Cormorants Blamed for Hard Times
Double-Crested Cormorants have a long, controversial history in Minnesota. Once plentiful with large colonies across the state, depredation efforts in the early 20th century reduced numbers significantly. These birds are increasingly the focus of debate about population management of migratory bird populations.
The Double-Crested Cormorant is approximately the size of a small goose, with a wingspan of up to 54 inches. They have black, rounded bodies and long, thick necks, and can be found near water, swimming or perched, often with its wings outspread.
Cormorants in Minnesota eat a variety of fish, generally 5.3 inches or shorter. Common species include brook stickleback, logperch, yellow perch, sunfish, cisco, white suckers, black bullheads, white crappies, crayfish, northern pike, walleyes, and tiger salamanders. Despite common beliefs, walleyes and northern pike together made up less than 1 percent of the cormorant's diet. Much animosity toward cormorants is driven by the belief that they consume these recreational fish, but in reality cormorants are only one part of a complex food chain.
Historical and Ecological Perspective
As Cormorant populations recovered in the late 20th century, increased consumption was perceived to negatively affect recreational opportunities and local businesses. Because of this, cormorants in Minnesota are managed to protect private resources. On Lake Waconia and Wells Lake, cormorants are managed on nesting islands that are also used by Great Egrets, Great Blue Herons and Black-crowned Night-Herons.3
While protected under the Migratory Bird Treaty Act, national concerns over Double-crested Cormorants have resulted in 2003 in the Public Resource Depredation Order, allowing take of cormorants demonstrated to be impacting public resources.Additionally, operators of commercial aquaculture facilities are allowed to kill cormorants that threaten their stocks, since minnows are reared in shallow ponds where cormorants feed.
Such management must be sensitive to impacts on related species. On a few lakes in Minnesota, cormorants share habitat with other colonial waterbirds, including Great Egrets, Great Blue Herons, Black-crowned Night-Herons, and the American White Pelican. Such diversity is not commonly found, making such sites particularly important resources for Minnesota’s colonial waterbird community.6 (Lake Waconia and Wells Lake Colonial Waterbird Surveys 2011-Final Report to Minnesota Department of Natural Resources). Because nesting associates at cormorant colonies are the most likely to be impacted by cormorant control activities, other colonial waterbirds that are protected as migratory birds may also be affected by depredation of cormorants.
Control in Minnesota
In Minnesota, cormorant management has proceeded under these permits at Wells Lake in 2007 and at Lake Waconia in 2008. Ongoing control at these lakes has annually increased the number of cormorants killed, with monitoring to measure the impact of efforts on fisheries, other wildlife, and habitat.
Despite the increasing take of cormorants in Minnesota’s lakes, communities such as Waconia, a short distance west of the Twin Cities, blame the birds for decreasing levels of game fish and related economic hardship for recreation businesses. Yet the Minnesota DNR biannual survey confirms an average-to-high number and weight of Walleye, Northern pike, Largemouth Bass, Crappies and Bluegill. Furthermore, herons and egrets in the same area have not been targeted for their impact on the fishery. Yet the historically hated cormorant continues to bear the blame for hard times.
Such criticism has led to political pressure to further restrain cormorant populations. Recent proposals in the U.S. House of Representatives threaten to remove the Double-crested Cormorant from the list of birds protected by the Migratory Bird Treaty Act (MBTA). One new bill by Congressman John Kline (MN District 2) would delegate management from the Secretary of the Interior to any State that has an alternate management plan approved. (HR 3074)
Removing cormorants from the MBTA will leave this species no legal protection in Minnesota, since the State does not provide the bird with protection in its statutes. Without legal protection against wholesale slaughter of the birds, negative public perception would likely lead to destruction of their eggs, young, and nests. Even an approved management plan at the State level will not provide the comprehensive management that migratory birds require as they move between regions, and likely would bend to local pressures to severely decrease populations in sensitive areas.
Audubon’s Position on Legislation
The Migratory Birds Treaty Act is one of Audubon’s longest standing achievements, created in 1918 in response to the destruction of large numbers of waterbirds. Past experience has shown that we cannot leave our wildlife without adequate legal protection or we risk losing them.
Audubon adamantly opposes cormorant “control” programs that do not sufficiently take into account data on the bird’s actual effect on fish populations, pose a threat to other colonial nesting species, or are the result of emotional hysteria. This current legislation is not based in science nor balanced for ecological impacts, but is merely a response to common misperceptions about seeming declines in recreational and commercial fishing.
There is no justification for the removal of cormorants from the protection of the Migratory Birds Treaty Act. This Act is at the foundation of Audubon’s mission to protect wildlife populations, which includes responsible population control. There is no scientific evidence that cormorants are having a major impact on the fishing economy, but rather the repeated refrain that there are simply “too many” birds.
Audubon Minnesota supports the existing Double-crested Cormorant depredation plan that provides ongoing monitoring, scientifically supported correlations in bird populations and fish decline, control activities that do not negatively affect non-target species, and consideration for statewide and regional impacts.
Setting bird population goals based on fisheries goals is contrary to good bird management and sets a harmful precedent. Fish-eating birds will become an exception to national protections if natural resource agencies manage them to meet fishery objectives.
The Migratory Bird Treaty Act is one of the longest standing protections of birds, hard won in the early years of the National Audubon Society by citizens calling for comprehensive protections of migratory birds. Unfounded objections to local cormorant populations must not be allowed to drive dangerous legislative precedent.
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