The mostly bird-free skies above Lake Huron's Thunder Bay during the recent Brown Trout Festival were a welcome sight to anglers who have spent years competing — often unfavorably — with double-crested cormorants for their catch.
Federal and state agencies have waged war in recent years against the large, black waterfowl notable for their orange facial skin and hooked bills. Cormorants can dive up to 25 feet deep and stay under water more than a minute, gorging on yellow perch, bass and other species. Fish farmers in the Mississippi Delta say they devour $5 million worth of catfish fingerlings a year.
Ironically, cormorants were endangered in much of North America a few decades ago. Now they're so abundant — and destructive — that wildlife managers have blasted tens of thousands with shotguns, destroyed nests and covered eggs with oil to smother developing chicks.
The campaign is getting results, at least in some places. Cormorants haven't disappeared from Thunder Bay, but charter boat skippers say the days when gigantic flocks hovered like storm clouds are mostly over.
The perch fishery that crashed a decade ago near the Les Cheneaux island chain at Lake Huron's tip has rebounded since cormorant numbers there were reduced by 90 percent, said Dave Fielder, a Michigan Department of Natural Resources biologist.
The Great Lakes cormorant population, one of North America's largest, has steadied at about 230,000 after rising exponentially since the 1970s. Continentwide, it's estimated at 2 million.
Yet debate still rages over the effectiveness and morality of lethal control, which has been tried in 16 states and a few sites in Canada.
Critics say cormorant growth was showing signs of leveling off before the killing began, suggesting the birds were reaching their natural capacity. They say the cull does more to chase them elsewhere than reduce numbers.
"You're making people in a few areas feel better, but no one really knows what the overall effect is," said Linda Wires, a University of Minnesota waterfowl researcher who helps conduct a biennial census of Great Lakes cormorants.
It's also inhumane, said Liz White, director of the Animal Alliance in Canada. Many birds wounded by gunfire dangle painfully from nests or branches until they die, she said.
"It's a pretty miserable thing to watch," White said.
Cormorants get little sympathy in Alpena, where sport fishermen at the Brown Trout Festival likened them to a biblical plague.
"You can't stand a chance against them," said Rick Konecke, a charter captain. "They're eating machines."
Large cormorant colonies compete with other waterbirds for food and habitat. On some islands, they ravage trees by breaking branches and stripping foliage for nests. Their highly acidic excrement alters soil chemistry.
Some 20,000 have overrun Middle Island in Lake Erie, reducing the canopy — the upper layer of trees — by 40 percent and endangering some of the Great Lakes region's rarest vegetation.
"If we don't try to control the cormorants, we are going to lose a valuable ecosystem," said Aaron Fisk, a researcher at the University of Windsor in Ontario, who studies effects on island soil.
Sympathizers say cormorants have their place in nature and the damage they cause is exaggerated.
They've nested on just 260 of 30,000 Great Lakes islands, Wires said, and there's little hard evidence they have taken a significant bite out of fish stocks. Invasive species, pollution and overfishing cause more harm, but cormorants "make an easy and targetable scapegoat," she said.
Cormorants once were threatened by DDT, the pesticide that also nearly wiped out the bald eagle. The Great Lakes population stood at just 230 in 1972, but exploded after the chemical was banned. In the South, their winter refuge, an aquaculture boom created a magnet for hungry flocks.
"There's no precedent I can think of for a species that was in so much trouble to be doing this well so quickly," said Pete Butchko, Michigan director of the U.S. Department of Agriculture's wildlife services program, which handles the culling operation. "It's just stunning."
Federal officials in 1998 allowed fish farmers in 13 states to shoot cormorants. Five years later, the government authorized lethal control in 24 Southern and Great Lakes states.
More than 73,000 cormorants have been shot under the 2003 order. Eggs in about 70,000 nests have been oiled, and 13,000 nests have been destroyed.
Supporters of the cull acknowledge it's unclear whether the aggressive response will succeed in the long run. Thus far, it's just thinned out cormorants in overpopulated spots. Biologists are debating whether to try managing them across entire regions or migratory flyways.
"If you're controlling them on one site and think your problem is solved, you're going to be surprised," said Mark Ridgway, a biologist with the Ontario Ministry of Natural Resources.