The Secretary of the Interior may- (1) purchase or rent such areas or interests therein as have been approved for purchase or rental by the Commission at the price or prices fixed by the Commission; and (2) acquire, by gift or devise, any area or interests therein; which he determines to be suitable for use as an inviolate sanctuary, or for any other management purpose, for migratory birds. The Secretary may pay, when deemed necessary by him and from moneys authorized to be appropriated for the purposes