The Migratory Bird Treaty Act (MBTA), enacted in 1918 and one of the oldest U.S. environmental laws, prohibits the unauthorized killing of migratory birds. 16 U.S.C. §§703-712. The MBTA was first enacted to codify a treaty between the United States and Canada (then part of Great Britain) in response to the extinction or near extinction of birds, many of which were hunted for their feathers. The broadly-worded statute says in relevant part that “it shall be unlawful at any time, by any means or in any manner, to pursue, hunt, take, capture, kill … any migratory bird … .” Id. §703(a). MBTA violations are criminal offenses, with misdemeanor convictions up to $15,000 and/or six months of jail per violation. 16 U.S.C. §707(a). Courts apply a strict liability standard to misdemeanor MBTA violations, so the government need not prove a defendant’s intent to kill; intentional violations are felonies.

The issue that has been subject to disagreements among federal courts and within the Interior Department is whether the MBTA prohibits an “incidental take,” which is killing birds through an activity whose purpose is not killing birds. Incidental takes include deaths from power lines, wind turbines, and buildings, and poisoning from commercial or industrial activity such as from uncovered waste ponds.