGIC: Birds that spend most of their time at sea and rarely are seen from shore.


PIEBALD: Plumage that shows two contrasting colors.


POLYANDROUS: A female bird that has two or more mates; female often larger, has brighter plumage, and defends her territory. The male of the species usually incubates and tends young.


POLYGYNOUS: A male bird that has two or more mates.


POLYGAMOUS: When both male and female of a species may take two or more mates.


POSTOCULAR STRIPE: A line that leads from behind the bird's eye to the auricular or eye patch.


PRECOCIAL: Young birds that hatch with their eyes open, are down-covered, and are able to leave the nest within two days of hatching. These hatchlings may be either partially or not at all dependent on the parents for care and feeding.


PRIMARIES: One of two sets of flight feathers, or remiges, located distally to the secondaries and joined to the manus of the wing.


PROMISCUOUS: Birds, male or female, that come together solely for mating purposes and leave within a few hours to mate with other birds.


PYRIFORM: Pear-shaped; often used to describe shape of egg.


RAPTORS: A bird of prey such as hawks, falcons, eagles, kites, and owls.


RECTRICES: The principal feathers that make up the tail. They range in number from eight to twenty-four, with the average in songbirds being twelve.


REMIGES: Refers to flight feathers - primaries, secondaries, and tertials.


RIPARIAN: Located on or near a river bank, stream bank, or other body of water.


SCAPULARS: Feathers joined to the shoulder area of the bird and covering the top of the folded wing.


SECONDARIES: One of two sets of flight feathers located between the body and the primaries and joined to the part of the wing that corresponds to the forearm of a human.


SEMIALTRICIAL: Young birds that hatch with their eyes either open or closed, are down-covered, and are incapable of leaving the nest; fed by parents.


SEMICOLONIAL: Nesting pattern in which several birds of the same species nest close to one another, often within sight of each other's nests and do not behave aggressively toward one another.


SEMIPRECOCIAL: Young birds that hatch with their eyes open, are down-covered, and able to leave the nest soon after hatching, but remain in nest and are fed by parents.


SHANK:*See "Tarsus."


SKYLARKING: Elaborate territorial display flight given by a male songbird. It sings and often flutters in circles before swooping back to earth.


SPATULATE: A long rounded apoonlike shape; sometimes used to describe a bill or tail.


SPECULUM: A small area of contrasting iridescent feathers located on the secondary feathers of the wings. Often seen in ducks.


SUPERCILIARY STRIPE:*See "Supercilium."


SUPERCILIUM: Line above each eye; an eyebrow.

* Also referred to as a "Superciliary Stripe."


SUPERSPECIES: Closely related species that are often separated from each other by geographic barriers. Without these barriers the two species probably would interbreed and become one.


SYMPATRIC: Birds that inhabit the same range but remain distinct and separate species.


TARSUS: The top of the foot behind the toes, often called the shank. Usually either bare or covered with scales, plates, or sometimes feathers.


TERTIALS: The group of secondary feathers that are closest to the body; often a contrasting color.


TIPPING-UP: Method of surface feeding by a duck, goose, or swan in which it raises its tail and dips its bill, head , and neck into the water.
*Also referred to as "Dabbling."


TOTIPALMATE: A bird that has all four toes joined together by webbing.


TYMPANI (Tympaniform membranes): Valves in the voacal organ of a bird that produces sound.


UNDERPARTS: The plumage and coloring on a bird's breast, belly, sides, flanks, and undertail coverts.


UPPER MANDIBLE:*See "Maxilla."


UPPERPARTS: The plumage and coloring on a bird's nape, back, shoulders, rump, and upper part of tail.


VANE: Contoured flight feather that acts as a propeller. It consists of a central shaft surrounded by an inner and outer web.


VENT: The opening of the cloaca, or anus; sometimes refers to a contrasting patch of feathers in this area.


WATTLE: Fleshy piece of brightly colored skin that hangs from the lower bill; associated with turkeys and some chickens.


WILDTYPE: A biological term based in genetics that describes the form that most individuals in a wild population take; description includes shape, color, patterns, and size.


WINGSTRIPE: A distinct line on the wing, usually of a contrasting color.


WINTER PLUMAGE (Basic plumage): Seasonal alteration in a bird's appearance produced by the fall molt.