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 § 21.63 of this chapter and who is also licensed by the U.S. Department of Agriculture to decontaminate such birds.