鸟类
鸟纲

[ noun ]
(ornithology) the class of birds
<noun.animal>

Aves \A"ves\, n. pl. [L., pl. of avis bird.] (Zo["o]l.)
The class of Vertebrata that includes the birds.

Note: Aves, or birds, have a complete double circulation,
oviparous, reproduction, front limbs peculiarly
modified as wings; and they bear feathers. All existing
birds have a horny beak, without teeth; but some
Mesozoic fossil birds (Odontornithes) had conical teeth
inserted in both jaws. The principal groups are:
{Carinat[ae]}, including all existing flying birds;
{Ratit[ae]}, including the ostrich and allies, the
apteryx, and the extinct moas; {Odontornithes}, or
fossil birds with teeth.

Note: The ordinary birds are classified largely by the
structure of the beak and feet, which are in direct
relation to their habits. See {Beak}, {Bird},
{Odontonithes}.
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