An aim is to produce a suitable foreign protein in egg white in transgenic birds at levels equivalent to or higher than the expression levels achieved using an ovalbumin promoter or an actin promoter, and to reduce the great burden on birds by reducing the expression at sites other than the oviduct while achieving expression sufficient to predict the expression levels before the birds reach sexual maturity. Provided is a transgenic bird containing a nucleic acid base sequence in chromosome in a cell that forms the oviduct, the sequence containing: (a) an avian endoplasmic reticulum chaperone promoter and (b) a nucleic acid base sequence encoding a suitable foreign protein, functionally linked to the promoter. Also provided is a method for producing a suitable foreign protein, including recovering the suitable foreign protein from the transgenic bird. Further provided is a method for producing a transgenic bird, including introducing a nucleic acid base sequence into a chromosome in a cell that forms the oviduct, the sequence containing: (a) an avian endoplasmic reticulum chaperone promoter and (b) a nucleic acid base sequence encoding a suitable foreign protein, functionally linked to the promoter.
