Transgenes encoding exogenous proteins are stably integrated into embryonic stem cells and are present in the somatic tissue of transgenic or chimeric birds. The transgenes encode exogenous proteins and are expressed in any of endodermal, ectodermal, mesodermal, or extra embryonic tissue. Tissue specificity is provided by selecting the content of the transgene accordingly. Transgenic birds whose genome is comprised of trangene derived exogenous DNA express exogenous proteins with tissue specificity, and specifically express exogenous proteins in the tubular gland cells of the oviduct to concentrate exogenous proteins in egg white.