Glossary of Avian External Anatomy

Prepared by Dennis Paulson

This list of mostly technical terms is provided as a service to those not familiar with them. Many of them are in general use in anatomy, others restricted to birds. If any obvious ones are missing, I would appreciate a note to that effect.

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Internal anatomy of a bird: a warm-blooded animal with two wings, two feet, a horny beak and a body covered with feathers.
Spinal column: part of the nervous system with the spinal column.
Lung: saclike respiratory organ.
Kidney: blood-purifying organ.
Ureter: duct that carries urine from the kidney to outside the body of a bird.
Cecum: cul-de-sac of the intestine.
Rectum: last part of the intestine.
Intestine: last part of the digestive tract.
Gizzard: last pocket of the stomach of a bird.
Liver: bile-producing digestive gland.
Heart: blood-pumping organ.
Crop: pocket formed by the building of the esophagus.
Esophagus: first part of the digestive tract.
Trachea: first part of the respiratory system.
Buccal cavity: chamber of the mouth.

Homeostasis: Keeping the internal conditions fixed (within the normal range) whatever changes happen in the external conditions. **

Acuminate: abruptly narrowing to sharp point

Acute: sharply pointed

Alula: a small winglike group of feathers at the bend of the wing, supported by the anterior most digits

Angulated: with an angle

Anisodactyl: three toes in front and one behind, as in perching birds

Anteriad: toward the front

Apteria: plural of apterium

Apterium: unfeathered area between feather tracts

Auditory meatus: ear opening

Beak: the bill

Bipedal: standing on two rather than four legs

Booted: not divided into scales (tarsus)

Caeca: plural of caecum

Caecum: a diverticulum on each side of the gut at junction of small and large intestines, for additional digestion

Caudad: tailward (toward the rear)

Cere: fleshy area at bill base enclosing nostrils

Cloaca: common chamber at end of digestive and urogenital systems

Commissure: line formed by meeting of maxilla and mandible

Compressed: flattened from side to side

Cornified: with a keratinous (horny) covering

Coverts: smaller feathers covering large wing and tail feathers

Culmen: upper ridge of maxilla

Decurved: curved downward toward tip

Depressed: flattened from top to bottom

Elevated: above front toes (hallux)

Emarginate: notched (tail)

Filamentous: very long and slender

Filoplumes: hairlike feathers

Gonys: lower edge of mandible

Graduated: feathers successively shorter from center to outside (tail)

Gular sac: bare skin on throat and base of mandible

Hallux: hind toe

Imperforate: separated by a septum (nostrils)

Incumbent: at level of other toes (hallux)

Lamellate: coarse or fine parallel ridges or plates (at cutting edge of bill)

Lobate: with lobes (toes)

Lore: area between eye and bill

Mandible: lower bill

Maxilla: upper bill

Nares (sing., naris): nostrils

Nictitating membrane: "third eyelid" drawn over the eye to clean it

Notched: with a notch, like a pointed bite taken out of it (bill, tail)

Obtuse: not very sharply pointed

Operculum: fleshy partial covering over nostril

Palmate: completely webbed (3 toes connected)

Pamprodactyl: all four toes in front, as in swifts

Pectinate: comblike (structure on one side of central toenail)

Perforate: continuous with other side (nostrils)

Posteriad: toward the rear

Primaries: 9-10 or more outermost flight feathers, attached to hand

Pteryla: feather tract

Pterylae: plural of pteryla

Raptorial: feet with long, strong toes and long, sharp, curved claws

Rectrices: plural of rectrix

Rectrix: tail feather

Recurved: curved upward toward tip

Remex: large flight feather

Remiges: plural of remex

Reticulate: with small netlike scales (tarsus)

Rhamphotheca: horny covering of bill

Rictal: referring to the corners of the mouth

Scutellate: with large transversely oriented scales (tarsus)

Secondaries: flight feathers attached to forearm (ulna)

Semipalmate: webbed only at base (toes)

Serrate: with teeth like saw (cutting edge of bill)

Spatulate: spoon-shaped (bill)

Sternum: the large bone underlying the breast

Syndactyl: two front toes partially joined, as in kingfishers

Tarsi: plural of tarsus

Tarsometatarsus: the bone underlying the tarsus

Tarsus: lowest segment of leg, before toes

Terete: round in cross section

Tertials: flight feathers attached to upper arm (humerus)

Tibia: segment of leg that protrudes from feathers, above "ankle"

Tomium: cutting edge of both maxilla and mandible

Totipalmate: all 4 toes connected by web

Uropygial gland: papilla on top of uropygium that secretes oils for preening

Uropygium: the fleshy posterior end supporting the tail

Vent: opening of cloaca

Zygodactyl: two toes in front and two behind, as in woodpeckers