Avian Terminology
Air sacs
Thin membrane of the avian respiratory system that allows unidirectional flow of air into the
lungs and through the body. There are a total of 9 air sacs, 4 paired (2 cervical sacs, 2 anterior
thoracic sacs, 2 posterior thoracic sacs, 2 abdominal sacs) and 1 unpaired (interclavicular).
Anisodactyl
The most-common anatomical make-up of a birds foot, in which three toes point forward and
one toe (hallux, or fist toe) points backwards, a characteristic of passerines.
Apteria
The featherless tracts on a bird. There are several, but the most useful is the apteric tract that
exposes the jugular vein for venipuncture.
Blood feather
A new feather that is growing has a venous and arterial blood supply. This gives the feather a
thickened, purple appearance. As the feather matures, the blood supply recedes.
Choana
A slit in the roof of a bird’s mouth (in the upper mandible). The choana connects the oropharynx
inside the mouth with the nasal cavity. Numerous projections or papillae are found at the edge
of the choana.
Choanal papillae
Several tiny projections that line the choanal slit. These papillae should be sharp, and blunting
or absence is often attributed to nutritional deficiencies and/or respiratory illness.
Cloaca
The common posterior cavity into which the gastro-intestinal, urinary and genital tracts meet. All
birds have this structure from which they excrete urine, feces eggs. Comes from the Latin word
meaning “sewer”.
Dimorphism
The physical characteristics differentiate male from female species.
Feather
A keratinous structure covering the body of a bird. The central shaft is called the rachis. From
this, multiple barbs and barbules emerge forming the feather. The feathers are lightweight and
strong providing the bird with a protective covering as well as a mechanism for flight. Down
feathers provide the bird with insulation and protect the skin from getting wet.
Fledgling
A baby bird that has left it’s nest but is not yet able to fly, or feed itself without assistance from
it’s parents.
Heterodactyl
The unique anatomical make-up of a bird’s foot where digits 3 and 4 face forward, digits 1 and 2
face backward.
Lobate
The anatomy of bird’s foot where each toe (2, 3 4) are edged with separate webbing. An
example of this is seen in the American coot.
Palmate
The anatomical make-up of a bird’s foot where the front toes are connected by webbing. The
most common type of webbed foot and is seen in ducks, geese, swans, gulls, turns and other
aquatic species.
Pamprodacytl
The unique anatomical make-up of a bird’s foot where all four digits face forward, characteristic
of swifts.
Pneumatic bone
Flighted birds have evolved some bones that are hollow and allow the bird to be light enough
for flight. The pelvic bones, some ribs, the humerus, and femur all have large air filled medullary
canals that are involved with the respiratory cycle during flight.
Polyostotic Hyperostosis
Radiographic evidence suggestive of hyperestrogenism that appears as calcification of the
medullary spaces of the long bones, particularly of the femur and tibia.
Pterylae
The feather tracts on the skin of the bird from which the feathers grow.
Semipalmate
The anatomical make-up of a bird’s foot where the anterior toes are joined part way by a small
webbing. May also be referred to as “half-webbed”.
Syndactyl
The anatomical make-up of a bird’s foot where the two front toes (second and third digits) are
partially joined or webbed for much of their length. Common in kingfishers and hornbills.
Syrinx
The vocal organ of birds, located at the base of the trachea where it bifurcates into the bronchi.
Not seen in all avian species.
Totipalmate
The anatomical make-up of a bird’s foot where all four toes are connected by a thin web. Seen
in birds such as the cormorant and pelican.
Uropygial gland
Also known as the “preen gland.” It is a gland found on the dorsal aspect at the base of the tail,
which secretes an oil used for preening. Not all species of birds will have a uropygial gland,
such as the Amazon parrot.
Weaning
The process of a baby bird learning to eat solid/adult food and no longer being dependant on
the parents for regurgitated food.
Wing trimming
The process of cutting the primary flight feathers to temporarily take away a bird’s ability to fly.
Zoonosis
An infectious disease that is able to be transmitted from humans to animals, or from animals to
humans.
Zygodactyl
The second most common anatomical make-up of a bird’s foot, where the toes are arranged in
pairs to help with grasping. The zygodactyl foot has two toes facing forwards (digits 2 3) and
two toes facing backward (digits 1 or hallux, 4). Zygodactyl anatomy is found in the osprey,
most woodpeckers, owls, cuckoos and parrots.