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Most-hated bird in the world: Sanctioned killing of cormorants continues unabated in Minnesota

By Mike Mosedale | Thursday, July 17, 2008
Little Pelican Island, which is owned by the Leech Lake Band of Ojibwe, is the site of the state’s largest colony of double-crested cormorants.

Earlier this month, sharpshooters with the U.S. Department of Agriculture’s Wildlife Services wrapped their annual operation at Leech Lake, the sprawling and legendary fishing Mecca in north central Minnesota. In keeping with past practices, the sharpshooters set their sights on a spit of guano-covered rocks and mostly dead vegetation called Little Pelican Island.

Little Pelican, which is owned by the Leech Lake Band of Ojibwe, is the site of the state’s largest colony of double-crested cormorants. And for the last four years, it has also been ground zero for a burgeoning conflict between the fish-eating birds and fish-loving Minnesotans.

Using .22 caliber rifles equipped with silencers—a tactic accommodated by a recent change in state law designed to help with the effort—the sharpshooters managed to “cull” about 2,500 cormorants between ice-out and early July. That raised the four year kill total of the once-endangered birds to over 11,000.

The action came in response to widespread complaints about the resurgent cormorant population on Leech Lake, which, after a century long absence, grew from under 100 birds to a high of over 10,000 in less than a decade. 

At the Minnesota Department of Natural Resources, regional fisheries manager Henry Drewes said he is convinced that four years of cormorant control has helped to hasten the remarkable recovery of walleyes and yellow perch numbers at Leech Lake. Both species went into steep declines around the time the cormorant colony on Little Pelican Island was booming.

“We do know that under lower density of cormorants we’ve seen a dramatic rebound of walleyes,” said Drewes, who also credited intensive walleye stocking and stricter fishing regulations for the comeback. Whatever the cause, gill net sampling last fall yielded the second highest walleye numbers at Leech Lake since such research began a quarter century ago. In two years, Drewes said, perch numbers went from historic lows to historic highs.

Eliminate the birds
Still, according to Drewes, “a diversity of opinions” persists among anglers and resort owners about the cormorant management plan at Leech Lake, which was devised in a collaboration between the Leech Lake Band of Ojibwe, the DNR and the U.S. Fish and Wildlife Service.

Given the recent improvements in the fishing, Drewes said, many people appear satisfied with the current approach, which sets a goal of 500 nesting pairs for the lake. Others, he said, would prefer the cormorants entirely eliminated.

None of that is surprising. At Leech Lake and other places where cormorants have re-established robust populations, especially on the Great Lakes, the prevailing view of the bird is unrelentingly negative.

On the website of one Leech Lake resort, cormorants are characterized as “walleye gorging birds.” Kill-them-all sentiments abound on fishing forums. And on one Internet chat board, an irate Leech Lake fishing guide publicly declared his intentions to take his wrist rocket along on future outings, just in case he was to encounter some of the despised birds. 

“I don’t know if there’s any other bird that people have such a visceral hate for,” observed Dr. Linda Wires, a research fellow at the University of Minnesota who calls the cormorant “the most hated bird in the world.” She suspects this is partly a matter of appearance; cormorants are large, black, and resemble an ungainly cross between a crow and a goose.

But, Wires noted, most of the enmity derives from a centuries-old conflict with sport and commercial fishermen, who, despite shaky evidence, remain convinced that the cormorant’s robust appetite and skills as a predator are wrecking havoc on fisheries.

“You can document four hundred years of this perception in North America that cormorants are this big destructive force,” said Wires. “In fishing communities, there is just such a low tolerance, almost zero tolerance, for cormorants. It doesn’t seem to matter much what the data says.”

Circumstantial case
Indeed, at Leech Lake, the data connecting cormorants to walleye declines is far from definitive. While the circumstantial case appears strong—with the drop in walleyes coming around the time the cormorants expanded—association does not always equal cause, as any scientist will tell you.

Over the past three years, researchers have examined the stomach contents of adult cormorants killed at Leech Lake. Their conclusions? The cormorants typically prefer little fish, mainly yellow perch in the two to six inch range, and walleyes make up a small portion of their diet. Depending on the year, the figure has ranged from less than 1 percent to about 3 percent.

Steve Mortensen, a biologist with the Leech Lake Band of Ojibwe who has worked extensively on the cormorant issue, said the food web in Leech Lake is highly complex, and cautioned against drawing too many conclusions.

“There’s probably some sort of number beyond which cormorants have a negative effect on walleyes,” Mortensen said.  But, Mortensen added, walleye reproduction can be influenced by a lot of factors and poor class years are common, cormorants or no cormorants.

Ironically, Mortensen said, the presence of cormorants at Leech Lake may have even helped the walleye population because cormorants prey so heavily on yellow perch, which in turn often eat juvenile walleyes.

A 2007 report by the Leech Lake Division of Resource Management, which was co-authored by Mortensen, concluded that “the unexpected results of the [diet] study are complicating the justification for culling large numbers of cormorants.”

“There’s still a definite push from the fishermen and the resort community to rid the lake of every cormorant. But they can’t deny that fishing has been good and the walleyes are definitely back,” said Mortensen.

A reprieve?
So will the Leech Lake cormorants get a reprieve next year?

That’s unlikely, said Dr. Wires, the U of M cormorant researcher.

“No matter what the science shows, they are going to manage cormorants because the public puts so much pressure on those agencies,” said Wires. “It’s too important of a fishery and people are convinced that the cormorants are doing damage. You can present all the science you want but they won’t believe it.”

It’s not just at Leech Lake. Across the Great Lakes, growing cormorant numbers have prompted widespread control campaigns at colonies, where corn oil is applied to eggs to prevent them from hatching. According to Wires, such operations are now occurring at 48 of the 100 documented colonies on the Great Lakes. (On Lake Superior, where cormorant numbers are smaller, control is occurring at only two of 25 colonies).
While such tactics have been applauded by the general public, they may be counterproductive. Studies have shown that the majority of the cormorant diet in the Great Lakes consist of alewives and round goby, both of which are invasive species. Meanwhile, Wires pointed out, cormorant control does nothing to address the more serious ecological issues on the Great Lakes, which range from exotic species to pollution to disease to warming waters.

“To assume that cormorants have a negative impact is wrong,” said Wires. “Cormorants are highly efficient predator but they are pretty much limited by the density of the fish. When fish density becomes more sparse, they’re not going to stick in an area. They’ll move on. And when cormorants fish an area, the fish that remain benefit, with faster growth rates. Also, diseased fish get caught quicker.”

‘Out of control’

Still, the perception that cormorant numbers are “out of control” and “unnatural” remains widespread. In the late 19th century, Wires pointed out, similar attitudes led to the cormorant’s extirpation from much of its original range, as commercial fishermen attacked colonies, trampled eggs, shot birds out of roosts and fed the carcasses to the dogs.

By the mid-20th century, the birds had staged a gradual comeback, only to see their numbers plummet again because of exposure to synthetic pesticides such as DDT.

In 1972, a DDT ban was enacted and cormorants were formally granted federal protection under the Migratory Bird Treaty Act, which set the stage for the bird’s latest comeback. By the 1990s, a rapid expansion of fish farms in the southern states drove further recovery, as wintering cormorants enjoyed the easy pickings from the fish-packed ponds.

It wasn’t long before aquaculture interests were demanding action. Responding to the pressure, in 1998 the Fish and Wildlife Service issued a so-called “depredation order” that authorized the unlimited killing of cormorants at commercial fish farms and hatcheries in 13 states, including Minnesota.

That didn’t stop the flood of complaints and, in 2003, the Wildlife Service issued a public resource depredation order. That rule permitted public agencies and Indian tribes to kill cormorants thought to be affecting a public resource.

While the science behind all the culling has remained murky, that has made little difference in the fate of the cormorants. “Fiction becomes fact, and after a while even biologists start buying into it,” Wires said. “The cormorant lives in an Orwellian universe.”

Mike Mosedale, who has written for City Pages and newspapers in Connecticut, Wisconsin and California, reports on the environment, Indian affairs and other topics.