By Steven Maier
Culling season is coming quickly for a controversial Great Lakes waterfowl after it received a one-year reprieve.
Control of the double-crested cormorant will return this spring when the bird returns from wintering along the Pacific, Atlantic or Gulf coasts, according to federal authorities. Almost all culling was suspended last year after a federal judge ruled in May 2016 that the U.S. Fish and Wildlife Service had failed to adequately assess its impact. With that study complete, the service can again issue permits to kill cormorants to protect property, habitat, airports, fish hatcheries and other birds.
“We’re trying to balance maintaining a stable cormorant population with managing them in the place where they’re causing damage,” said Tom Cooper, a region chief for the service’s Migratory Bird Program.
The agency will issue permits to kill up to 18,270 cormorants this year in eight Midwestern states.
Those applying for a permit must submit photos of cormorant damage, how many cormorants they wish to kill and how they plan to do it, Cooper said.
Once threatened by chemical contamination, the birds have returned in dramatic numbers.
There were only 125 nesting pairs of Great Lakes cormorants in 1972. Today, there are 40,000 pairs, and they’re causing a big problem on many of the region’s islands. Cormorant colonies have degraded many island habitats, forcing other animals to move on.
Anglers know them as the bird whose numbers blew up in the 1980s after tapping into a nearly bottomless supply of the invasive alewife. They’re incredible divers and can eat one-fourth of their weight in fish each day.
And they’re public enemy number one of many perch anglers, although how many perch they eat is hotly debated, Cooper said. Many know them by a distinct calling card–acidic feces that damages cars and buildings. They also destroy vegetation, stripping trees of leaves for their nests and poisoning the ground with their guano.
But activists think of them as the bird that’s faced persecution for centuries and continues to do so despite the protections they received under the Migratory Bird Treaty Act of 1918. Some remember them as an environmentalists’ poster child—their DDT-malformed beaks were displayed on posters. The deformities caused by that insecticide kept them from eating and reproducing, threatening the bird’s existence.
Cormorant management is contentious, Cooper said.
“There’s folks that are on both sides of the issue,” he said.“Our role is to balance those using the best available information.”
The Fish and Wildlife Service began to allow culls in 2003 after complaints mounted of damage done by a booming cormorant population. Cormorants threatening fish hatcheries, vegetation and other birds were often taken without a permit. The birds are either harassed or shot, but many prefer to coat their eggs in oil, asphyxiating the embryos. Cormorant mothers continue to sit on the dead eggs. The mothers otherwise often laid new eggs if they found theirs were smashed.
Cormorant management is often done to protect shorebirds that often live alongside cormorant colonies, but researchers at the University of Minnesota found that the culls hurt some of those same species.
The team analyzed population data forco-nesters from 1976 to 2010 and watched how the colonies fared when cormorants were killed.
Black-crowned night herons nest in the undergrowth, often under cormorant nests, said Francie Cuthbert, one of the co-authors of the study, which appeared in The Journal of Wildlife Management. Culling cormorants should save their habitat from an acidic demise and boost the heron population. Instead, those populations declined when the cormorants were killed.
Egg spraying is probably the culprit, she said. Managers have to traverse the island, causing panicked heron chicks to fall out of their nest. The parents no longer care for them and they die.
For two species of gulls, the opposite is true. The Great Lakes has too many gulls already, and cormorant management makes it worse, Cuthbert said. Gulls raid empty cormorant nests–an easy-access, population-boosting food source.
“When somebody goes in to spray the eggs, the cormorants are the first to take off, and boom, they’re gone,” Cuthbert said. “They’re out sitting on the lake.”
The gulls are quick to take advantage, she said. “They’re into that cormorant colony, busting open eggs as fast as they can.”
That makes for more gulls, and another possible round of eggs from the cormorant mothers, she said.
The team couldn’t measure the effects on the Caspian tern and the American white pelican, two co-nesters of special concern for managers.
The Fish and Wildlife Service is aware of the study, Cooper said. The managers he’s spoken with are open to changing tactics, even if it means hampering efficiency by limiting egg oiling.
There were close to 10,000 cormorant pairs on West Sister Island in Lake Erie before the culling started in 2006, said Jason Lewis, the manager of the Ottawa National Wildlife Refuge in north Ohio. The cormorant colony on the island has since been cut down to 4,000 pairs.
Other nesting species on the island were struggling as the cormorants continued to grow, Lewis said. And West Sister Island is the only habitat of its kind in the western basin of Lake Erie.
“It’s not like these species have any place to go,” he said.
Harassing cormorants only hurts other birds, he said. And they couldn’t oil eggs–the cormorants on West Sister are tree-dwelling. Their go-to tool: a muted .22-caliber rifle, allowing them to shoot birds from afar and limit their disturbance.
Since culling began, the vegetation and co-nesters on the island have bounced back, Lewis said.