Expanding Management of Conflicts Associated with Double-crested Cormorants

What is a double-crested cormorant?

The double-crested cormorant (Phalacrocorax auritus) is a long-lived, colonial-nesting waterbird native to North America. One of 38 species of cormorants worldwide, and one of six species in North America, it is usually found in flocks and is sometimes confused with geese or loons when on the water.

Where do double-crested cormorants live?

Cormorants can be found in many locations throughout North America, including along the coast and inland on lakes, rivers, and other water bodies. The largest concentrations of double-crested cormorants are found on the Great Lakes and the lakes of the Canadian prairie provinces.

How do double-crested cormorants nest?

Cormorants breed in colonies ranging from several pairs to a few thousand. They build their nests of twigs and branches beginning in the spring, usually in trees or on the ground, on islands also favored by other colonial nesting birds, such as great blue herons, great egrets, black-crowned night-herons, cattle egrets, gulls, and terns. Typically, at age three or four, adults are mature and able to breed successfully. Eggs are laid two to four weeks after arrival in the spring, and hatching occurs approximately 30 days later. A typical nest has two or three chicks. These chicks can fly at five to six weeks old and will accompany adults to feed at seven weeks. They are independent of the adult birds at ten weeks.

How abundant are double-crested cormorants in North America?

Cormorant abundance in North America has increased dramatically since the 1960s and 1970s, mostly due to the growth of the Interior and Atlantic subpopulations. The increase in abundance has largely been attributed to better environmental regulations, primarily restricting use of chlorinated hydrocarbons (e.g., DDT), protection under the MBTA in 1972, and decreases in take, compared to the early twentieth century. The current estimate of cormorant abundance in the continental U.S. and Canada is 871,001 to 1,031,757 birds (see Table 2 in the final EIS).

Will the population of double-crested cormorants continue to increase?

The total population of cormorants will continue to increase in the short term although at a slower rate than in past years. In the long term, the population will likely stabilize due to factors such as disease, lack of available nesting habitat, or limitations on food resources. Because cormorants are not typically preyed upon by other species, their populations are regulated primarily by these factors rather than by predation.

Are double-crested cormorants protected in the U.S.?

Double-crested cormorants are protected under the Migratory Bird Treaty Act (MBTA), which involves four international conservation treaties that the United States entered with Canada, Japan, Mexico, and Russia. The MBTA prohibits the take (killing, capture, selling, trading, transport, etc.) of protected migratory bird species without prior authorization by the Service. Double-crested cormorants were first protected in 1972 through an amendment to the Mexican treaty.

What do double-crested cormorants eat?

Cormorants eat mainly fish. Adults eat an average of one pound per day, usually composed of small (less than 6 inches) bottom-dwelling or schooling “forage” fish. They are opportunistic and generalist feeders, preying on many species of fish but concentrating on those that are easiest to catch. Because the ease with which a fish can be caught depends on a number of factors (distribution, relative abundance, behavior, etc.), the composition of a cormorant’s diet can vary considerably from site to site and throughout the year.

Do double-crested cormorants negatively impact fish populations in open waters?

Cormorants are just one of many factors that can affect fish populations. Other factors include water quality, aquatic habitat, predation, and angler catch. Generally, cormorants eat fish species that are not valued by sport and commercial anglers but there are exceptions to this rule. A limited but growing body of research has shown that cormorants can take numbers of sport fish significant enough to have a negative impact on catch rates and in some cases, management can reduce those impacts and benefit fish populations. However, additional research in this area is needed to improve our understanding of the relationship between cormorants and their prey populations.

Do double-crested cormorants significantly affect vegetation and other birds?

In certain circumstances, cormorants inadvertently kill trees, shrubs, and other vegetation due to the accumulation of their guano (which is highly acidic) and the removal of foliage for nesting material. If foliage destruction is common in the area, then the ecological impact is relatively low, though some people may have concerns about damage to the aesthetic value of a particular local site. But cormorant damage to vegetation can be ecologically significant, as it is on some islands of the Great Lakes. There, cormorants are causing severe damage to Carolinian vegetation (deciduous hardwoods found in more northern zones), which is the rarest type of vegetation in the Great Lakes. In addition, cormorants can impact waterbird populations, particularly in the Great Lakes states and provinces, but this is not common.

Does the U.S. Fish and Wildlife Service control double-crested cormorants when they cause damage?

Yes, the Service plays a major role in controlling cormorants in order to prevent and reduce damage. We authorize the take (killing, capture, selling, trading, transport, etc.) of cormorants by issuing the following permits (under 50 CFR):

• § 21.23 (scientific collecting permits),
• § 21.41 (depredation permits, including those specifically for airports),
• § 21.27 (special purpose permits), and now
• § 21.28 (special double-crested cormorant permit for states and tribes).

With one of these permits, an individual or agency can take cormorants, their eggs, and nests in order to alleviate specific damages. To receive a permit, an individual or agency must apply for the permit, demonstrate or describe how damage has occurred, and have tried a variety of non-lethal management activities that have proven ineffective. Before issuing a permit, the Service determines . . .

1.  that the authorized take will have a reasonable chance of resolving the damage, and
2. that the take will not have a significant negative impact on the cormorant population.

The Service can undertake control of cormorants on lands that it owns (such as national wildlife refuges and national fish hatcheries), but it normally does not conduct cormorant control activities on other public or private lands.

The Service may also issue permits to take cormorants if there is convincing evidence that cormorants are negatively affecting species deemed to be important, or rare and declining plant communities at a local scale.

Does the U.S. Fish and Wildlife Service allow the control of double-crested cormorants at aquaculture facilities?

Yes. Cormorant damage at aquaculture facilities is managed under a depredation permit system, whereby the Service permits the lethal take of double-crested cormorants at commercial freshwater aquaculture facilities when non-lethal methods are insufficient in preventing depredation.

The current depredation permit under 50 CFR 21.41 does not include authorization of take for wild or publicly stocked fisheries. However, the Service can issue the new special double-crested cormorant permit (50 CFR 21.28) to a state or tribal fish and wildlife agency to address the depredation of wild and publicly stocked fish managed by the agency.

How will the U.S. Fish and Wildlife Service keep track of double-crested cormorant populations to ensure that they remain at sustainable levels?

Several federal, state, and tribal entities are involved in monitoring or counting cormorant populations, and this gives those who manage the birds, critical information about population changes and the current population status of the species. The actual monitoring is conducted by the U.S. Fish and Wildlife Service, USDA Wildlife Services, the Canadian Wildlife Service, state wildlife agencies, and various universities. We use various types of surveys including (but not limited to) the Great Lakes Colonial Waterbird Survey, the Atlantic Coast Colonial Waterbird Survey, winter roost surveys, Christmas Bird Counts, and Breeding Bird Surveys. The U.S. Geological Survey and various non- governmental organizations help by recording and analyzing the population counts from the surveys.

The Service will work with the four Flyway Councils, states, tribes, and partnering federal agencies to develop standard protocols for monitoring cormorant numbers. The Service and our partners will complete these protocols within approximately one year of the publication date of the final rule that issued the new special double-crested cormorant permit (date of publication: December 29, 2020).

What happened to the depredation orders?

In response to ongoing damage at aquaculture facilities and other damage and conflicts associated with cormorants, from October 2003 until May of 2016, the Service administered the following regulations:

• Aquaculture Depredation Order (which was located at 50 CFR 21.47)
  
  This Order eliminated individual permit requirements in 13 states for private individuals, corporations, state agencies, and federal agencies taking cormorants at aquaculture facilities.
• Public Resource Depredation Order (which was located at 50 CFR 21.48)
  
  This Order enabled states, tribes, and the U.S. Department of Agriculture's Wildlife Services in 24 states, without individual depredation permits, to take cormorants 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.

In May of 2016, the U. S. District Court for the District of Columbia vacated the two depredation orders described above. The Court concluded that when creating that system of regulations, the Service had not sufficiently considered the effects of the depredation orders on cormorant populations and other affected resources, and that the Service had failed to consider a reasonable range of alternatives in the environmental assessment issued under the National Environmental Policy Act (NEPA) of 1969 (as amended in 2014). Because of the Court’s decision in 2016, the authority for authorizing lethal take of depredating cormorants then reverted back to the previous system of individual depredation permits under 50 CFR 21.41. Those depredation permits could be issued only to alleviate cormorant impacts on:

1. health and human safety,
2. aquaculture,
3. property damage, and
4. concern for co-nesting threatened and endangered species.

The new special double-crested cormorant permit (50 CFR 21.28) is a permit issued to a state or tribal fish and wildlife agency to authorize take of double-crested cormorants for:

1. depredation of fish at state or tribal-owned and operated aquaculture facilities and hatcheries;
2. human health and safety on lands or in waters managed by a state or tribal fish and wildlife agency;
3. threats to the recovery of protected wildlife (including threatened and endangered species or those listed as Species of Greatest Conservation Need in State Wildlife Action Plans);
4. damage to agency property; and
5. depredation of wild and publicly stocked fish managed by the agency.

Is the U.S. Fish and Wildlife Service increasing the number of cormorants that are allowed to be lethally taken each year?

Yes. The Service developed a Potential Take Limit (PTL) model to determine the number of cormorants that can be taken in the contiguous 48 United States. The PTL model estimates the maximum number of cormorants that can be taken each year, given the management objectives and desired population size. This largest number that can be taken (called the “maximum allowable take”) is not a prescribed take level for cormorants; rather, it is the predicted maximum allowable level of annual take. The PTL corresponds with a biologically sustainable level of annual take based on knowledge of cormorant population dynamics. Under the final rule that establishes the new permit, the maximum allowable take of cormorants totals 121,504 cormorants per year within the lower 48 states. The maximum allowable take levels for the four subpopulations of cormorants are as follows: Atlantic (37,019); Interior (78,632); Western (4,539); and Southern (Florida) (1,314). The Service indicates for each permit we issue, the number of cormorants allowed to be taken under that particular permit.

Does the new permit address free-swimming fish?

In previous Service workshops and the 2018 workshop summary, the phrase “free-swimming fish” was used. However, the ambiguity of this phrase caused confusion. Since that time, the Service refined the phrase to “wild and publicly stocked fisheries” so that it is clearer to stakeholders and represents the variety of fisheries covered under the new permit. The final rule and final Environmental Impact Statement address publicly stocked fish (fish stocked by public or state agencies for public use) and tribally stocked fish (fish stocked by tribes for tribal use).

Does the new permit address private ponds and private property?

Yes, in some instances, the Service does allow the take of migratory birds to protect private property. Private landowners may apply for a depredation permit (50 CFR 21.41) to alleviate damage to some types of property (buildings and infrastructure, vehicles and equipment, and some types of vegetation). However, by policy, the Service’s Migratory Bird Program does not issue permits to prevent depredation or harm to privately owned animals (for example, hobby animals, pets, or similar categories of animals) that are raised free-range or otherwise released to the wild. Numerous nonlethal methods are available to landowners who maintain animals in natural-like environments—methods such as harassment, habitat modification, and others described in Appendix 3 of the Service’s 2017 Environmental Assessment.