What Is the Migratory Bird Treaty Act?

The Migratory Bird Treaty Act, or MBTA, is a U.S. law protecting a wide variety of native birds from human activities. Passed in 1918, the MBTA is one of the first U.S. laws to protect wildlife. Since then, various interpretations of the MBTA have periodically expanded and reduced both the number of birds protected under the law and the significance of the law's protections. Most recently, the MBTA's breadth of protections was reduced to only include the intentional harm of birds—people who unintentionally hurt or kill birds protected under the MBTA are no longer subject to consequences under the Act.

Origin and Background

In the 1800s, U.S. bird populations plummeted due to combined demands for birds and their eggs as food and the use of their feathers in women's hats. In the western United States, a lack of domesticated chickens led people to steal eggs from seabird colonies to meet the demands of California's booming Gold Rush population. All over the United States, the desire for feathered hats in the late 19th century and early 20th century killed millions of birds every year. As a result of human activities, many bird species went extinct.

Creation of the Audubon Society

Outraged by the loss of birds, socialites Harriet Hemenway and Minna B. Hall founded the first Audubon Society in Massachusetts in 1896. In the following two years, Audubon Societies were established in 14 more states and the District of Columbia.

In 1900, the Audubon Society held its first "Christmas Bird Count"—an annual bird census conducted entirely by volunteers. The Christmas Bird Count, or CBC, remains a holiday tradition in the U.S. today and has resulted in data instrumental in the protection of birds.

The Audubon Society's Legislative Victories

In the early 1900s, the Audubon Society achieved a series of state and regional successes in their pursuit to protect U.S. birds. In 1903, the Florida Audubon Society successfully convinced President Theodore Roosevelt to establish the first national bird sanctuary: the Pelican Island and Indian River Lagoon. The Pelican Island bird sanctuary quickly gave rise to the National Wildlife Refuge System, which established protections for birds at a number of key locations.

A decade later, a new federal law extended protections to U.S. birds beyond a few key habitats. Instead, the 1913 Weeks-McLean Law established protections for the birds themselves. The law prohibited people from hunting migratory birds during the spring when most birds nest and raise their young. The Weeks-McLean law also prohibited the import of wild bird feathers for use in women's fashion. In 1918, the Weeks-McLean Act was replaced by the Migratory Bird Treaty Act of 1918.

The Migratory Bird Treaty Act

The Migratory Bird Treaty Act of 1918 established protections for birds that migrate across the U.S.-Canada boarder through an international treaty. In subsequent amendments to the MBTA, the United States entered into additional treaties with Mexico, Japan, and Russia. Each of these four treaties protect birds that migrate between countries.

The MBTA prohibits the "take" of any migratory birds that cross international borders without prior authorization from the U.S. Fish and Wildlife Service (USFWS).

If a person or organization's actions could result in the "take" of a protected migratory bird, a permit from the USFWS must be obtained beforehand. Today, the "take" of a birds protected under the MBTA without USFWS approval is considered a misdemeanor under U.S. law and carries a penalty of up to six months in prison and a $15,000 fine.

Revisions to the Migratory Bird Treaty Act

Since the law's implementation in 1918, the MBTA has been both amended and subject to differences in interpretation.

1936: Treaty Between the U.S. and Mexico

In 1936, the Convention for the Protection of Migratory Birds and Game Mammals expanded MBTA protections to include birds that migrate between the U.S. and Mexico. Authorization from both countries is needed to transport birds, feathers, or bones protected by the MBTA across the U.S.-Mexico border.

1940: Bald Eagle Protection Act

Both the bald eagle and golden eagle have non-migratory populations in the United States, leaving these two bird species without clear protection under the Migratory Bird Treaty Act. While the Lacey Act of 1900 already provided some protections for bald eagles, additional protections for the symbolic bird were added to the MBTA through the 1940 Bald Eagle Protection Act. Protections for the golden eagle were subsequently added to the Bald Eagle Protection Act though an amendment in 1962.

1972: Protections for Eagles and Hawks

The 1972 amendment to the MBTA further extended the federal law's protections to include an additional 32 bird families, including all eagles, hawks, owls, and corvids. Like the 1940 Bald Eagle Protection Act, this 1972 amendment expanded the MBTA's protections beyond just birds that migrate across U.S. borders.

The Migratory Bird Treaty Act Today

Today, MBTA protects nearly all U.S. birds—not just migratory species. However, the extent of the MBTA's protections continues to be contested. While the Migratory Bird Treaty Act considers "take" to mean to "pursue, hunt, shoot, wound, kill, trap, capture, or collect," the definition of "take" under the Endangered Species Act (ESA) is more broad. Under the Endangered Species Act, "take" also includes actions that unintentionally harm protected birds—a type of take known as "incidental take".

At times, the U.S. Fish and Wildlife Service—the agency responsible for implementing both the MBTA and the ESA—has applied the ESA's definition of incidental take to all birds protected under the MBTA. The agency's broad interpretation of "take" under the MBTA has been contested in courts with varying results.

In 2017, the Trump Administration issued a new interpretation of the MBTA which loosened the law's protections. Under the new interpretation, human activities that accidentally affect protected birds no longer require a federal permit from the U.S. Fish and Wildlife Service. In other words, only actions that intentionally hurt or kill birds protected under the MBTA need a permission from the U.S. Fish and Wildlife Service. Without incidental take protections, critics of the Trump Administration's decision say it removes major incentives to protect birds—why would a company take extra steps to reduce the risk of killing birds if it's not required?

The 2017 interpretation of the MBTA remained controversial and ambiguous for years following the rule's publication until the rule was finalized in January 2021. However, the U.S. Fish and Wildlife Service proposed to revoke the Trump Administration's interpretation in May 2021. The 2017 interpretation of the MBTA remains in effect today.