The Cormorant Conflict

  • Nathan LaFramboise
  • Animal Legal & Historical Center
  • Publish Date: 2006
  • Place of Publication: Michigan State University College of Law


Can we predict how the migratory, double-crested cormorant population will be managed through international law, when the United States perceives the rise of the cormorant population an economic and biological threat, but where Canada views the cormorant’s comeback a biodiversity success story?


[Click here for link to photos of cormorants] [1]



The double-crested cormorant, Phalocrocorax auritus, is a bird some people love to hate because of its sinister appearance and its presumed propensity to prey on beloved game fish. [2]  The cormorant, or crow-duck as referred to in Canada, can be found from Southwest Alaska as far south as the Gulf of Mexico when the cormorant migrates for the winter. 


[Click here for a link to a map of the United States and Canada showing the winter distribution of double-crested cormorants] [3]


Cormorants are similar to the loon in their size, appearance, and their hunting of fish. However, cormorants are more gregarious as they nest and hunt in large numbers.  Sea gulls, foxes, and raccoons are the primary predators of cormorant eggs and chicks, while the adult cormorants are susceptible to predation by bald eagles and the occasional owl [4].  Cormorants eat primarily fish less than six inches.  Cormorants prey on perch, walleye, small-mouth bass, northern pike, sunfish, bluegill, crappie, and other small fish depending on the cormorant’s location.  Cormorants eat on average one pound of fish per day in their adult lives.  Thus, the concern is that the cormorant is substantially reducing the numbers of commercial and recreational fish available. [5]


[Click here to link of cormorants on coastal rocks] [6]


The cormorant population has gone through some interesting cycles during the past 100 years.  The early twentieth century saw plentiful numbers of cormorants.  Some reports in Minnesota cite hundreds of thousands cormorants migrating north along the Mississippi River. [7]  The cormorants colonized the Great Lakes throughout the 1920’s and stayed until the 1950’s before the eventual decline of the cormorant.  The decline of the cormorant came as a result of reproductive failures, which were caused by the high level of toxic chemicals, mainly DDT and PCBs, found in the freshwater throughout the regions the cormorant inhabited. [8] The DDTs and PCBs toxins infected the cormorant after the consumption of numerous contaminated fish.  The consumption of the contaminated prey caused the cormorant’s egg shells to thin, which resulted in as much as 95% of egg breakage in some reported areas around the Great Lakes during this period. [9]


[Click here for a graph showing egg-shell thinning in cormorant populations from 1940 – 1990] [10]


However, the cormorant population rebounded during the middle to late 1970’s.  The dramatic increase was due, in large part, to the reduction of toxic chemicals and the increase in the number of smaller fish. 


[Click here for a graph showing DDE levels in cormorant eggs from 1971 – 1989] [11]


Today over 600,000 cormorants are reported to be nesting around the Great Lakes in contrast to the reported 200 cormorants on the Great Lakes in the early 1970’s. This rapid increase in population has led to an examination of whether the cormorant is an actual problem or merely a perceived issue.  The United States views the overpopulation problem of cormorants as two-fold.  First, is the problem of the cormorant’s adverse biological impact.  Cormorants adversely impact fish species, other bird species through competition for nesting, and vegetation where nesting. Second, is the adverse socioeconomic impact of the cormorant.  The cormorant interferes with aquaculture producers, commercial fisheries, fish-related business, and water quality [12].  Because of these problems, actual or perceived, the US Fish and Wildlife Service is looking at numerous possible solutions to control the cormorant population.  The US Fish and Wildlife Service considered non-lethal management, regional population reduction, and a possible hunting season.  In the 2003 environmental impact statement (EIS) issued by the Service that outlined alternative plans for cormorant management, the Service recommended the issuance of public and aquaculture resources depredation orders.  These orders would allow designated state and federal agents who see cormorants taking fish resources to kill these birds.

Alternative D, the selected action, creates a public resource depredation order to authorize State fish and wildlife agencies, Federally recognized Tribes, and APHIS/WS to take DCCOs found committing or about to commit, and to prevent, depredations on the public resources of fish (including hatchery stock at Federal, State, and Tribal facilities), wildlife, plants, and their habitats. This authority applies to all lands and freshwaters (with appropriate landowner permission) in 24 States (Alabama, Arkansas, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Michigan, Minnesota, Mississippi, Missouri, New York, North Carolina, Ohio, Oklahoma, South Carolina, Tennessee, Texas, Vermont, West Virginia, and Wisconsin). [13]

As might be expected, the EIS was followed by the issuance of depredation orders in October of 2003 that allow agents to kill cormorants that are taking or threatening to take fish at aquaculture facilities as well as cormorants that are threatening public resources. [14]  While the depredation order for public resources requests the application of non-lethal methods first, lethal control methods, including egg and nest destruction, cervical dislocation, and killing by firearms, are authorized. [15]  These depredation orders remain in existence until April 30, 2009 unless revoked or extended prior to that date. [16]  The proposed action originally detailed in the US Fish and Wildlife Service’s environmental impact statement would require killing approximately 150,000 cormorants. [17]

In Canada, however, where the cormorant is regulated provincially, Ontario has not come to the same conclusion.  Ontario views the return of the cormorant as a success story and views the cormorant as an integral part of its ecosystem. 

The cormorant is a native species in Canada. There is a biological principle that states that the greater the number of different organisms an area can support, i.e. the more diverse the wildlife, the better the area. This is known as biodiversity. The richest areas in the world for biodiversity are the tropics...moist, warm areas the year 'round. The temperate zone areas, where we live and where the Great Lakes are located, are comparatively poor in biodiversity. We have lost many species from the Great Lakes already...the Atlantic Salmon, the Blue Pike, the Passenger Pigeon, the Whooping Crane...we don't need to lose anymore. [18]           

Because of the conflicting approaches of the two countries involved in cormorant management, it is important to look to international law to see if the United States and Canada can proceed in this matter with their national interests in mind or whether the solution lies in international law.



The Cormorant is protected under the 1916 Migratory Bird Treaty with Canada, indirectly under the Ramsar Convention, and the Migratory Bird Treaty Act of 1918 (MBTA).   The cormorant receives no protection from the Convention of Migratory Species or CITES.

The Migratory Bird Treaty with Canada came from the Convention Between the United States and Great Britain (for Canada) for the Protection of Migratory Birds.  This treaty protects birds that migrate between the United States and Canada.  The language of the treaty extends protection to birds either harmless or beneficial to man and prohibits hunting of these birds, but the treaty does allow killing migratory birds, under permit, when they adversely impact agriculture.  The treaty was amended in 1995 to provide a legal framework for subsistence take of birds in Alaska and Canada by Alaskan natives and Canadian Aborigines [19].  

The Ramsar Convention was adopted in Ramsar, Iran in 1971, and is signed by over 147 contracting parties.  The United States ratified Ramsar in 1986, and Canada ratified in 1981.  The goal of Ramsar is to promote the wise use and sustainable development of all wetlands through regional and international cooperation [20].  The convention is self-implementing with the U.S. Fish and Wildlife Service serving as the administrative authority in the United States; Canada administers Ramsar through the efforts of the Canadian Wildlife Service and provincial governments.

Under the Ramsar Convention, states list wetlands of international importance, and then parties are required to promote the conservation and wise use of that wetland.  Furthermore, Ramsar requires that parties establish nature reserves on the protected wetlands thereby providing a sanctuary for wetland species.  Article 4 of Ramsar requires that each contracting party shall promote the conservation of wetlands and waterfowl.  Ramsar, through its protection of wetlands, has implemented an agreement that benefits waterfowl.

While the Ramsar Convention and the Migratory Bird Treaty with Canada remain possible avenues for international protection of the cormorant (see infra), it is the Migratory Bird Treaty Act of 1918 (MBTA) that is the primary instrument of international law concerning the migratory birds in North America.  The Migratory Bird Treaty Act of 1918 implemented the 1916 Migratory Bird Act with Canada.  The MBTA also implemented treaties between the United States and Mexico, Japan, and the former Soviet Union.  The purpose of the MBTA is to aid in the restoration of migratory birds where the birds have become scarce or extinct, and also to regulate the introduction of American or foreign birds or animals in places where they have not previously existed. [21]  The treaty, unless permitted by regulation, provides that, “It is unlawful to pursue, hunt, take, capture or kill; attempt to take, capture or kill; possess, offer to or sell, barter, purchase, deliver or cause to be shipped, exported, imported, transported, carried or received any migratory bird, part, nest, egg or product, manufactured or not.” [22] Authority to decide which birds are considered “migratory” for purposes of the Act is delegated to the Fish and Wildlife Service who then publishes this list in the Code of Federal Regulations. [23]  In 2004, the Consolidated Appropriations Act amended the MBTA such that only “native” migratory bird species (e.g., those species that appear in the United States as a result of natural (non-human assisted) biological or ecological processes) are included for protection under the Act. [24]  For purposes of the new Migratory Bird Treaty Reform Act (MBTRA), the double-crested cormorant is a native species protected under the Act. [25]  However, the treaty allows states to determine when a migratory bird can be taken so long as the state has regard for temperature zones, distribution, abundance, economic value, breeding habits and migratory flight patterns. [26]

As with most international treaties, some of the most important language can be found in the enforcement and penalties provisions.  The enforcement and penalties provisions of international treaties, if articulated correctly, should have the necessary deterrent effect to accomplish the goal of the treaty, as intended by the drafters, which is the preservation of migratory birds.  The MBTA enforcement provision focuses on individual and corporate violators. [27] This provision provides the potential fines and possibly prison time for violators of the MBTA.  Thus, it is interesting that this MBTA provision has no guidance for state violators, or a framework to decide if a state is violating the MBTA.  The only treaty language that is directed toward state actors is found in 16 USC 708. [28]  Section 708 provides that states, when regulating migratory birds, “shall give further protection to migratory birds, their nests, and eggs.”(Emphasis added)  But, ultimately, the MBTA lacks any guidance to the sanctions or penalties that would be imposed by a state violating the MBTA. 

It should be noted that while the Convention on International Trade in Endangered Species (CITES) and The Convention of Migratory Species (CMS) are two of the more respected examples of international law, they do not apply to the cormorant.  The Convention on Migratory Species is inapplicable international law because neither Canada nor the United States is an official member of CMS.  If the CMS was applicable, it would seem to require an international agreement before the United States could unilaterally manage the cormorant. CITES deals with the trade in endangered species and CITES is inapplicable to the cormorant conflict because the cormorant is not endangered, and there is currently no demand for international trade of the Cormorant as whole or any specimen of the cormorant, which CITES would cover.  To be sure, CMS and CITES are inapplicable international laws when dealing with the management of the cormorant between the United States and Canada.



While the migratory nature of the cormorant results in its enhanced protection under international law, it also raises inherent management conflicts between the two sovereign nations it calls home.  It is the issue of how the international treaties are applied, or in some case not applied, that truly affects the status of the cormorant in North America.  Because treaties attempt to foster cooperation between nations, issues of management in the home countries are usually left to those nations.  This in essence creates a disconnect between the laudable goals of the treaty and the practical application of its terms.    

This is best illustrated by the Ramsar Convention.  The Ramsar Convention protects wetland habitat and provides a nature reserve for all organisms in the wetlands.  It would appear then that any cormorant within a protected wetland would be protected from potential population management efforts by the United States.  However, Ramsar creates room for legislative interpretation because the Ramsar Convention fails to define what it means when contracting parties are required to promote the “wise use” of wetlands.  If the “wise use” requirement is similar to the modern term “sustainable development,” then the United States could drastically deplete the cormorant population to a level that still guarantees the sustainability of the cormorant.  Under this sustainable development philosophy, the United States, for an extreme example, could arguably wipe out hundreds of thousand cormorants because there would still be a cormorant population that guarantees sustainable development for the future.  Thus, one proposed plan of action from the US Fish and Wildlife Service, which called for more than 150,000 birds killed, could be justified by not affecting the sustainability of the cormorant for the future. Canada would probably not even try to arbitrate this matter because it appears the United States is acting within the letter of the Ramsar Treaty, even if selective eradication of the cormorant violates the spirit of the Ramsar Convention.

Again, the most relevant treaty in this conflict is the MBTA of 1918.  While the MBTA provides migratory birds with protection from unauthorized killings it maintains flexibility for states in regulating migratory bird issues.  According to the MBTA the “take” of cormorants is illegal except pursuant to state regulations.  The MBTA gives regulatory power to the US Fish and Wildlife Service in the United States with obligations to conserve and manage migratory birds by maintaining healthy populations of migratory birds. [29]  The MBTA does not have a central body that determines the desired population of cormorants or any migratory bird.  Thus, the United States has almost infinite room to manage the cormorant (according to the best available scientific principles as determined by USFWS biologists) as the United States deems appropriate because the US Fish and Wildlife Service gets to determine the desired population of cormorants.  Furthermore, as long as the United States keeps the cormorant population “healthy” by its own definition, the United States does not facially violate the MBTA, and Canada has to accept the possible depletion of the cormorant population.  Even if the United States was in violation of the MBTA, the MBTA lacks the appropriate enforcement and penalties provisions in circumstance where state actors are in violation of the MBTA.

In essence, there is no international law that prevents the United States from reducing the migratory cormorant population to a level that Canada finds unacceptable. The language of the Ramsar Convention, though it may protect cormorant populations indirectly, is not concise enough to prevent the selective eradication of cormorants because its “wise use” is debatable.  The Migratory Bird Treaty Act delegates sufficient regulating deference to states, thereby permitting states to enact any rational basis regulation, which seemingly will hardly ever violate the MBTA, unless the regulation is substantially detrimental to the betterment of migratory birds.  The Migratory Bird Treaty Act also fails to set forth penalties or procedures when determining whether a state actor is in violation of the act.  Thus, the United States can, simply by legislation or federal rule, allow the killing of cormorants in order to meet the economic needs of selective interest groups because of a conflict between man and bird.  Canada, with biodiversity as its goal, will just have to hope that the cormorant survives the migration through the United States in the spring because Canada has no international legal framework in place to stop the United States from furthering its domestic policy of eradicating the cormorant.



Ideally, the best recommendation would create an international management of the cormorant that would satisfy both Canada’s effort to promote biodiversity and solve United States’ biodiversity and socioeconomic problems caused by the cormorant population.  In reality, a recommendation that satisfies both Canada and the United States is impracticable, as the USFWS prioritizes the protection of aquaculture facilities above that of species preservation.  However, there are some courses of action that could prove to be beneficial in finding an appropriate middle ground in the cormorant conflict between Canada and the United States.

The first course of action should be to educate the American sportsman with accurate facts about the cormorant and its relationship to the overall ecology of the aquatic ecosystem.  The sportsman may see the cormorant taking fish in an area depleted due to a host of other environmental factors, but it is the cormorant who becomes the scapegoat for the perceived reduction of stocks.  Initially, it is important that those lobbying for the eradication of the cormorant to know that the bird is native to North America.  Because of the recent boom in population, some sportsman consider the cormorant to be an evasive species, similar to the zebra muscle found in the Great Lakes, that consumes five times its body weight in fish each day, but this is inaccurate speculation.  It is critical to spread fact about the cormorant over inaccurate perception.  Second, the public should be aware of the cormorants past population history because of the effects of DDT in America’s freshwater.  The North American cormorant is a species that was on the brink of extinction but now has rebounded due to the efforts to preserve North America’s freshwater.  Finally, the American population should be reminded of the benefits of biodiversity.  Though benefits of biodiversity are not always obvious, the United States should not be so quick to eradicate a cormorant population without fully understanding its role in a complex ecosystem.

The second course of action should be to suggest Canada try to amend the MBTA.  The MBTA should be amended to include a section that provides a framework or procedure for interstate disputes regarding the management of migratory birds.  The birds protected under the MBTA should not be subject to a substantial reduction in population, unless there is a consensus between all parties to the MBTA.  Considering the few nations included in the MBTA, a consensus could more easily be accomplished compared to some of the larger international treaties.  If a consensus proved to be impossible, then the next step, before a substantial number of migratory birds could be subject to population reduction, should be a negotiated settlement.  Because the MBTA members recognize the importance of migratory birds this simple amendment could act as a check before states are allow to enact regulations that would have a substantial detrimental effect to migratory bird populations.

The third course of action should be to research the cormorant before any reduction in population begins.  Between United States and Canada there is enough capital and resources to thoroughly research the benefits and consequences of the cormorant population as it is today.  Information gained from objective science is the best way to proceed, and information learned through objective science should be given much more weight than political decision.  To be sure, a program to educate American sportsman on the effects of the cormorant population, an amended MBTA, and objective scientific research of the cormorant ideally would provide a solution to this conflict, which would better reflect the interests in all parties involved.

Practically, the United States will begin to reduce the cormorant population unbothered by any international law.  A hunting season will probably occur if the cormorant turns out to be a tasty bird.  Currently in Michigan, citizens can legally harass cormorants with noisemakers in hope of preventing property damage, and citizens can call the Department of Natural Resources to have them oil or destroy cormorant eggs. [30]  This is just the beginning of what will become a proactive approach in controlling the cormorant population throughout the United States.  Biodiversity has clearly taken a back seat to the economic interests of the fishing industry in the United States, and Canada will have live with the consequences of any action taken by the United States.


[1] Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. 2005. The Animal Diversity Web (online). Accessed February 21, 2006 at  (Photograph taken by H. C. Kyllingstad).

[2] Minnesota Department of Natural Resources. 2006. The Minnesota Department of Natural Resources Web Site (online). Accessed 2006-2-21 at (Watching cormorants on a lake, folks assume that every dive wipes out a walleye).

[3] Migratory Bird Research. Winter Distribution Map of the Double Crested Cormorant.

[4] Ward, E. and K. Kirschbaum. 2000. "Phalacrocorax auritus" (On-line), Animal Diversity Web. Accessed November 10, 2005 at

[5] Environment Canada, Ontario Region. The Rise of the Double Crested Cormorant on the Great Lakes. 2005.

[6] Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. 2005. The Animal Diversity Web (online). Accessed February 21, 2006 at  (Photograph taken by Roger Myers).

[7] Minnesota Department of Natural Resources. 2006. The Minnesota Department of Natural Resources Web Site (online). Accessed 2006-2-21 at

[8] Environment Canada, Ontario Region. The Rise of the Double Crested Cormorant on the Great Lakes. 2005.

[9]  Id.  In 1972 researchers discovered that 95% of the eggs in the Lake Huron colonies had broken or disappeared by the end of the incubation period. Toxic contamination was the most likely cause of the widespread reproductive failure among cormorants on the Great Lakes during this period. Similar declines and reproductive failure were noted in other parts of the cormorants range, including Alberta, Minnesota and Wisconsin.

[10] Id.

[11] Id.

[12]US Fish and Wildlife Service. Double Crested Cormorant Final Environmental Impact Statement.  2003.

[13] US Fish and Wildlife Service. Migratory Bird Permits; Regulations for Double-Crested Cormorant Management. 68 FR 58022-01 (October 8, 2003).

[14] See Depredation order for double-crested cormorants to protect public resources. 68 FR 58035 (Oct. 8, 2003) and Depredation order for double-crested cormorants at aquaculture facilities.  68 FR 58034 (Oct. 8, 2003).

[15] Depredation order for double-crested cormorants to protect public resources. 68 FR 58035 (Oct. 8, 2003).

[16] Id.

[17] US Fish and Wildlife Service. Double Crested Cormorant Final Environmental Impact Statement.  2003.

[18] Environment Canada, Ontario Region. The Rise of the Double Crested Cormorant on the Great Lakes. 2005.

[19] US Fish and Wildlife Service. Double Crested Cormorant Final Environmental Impact Statement.  2003

[20] The Ramsar Convention on Wetlands.  2005.

[21] Cornell Law School. Legal Information Institute. 2005.

[23] The double-crested cormorant is currently protected as a migratory bird.  See, 50 C.F.R. 10.13.

[24] For the actual amended language, see the Consolidated Appropriations Act of 2004.  See also 70 F.R. 12710 - 12716 for a final list of bird species to be excluded under the MBTRA.

[25] But note that another cormorant species, the red-legged cormorant, has been excluded under the draft list as a non-native, migratory bird.  70 F.R. 12710.

[26] 16 U.S.C. 704.

[27] 16 USC 707 . Violations and Penalties. Except as otherwise provided in this section, any person, association, partnership, or corporation who shall violate any provisions of said conventions or of this Act, or who shall violate or fail to comply with any regulation made pursuant to this Act shall be deemed guilty of a misdemeanor and upon conviction thereof shall be fined not more than $ 15,000 or be imprisoned not more than six months, or both. 

[28] 16 USC 708. State or Territorial laws or regulations.  Nothing in this Act shall be construed to prevent the several States and Territories from making or enforcing laws or regulations not inconsistent with the provisions of said conventions or of this Act, or from making or enforcing laws or regulations which shall give further protection to migratory birds, their nests, and eggs, if such laws or regulations do not extend the open seasons for such birds beyond the dates approved by the President in accordance with section three of this Act

[29] US Fish and Wildlife Service. Double Crested Cormorant Final Environmental Impact Statement.  2003.

[30]  Michigan Department of Natural Resources. Double – Crested Cormorants in Michigan: A review of history, status, and issues related to their increased population. Report 2, August 2005.


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