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The U.S. Fish and Wildlife Service (USFWS) published a final rule that becomes effective on February 8, 2021, reaffirming a solicitor’s opinion that the Migratory Bird Treaty Act (MBTA) applies only to actions directed at migratory birds, their nests, or their eggs. The new regulation states that “injury to or mortality of migratory birds that results from, but it not the purpose of, an action (i.e., incidental taking or killing) is not prohibited by the Migratory Bird Treaty Act.”



The MBTA protects more than 1,000 bird species from acts that include, among other things, pursuing, hunting, taking, capturing, and killing at any time, by any means, or in any manner, unless permitted by regulation.

Until 2017, the USFWS had long interpreted the MBTA to prohibit the taking or killing of migratory birds that occurs incidental to other activities. Violations of the MBTA are criminal offences, but the USFWS does not have a regulatory program for addressing this kind of impact. Instead, the agency relied on its prosecutorial discretion to enforce the MBTA and generally prioritized circumstances when a violation was direct and foreseeable or was the outcome of “extrahazardous” activity. 

Prosecutions under the MBTA for incidental takings and killings have resulted in multi-million-dollar fines and imprisonment. However, legal interpretations varied by geography because various Federal Courts of Appeals had issued differing opinions.

These circumstances created considerable confusion and uncertainty within the regulated community about when the prohibitions of the MBTA apply and how to remain in compliance.



The new regulation clarifies, as a matter of law and policy, that incidental taking or killing of migratory birds is not prohibited by the MBTA. For example: 

  • Migratory bird deaths resulting from collisions with wind turbines, transmission lines, windows, or vehicles are not prohibited 
  • Migratory bird deaths resulting from contact with hazardous materials stored in waste pits are not prohibited

Please note that relevant state and local regulations still apply.



The new regulation is highly controversial. The upcoming change in Administration and a new Congress create a possibility that within the next two months Congress could repeal this regulation pursuant to the Congressional Review Act.

  • If repealed, it is likely that the USFWS will revert to its prior interpretation of the MBTA and practice of prosecutorial discretion regarding enforcement, subject to the applicable court precedent.
  • If not repealed, then legal challenges from environmental groups and others are certain to be filed. Such cases may take years to resolve.

In the meantime, the USFWS will continue to offer technical assistance and guidance to those seeking to reduce impacts on migratory birds, such as best practices or technologies that avoid or minimize incidental take of migratory birds. 



SWCA can answer questions and help you understand what this new MBTA regulation means for your activities.  Contact your SWCA project manager or our migratory bird experts for more information:

  • pkroberts [at] swca [dot] com (Pauline Roberts)
  • dwfaulkner [at] swca [dot] com (Doug Faulkner)
  • psunby [at] swca [dot] com (Paul Sunby)