Linnean classification was not available in the time of the writing of Leviticus and Deuteronomy, and the scientific definition of what a 'bird' was did not exist either. Classification of animals and things was made by different means: function or form. In this case, the word rendered birds means simply 'owner of a wing', the word being 'owph, which comes from a root word which means to cover or to fly.

The category of 'owph includes birds, bats, and certain insects. Even modern ecologists classify water-dwelling life in a very similar way according to their mode of living: plankton (floaters/drifters), nekton (swimmers) and benthos (bottom-dwellers). It is unreasonable to propose that when the Hebrews used this word, they had in mind the modern classification scheme which defines 'bird' as a warm-blooded creature of a certain class who had feathers.