Whenever the Secretary shall find that emergency State action to prevent forest fires in any extensive area has resulted in the shortening of the season during which the hunting of any species of migratory game bird is permitted and that compensatory extension or reopening the hunting season for such birds will not result in a diminution of the abundance of birds to any greater extent than that contemplated for the original hunting season, the hunting season for the birds so affected may, subject to all other provisions of this subchapter, be extended or reopened by the Secretary upon request of the chief officer of the agency of the State exercising administration over wildlife resources. The length of the extended or reopened season in no event shall exceed the number of days during which hunting has been so prohibited. The extended or reopened season will be publicly announced.