The Migratory Bird Treaty Act of 1918 is one of the oldest federal wildlife protection laws in the United States, and it remains one of the most far-reaching. Born out of a conservation agreement between the United States and Great Britain on behalf of Canada, the law makes it illegal to kill, capture, sell, or possess migratory birds, their nests, or their eggs without federal authorization.1The Journal of Wildlife Management. The migratory bird treaty and a century of waterfowl conservation Over the past century, the Act has expanded to cover more than a thousand species and has become the backbone of bird conservation policy in North America, though its enforcement and scope have generated persistent legal and political controversy.
Why the Law Exists
By the late 1800s, North American bird populations were in steep decline. Market hunting drove much of the damage: millions of birds were killed annually for food, feathers, and sport with essentially no legal limits. Species like the passenger pigeon, once numbering in the billions, had been hunted to functional extinction. Shorebirds, waterfowl, and songbirds were all under enormous pressure. The millinery trade alone consumed vast quantities of egrets, herons, and terns, whose plumes adorned fashionable hats.
Early attempts at federal regulation ran into constitutional problems. The Weeks-McLean Act of 1913 tried to place migratory birds under federal jurisdiction, but courts questioned whether Congress had the authority to regulate wildlife that had traditionally been managed by states. Conservationists and federal officials realized that a treaty with another nation would provide stronger constitutional footing, because the Constitution grants the federal government broad power to implement treaties. That insight led to the 1916 Convention between the United States and Great Britain, acting on behalf of Canada, which committed both countries to protecting shared migratory bird populations.1The Journal of Wildlife Management. The migratory bird treaty and a century of waterfowl conservation Congress passed the Migratory Bird Treaty Act in 1918 to implement that convention domestically.
The treaty approach worked. In 1920, the Supreme Court upheld the Act in Missouri v. Holland, ruling that the federal government’s treaty power authorized it to regulate migratory birds even though states had historically managed wildlife. That decision settled the constitutional question and gave the MBTA a legal foundation that has held for over a century.
Expanding Beyond Canada
The original 1916 convention covered only birds migrating between the United States and Canada. But migratory birds do not respect political boundaries drawn on a map, and it quickly became clear that bilateral protection was not enough. The United States subsequently signed similar treaties with Mexico in 1936, Japan in 1972, and the Soviet Union (now Russia) in 1976. Each new treaty brought additional species under the Act’s umbrella and extended cooperative conservation obligations across wider geographic ranges.
The treaty with Mexico was particularly significant because many North American songbirds and raptors winter in Mexico and Central America. Protecting breeding habitat in the United States and Canada accomplished little if the birds were being killed in large numbers on their wintering grounds. The Japanese and Soviet treaties added protections for seabirds, shorebirds, and species that migrate across the Pacific, bringing the Act’s species list well beyond waterfowl and game birds.
Today, the official list of species protected under the MBTA includes over 1,100 bird species found in the United States. The U.S. Fish and Wildlife Service maintains and periodically updates this list. Nearly every native bird species you might encounter in the United States is covered, from bald eagles to common sparrows. Notably, a few groups are excluded: non-native species like house sparrows, European starlings, and rock pigeons are not protected, nor are most domestic poultry.
What the Act Actually Prohibits
The MBTA’s language is broad. Federal regulations implementing the Act state that no person may take, possess, import, export, transport, sell, purchase, barter, or offer for sale any migratory bird, or the parts, nests, or eggs of such a bird, except under a valid permit or other regulatory authorization.2eCFR (Electronic Code of Federal Regulations). Title 50 — Part 21: Migratory Bird Permits The word “take” in wildlife law covers killing, hunting, capturing, collecting, and disturbing. Even possessing a feather picked up off the ground technically falls under the statute, though enforcement at that level is extremely rare.
This breadth is deliberate. The Act was designed to shut down the commercial exploitation of wild birds entirely. You cannot legally sell a stuffed migratory bird, trade in their feathers, collect their eggs, or destroy an active nest without authorization. The prohibitions apply to everyone: individuals, businesses, and government agencies alike.
Penalties for violations range from misdemeanor charges for most offenses to felony charges when commercialization is involved. A standard misdemeanor violation can carry fines of up to $15,000 and six months in prison per offense. Felony violations, such as selling protected birds or their parts, can bring fines of up to $250,000 for individuals and two years of imprisonment. In practice, the heaviest penalties tend to fall on commercial operations and repeat offenders rather than on individual landowners or casual violators.
Permits and Exceptions
The MBTA is strict in its general prohibitions, but it includes a permitting system that allows certain activities under controlled conditions. The U.S. Fish and Wildlife Service issues permits for scientific research, educational use, falconry, taxidermy, depredation control, and regulated hunting, among other purposes.2eCFR (Electronic Code of Federal Regulations). Title 50 — Part 21: Migratory Bird Permits
Hunting is the most visible exception. Waterfowl and certain other game birds can be legally hunted during established seasons, under bag limits and other regulations set annually by the Fish and Wildlife Service in consultation with state agencies and flyway councils. These annual hunting frameworks are among the most data-intensive wildlife management processes in the world, drawing on population surveys, banding data, and harvest estimates to set seasons that aim to keep populations sustainable.1The Journal of Wildlife Management. The migratory bird treaty and a century of waterfowl conservation
Depredation orders provide another category of exception. When migratory birds cause damage to agriculture, property, or human health, the Fish and Wildlife Service can authorize their control. Standing depredation orders exist for certain species in certain situations, such as blackbirds damaging crops. Individual depredation permits can also be issued when a specific conflict arises. In Alaska, subsistence harvest regulations allow indigenous communities to take migratory birds and eggs during spring and summer, a practice with deep cultural roots that was formally incorporated into the regulatory framework in 1997.
Public, scientific, and educational institutions can also qualify for exceptions, and banding and marking programs operate under special permits that allow researchers to capture, band, and release birds for population studies.2eCFR (Electronic Code of Federal Regulations). Title 50 — Part 21: Migratory Bird Permits The data from these programs have been essential to understanding migration routes, survival rates, and population trends.
The Incidental Take Controversy
The single most contentious issue in MBTA enforcement over the past several decades has been whether the Act applies to “incidental take,” meaning bird deaths that are not the purpose of an activity but are a foreseeable side effect. Think of birds killed by colliding with communication towers, electrocuted on power lines, drowned in oil waste pits, or struck by vehicles. Nobody set out to kill these birds, but the activities that caused their deaths were predictable.
For much of the Act’s history, the Fish and Wildlife Service and federal courts treated incidental take as a potential violation. Companies that operated uncovered oil pits, for example, faced prosecution when migratory birds landed in toxic waste and died. This interpretation gave the agency leverage to push industries toward bird-safe practices: covering oil pits, retrofitting power lines, and designing buildings with bird-friendly glass.
The legal landscape shifted dramatically in 2017, when a Department of the Interior solicitor’s opinion concluded that the MBTA applies only to activities whose purpose is to take or kill migratory birds. Under this reading, incidental take was not a violation. The opinion effectively removed the Act as a tool for addressing the largest categories of human-caused bird mortality, since very few modern bird deaths result from intentional killing. Environmental groups and many wildlife biologists objected strenuously.
In 2021, the Biden administration reversed that interpretation, proposing to restore the Act’s applicability to incidental take and to create a general permit system that would allow industries to obtain coverage for foreseeable bird mortality in exchange for implementing best management practices. That rulemaking process has been politically fraught, with industry groups arguing that broad incidental take liability creates unworkable legal exposure and conservation groups countering that the Act is toothless without it. A 2024 commentary in the Proceedings of the National Academy of Sciences argued specifically that enforcing the MBTA against building collisions, one of the largest sources of anthropogenic bird death, should be a priority.3PubMed Central. To mitigate bird collisions, enforce the Migratory Bird Treaty Act
The incidental take question remains unresolved in a stable way. Federal circuit courts have split on the issue, and future administrations may reverse the current policy direction. This instability makes the MBTA’s practical reach uncertain for regulated industries and conservation advocates alike.
Who Enforces the Act and How
The U.S. Fish and Wildlife Service, housed within the Department of the Interior, is the primary enforcement agency. Its Office of Law Enforcement employs special agents and wildlife inspectors who investigate violations, conduct undercover operations, and inspect shipments of wildlife at ports of entry. The agency also works with state fish and wildlife agencies, which often have their own complementary laws protecting migratory birds.
Enforcement is, by all accounts, resource-constrained. The Fish and Wildlife Service’s law enforcement division covers the entire country with a few hundred agents, and migratory bird cases compete for attention with investigations into wildlife trafficking, endangered species violations, and other priorities. Major enforcement actions tend to focus on commercial operations, large-scale industrial kill events, and cases with significant public visibility. Individual violations, like someone possessing a feather or disturbing a nest during a home renovation, are almost never prosecuted unless they involve rare or endangered species or show a pattern of intentional harm.
Citizen engagement plays a quiet but real role. Reports from birdwatchers, conservation groups, and concerned members of the public often trigger investigations. Organizations like the Audubon Society have historically pushed for stronger enforcement and have used public pressure and litigation to hold both the government and private actors accountable. Environmental litigation under the MBTA and related statutes has shaped much of the Act’s modern interpretation.
Bird Collisions, Power Lines, and Modern Mortality
The threats facing migratory birds today look very different from the market hunting that prompted the original treaty. Habitat loss remains the most significant long-term pressure, but direct mortality from human infrastructure kills enormous numbers of birds every year. Estimates suggest that building collisions alone kill hundreds of millions of birds annually in the United States. Communication towers, power lines, wind turbines, vehicles, and domestic cats add hundreds of millions more.
Building collisions have drawn particular attention because they are concentrated in urban areas where glass-heavy architecture creates hazards that birds cannot detect. The PNAS commentary cited earlier argues that applying MBTA enforcement to building-related mortality could drive adoption of bird-friendly building design standards, much as earlier enforcement pushed the oil and gas industry to cover waste pits.3PubMed Central. To mitigate bird collisions, enforce the Migratory Bird Treaty Act Several cities, including New York, have already passed local bird-safe building ordinances, but a national approach tied to MBTA enforcement would have broader reach.
Power line electrocution is another persistent problem, and the effectiveness of mitigation measures is uneven. A study of power lines in Mongolia’s Gobi Desert found that perch deterrents, one of the most commonly used mitigation devices, reduced electrocution rates for small birds but were ineffective for medium-sized birds. Some types of deterrents actually increased electrocution risk for certain species.4Avian Research. Avian-power line interactions in the Gobi Desert of Mongolia: are mitigation actions effective? While that study focused on Mongolian infrastructure, its findings speak to a broader challenge: mitigation technologies that work for one group of birds may fail for another, and blanket solutions can create false confidence.
Wind energy presents a more politically complex collision between environmental goals. Wind turbines kill birds and bats, and some of the species most affected, like golden eagles, are protected under both the MBTA and the Bald and Golden Eagle Protection Act. The Fish and Wildlife Service has developed guidelines and permit frameworks for wind energy companies, trying to balance renewable energy development with bird conservation. Eagle take permits allow a limited number of eagle deaths at wind facilities in exchange for compensatory mitigation, such as retrofitting power poles elsewhere to reduce electrocution deaths. The tension between clean energy and wildlife protection is one of the more difficult policy puzzles the MBTA framework currently faces.
How the Act Has Shaped Bird Conservation
Whatever its enforcement challenges, the MBTA’s conservation legacy is substantial. The Act created the legal and institutional framework that made modern waterfowl management possible. Population monitoring programs, flyway management systems, and habitat conservation initiatives all trace their origins to the responsibilities the Act placed on federal agencies.1The Journal of Wildlife Management. The migratory bird treaty and a century of waterfowl conservation The North American Waterfowl Management Plan, a continental habitat conservation strategy launched in 1986, grew directly out of the cooperative framework the treaties established.
Funding mechanisms tied to the MBTA and its associated treaties have also been critical. The Federal Duck Stamp Program, which requires waterfowl hunters to purchase an annual stamp, has raised over a billion dollars since its creation in 1934. Those funds have been used to acquire and protect millions of acres of wetland habitat. The Pittman-Robertson Act, while separate from the MBTA, channels firearms and ammunition excise taxes into wildlife conservation and works in concert with the MBTA’s regulatory framework.
The Act’s influence extends beyond waterfowl. By establishing the principle that migratory birds are a shared international resource requiring federal protection, the MBTA created a model that influenced wildlife treaty-making worldwide. The Convention on Migratory Species, an international treaty with over 130 parties, operates on a similar premise of shared responsibility for species that cross national borders.
Native American and Indigenous Rights
The intersection of the MBTA with indigenous rights has been a sensitive and evolving area. Many Native American and Alaska Native communities have cultural and spiritual practices that involve eagle feathers and other bird parts. For decades, indigenous people faced the prospect of criminal prosecution for possessing feathers and items central to their religious practices.
The federal government has addressed this in part through the National Eagle Repository, a facility in Colorado that collects dead eagles and distributes feathers and parts to enrolled members of federally recognized tribes for religious purposes. Wait times for feathers from the repository have historically been long, sometimes stretching to years, which has frustrated tribal members and prompted calls for reform.
The Religious Freedom Restoration Act and various executive orders have also shaped how the MBTA is applied to indigenous communities, generally pushing toward accommodation. But the fundamental tension persists: the MBTA’s strict possession prohibitions can conflict with treaty rights and religious freedoms that predate the Act by centuries. Courts have navigated these cases individually, and the legal landscape remains a patchwork rather than a clean resolution.
Species Not Covered and Common Confusion
One of the most frequent points of confusion about the MBTA is which birds it actually covers. The short answer is nearly all native species, but the exceptions trip people up. House sparrows, European starlings, and rock pigeons are not protected because they are non-native, introduced species. Mute swans, also introduced, were added to the protected list in 2005 after years of debate, though management of their growing populations remains contentious in several states.
Domestic birds raised for agriculture, like chickens and turkeys, are obviously not covered. But feral populations of formerly domestic species can create gray areas. Feral pigeons roost on buildings and under bridges alongside native species like peregrine falcons that are fully protected. A building manager dealing with bird problems needs to know which species are involved before taking action, because removing a pigeon nest has different legal consequences than disturbing a falcon nest.
Game birds present another area of common confusion. Species like ducks, geese, doves, and woodcock are protected under the MBTA year-round, but they can be legally hunted during designated seasons under state and federal regulations. Outside those seasons, the full prohibitions apply. Picking up a duck feather in July is technically the same violation as picking one up in January, even though you could have legally shot the duck in October.
Raptors occupy a special niche. They are protected under the MBTA, and eagles receive additional protection under the Bald and Golden Eagle Protection Act. Falconry is legal but requires a separate permit and adherence to detailed regulations covering the capture, housing, and use of raptors. The permitting requirements are strict enough that falconry in the United States is effectively a heavily regulated privilege rather than a casual hobby.