Mishnà su Levitico 5:3

Thirteen rulings govern the carrion of a clean bird:There must be intention; It need not be rendered susceptible; It conveys food uncleanness if its minimum bulk is that of an egg; And it conveys uncleanness when in one's gullet if its minimum bulk is that of an olive; He that eats of it must wait until sunset [to be clean]; Guilt is incurred on account of it for entering the sanctuary; Terumah is burned on account of it; He who eats a limb of it while it is alive suffers forty lashes; Slaughtering it or nipping [off its neck] cleanses it even if it is terefah, the words of Rabbi Meir. Rabbi Judah says: they do not cleanse it. Rabbi Yose says: the slaughtering does cleanse it but nipping does not.