All birds or animals, or parts thereof, captured, injured, or killed, and all grass and other natural growths, and nests and eggs of birds removed contrary to the provisions of sections
690 to
690i of this title or any regulation made pursuant thereto, shall, when found by such employee or by any marshal or deputy marshal, be summarily seized by him, and upon conviction of the offender or upon judgment of a court of the United States that the same were captured, killed, taken, or removed contrary to the provisions of sections
690 to
690i of this title or of any regulation made pursuant thereto, shall be forfeited to the United States and disposed of as directed by the Secretary of the Interior, in accordance with law.