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.
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