According to this invention, a bird lays an egg that does not contain an artificially introduced foreign gene in genome thereof and has an ovomucoid content lower than that in a wild type thereof. A method for producing a bird includes a modification step of cleaving the ovomucoid gene locus in a pluripotent stem cell of a bird with programmable endonuclease so as to modify the ovomucoid gene locus and a transplantation step of transplanting the pluripotent stem cell in which the ovomucoid gene locus is modified into an embryo of a bird. A bird egg does not contain an artificially introduced foreign gene in genome thereof and has an ovomucoid content lower than that in a wild type thereof.
