Birds may be defined oviparous vertebrated animals, organized for flight.
In the Mosaic law, birds were distinguished as clean and unclean: the first being allowed for the table, because they fed on grain, seeds, and vegetables; and the second forbidden, because they subsisted on flesh and carrion. The birds most anciently used in sacrifice were, it seems, turtle-doves and pigeons. In Kitto's Physical History of Palestine there is a more complete notice than exists elsewhere of the actual ornithology of the Holy Land.