No person shall import migratory game birds killed in any foreign country, except Canada, unless such birds are dressed (except as required in §20.63), drawn, and the head and feet are removed: Provided, That this shall not prohibit the importation of legally taken, fully feathered migratory game birds consigned for mounting purposes to a taxidermist who holds a current taxidermist permit issued to him pursuant to §21.24 of this chapter and who is also licensed by the U.S. Department of Agriculture to decontaminate such birds.