1918: Migratory Bird Treaty Act (MBTA)
In 1916, the United States and Great Britain (on behalf of Canada) adopted a uniform system of protection for certain species of birds which migrate between the United States and Canada. On July 3, 1918, the United States passed the Migratory Bird Treaty Act to implement the earlier treaty. Click here for the Act's language from the updated U.S. Code.
This act provided important protections to many birds, including the spotted owl, even before the passage of the Endangered Species Act in 1973.