Victim or Perpetrator?
Rescuing a species from extinction doesn't
always have a happy ending.
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| Double-crested cormorants are colony nesters, often with hundreds of even thousands of pairs nesting on a single island. |
Wildlife conservation efforts across the globe have rescued many species from the brink of extinction. The bald eagle once faced seemingly certain demise, but is now a common sight around the nation. Their successful return, as well as that of other wildlife, has been widely celebrated and seen as a sign of a healthier environment.
But when a species rebounds too much or too quickly, not everyone celebrates. Another fish-eating bird that has made a significant rebound is the double-crested cormorant, a large, dark-colored waterbird with a hooked bill and long neck and tail. The cormorant’s comeback is a perfect example of a success that some believe has gone too well, and of how public perception of a species can quickly shift from victim to perpetrator.
Cormorants, the Victim
Like many other fish-eating birds, cormorants fell victim to commercial pesticides and contaminants—most notably DDT and PCBs in the 1950s through the early 1970s. These chemicals thinned the birds’ egg shells, making them fragile. They also prompted deformities like crossed bills and clubbed feet. The cormorant population plummeted. By 1973 only about 125 breeding pairs of cormorants remained throughout the entire Great Lakes region, according to Canadian authorities.
Fortunately, change was on the horizon. The U.S. Environmental Protection Agency banned the commercial use of DDT in 1972 and PCBs in 1978. Cormorants received additional protection in the 1970s when they were added to the list of species covered by the Migratory Bird Treaty Act of 1918 and to several states’ list of threatened and endangered species. Following the path of eagles and osprey, cormorant numbers began to rebound.
The bird’s initial success was celebrated by most, said D.V. Chip Weseloh, who monitored cormorant contaminant levels and population trends for years as adviser of wildlife toxicology for the Canadian Wildlife Service in Ontario. “Within eight years they were showing signs of increase and within 10 years they were coming back with a vengeance. In the early 1980s, the recovery was the best news going,” he said.
But as populations increased into the 1990s, public concerns and suspicions over the bird’s impacts to recreational fisheries, vegetation and other waterbirds also increased. “Public perception had changed immensely,” Weseloh said.
It wasn’t long before the victim became a perpetrator.
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| A researcher at Cornell University holds a cormorant that has been fitted with a radio-tracking device to study the bird's migration patterns. |
Cormorants, the Perpetrator
The bird’s biology, behavior and appearance influences its poor reputation, said Shauna Hanisch of the U.S. Fish and Wildlife Service’s Division of Migratory Bird Management. On the other hand, she doesn’t think the “bad rap” they get is entirely unjustified.
“It’s clear that superabundant birds are nearly always seen by humans as a nuisance,” she said. “And, to be fair, they are often a source of real economic or human health damage.”
One of the initial cases of economic damage came from problems cormorants caused for catfish farmers in southern states like Mississippi, Alabama and Arkansas, according to Pete Butchko, director of U.S. Department of Agriculture’s Wildlife Services (USDA-WS) in Michigan.
“Our agency’s initial involvement with cormorants actually came with protecting aquaculture in the South,” he said.
According to the federal agency, cormorants cause millions of dollars worth of damage to the aquaculture industry. In Mississippi, the birds consume an estimated $3 million of commercially reared catfish annually, while millions more are spent to prevent damage.
It wasn’t long before the agency’s attention shifted to Michigan and the Great Lakes, as effects of cormorants on fisheries and vegetation were assessed.
Cormorants are colonial nesters, sometimes with thousands of nesting pairs on a single island. Large concentrations of the birds and their nitrogen-rich droppings can have a “considerable impact on the vegetation,” Weseloh said.
This has caused concern among park officials in Canada and the U.S. They worry that cormorants will strip park islands of vegetation, decreasing aesthetic value. Other studies indicated that cormorants may indirectly impact other species of island-nesting birds, like the black-crowned night heron, by destroying nesting habitats.
Perhaps the most controversial issue has been the question of whether the birds impact commercial or recreational fisheries. According to Weseloh, this is the most difficult risk to assess, partly because Great Lakes fish populations are tough to estimate.
What is known is that cormorants consume about a quarter of their body weight in mostly noncommercial species daily. Some fishermen are concerned that the cormorant’s impact on forage fish numbers is affecting larger, game fish that feed on them.
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| Cormorants in the water, sometimes with only their neck visible above the surface. |
“With the depletion of the cormorant’s primary food source, they have started to target perch, bass and salmon in some areas,” said Norm Anderson, president of the Flint River Valley Steelheaders, a Great Lakes sport fishing organization in Michigan.
“We’re not out to eliminate them. That’s not our intention. Cormorants are a native species to the Great Lakes,” Anderson said. “We want a manageable control.”
The Conflict Continues
Fish and wildlife managers from agencies in both the U.S. and Canada have responded with an assortment of management actions. These include lethal activities such as shooting and covering eggs with vegetable oil to prevent them from hatching. Non-lethal actions such as nest disruption and scare-tactics such as pyrotechnics are also used.
These activities are often accompanied by legislation. In 2007, Michigan began requiring the state to manage and control cormorant populations to protect personal property, natural resources and human health and safety. Hanisch confirmed that active cormorant management programs are taking place in at least eleven other states in the Midwest, Northeast and South.
So far, Butchko said his agency’s efforts have been well received in Michigan. “People in affected communities are generally very appreciative,” he said.
Some organizations, like the Flint River Valley Steelheaders, even kick in to help financially support efforts when funding is low.
“We don’t need anyone to say we should get rid of all of the cormorants because we don’t want that. And we don’t want people to take this into their own hands,” Anderson said. “We want to help protect the environment for everyone.”
Other locations have received mixed criticisms, particularly from animal rights activists and bird enthusiasts.
Julie Woodyer, campaign director for Zoocheck Canada and Cormorant Defenders International, believes these management actions are unwarranted, and that the real problem is a “misunderstanding” of the birds.
“Not once have we heard about the positive impacts of cormorants,” she said. “From our perspective, the cormorant’s recovery is a good news story.”
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| Stomach content analysis studies aim to gain a better understanding of the cormorant's diet. |
Many see the cormorant’s return as a sign of a healthier environment and bird watchers are often drawn to islands to view cormorant colonies, she said.
Woodyer believes management should refocus its efforts to address other Great Lakes issues like invasive species and diseases like avian botulism.
“We want to see ecosystems evolve naturally,” she said. “And, that includes naturally occurring species, including cormorants.”
Responding to these different voices is one of the challenges of wildlife management, Hanisch said. “There is a line that must be walked that balances responsiveness to the public and responsibility to manage and conserve species.”
Looking to the Future
With increasing human populations and urbanization, interactions and conflicts with wildlife have become commonplace. The double-crested cormorant is only one of many species in the Great Lakes region experiencing this shift from victim to perpetrator.
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| Cormorants, like many other colonial waterbirds, are known for being messy. Their acidic droppings can kill vegetation and "whitewash" the islands on which they nest. |
The gray wolf’s recent comeback in Michigan’s Upper Peninsula and the upper Midwest has ranchers concerned about threats to livestock, residents concerned about public safety and some hunters worried about risks to deer.
Similarly, resident Canada geese and white-tailed deer populations have southern Michigan residents concerned about property damage and deer-vehicle collisions.
It’s clear that human-wildlife conflicts won’t be disappearing anytime soon. But Butchko and others are optimistic that socially acceptable population goals for double-crested cormorants and other species can and will be met and sustained.
“We’ll continue to work with our neighbors to learn more,” he said. “The most important thing we need to remember is that all wildlife, regardless of species, deserves our appreciation and respect.”
Bret A. Muter is a first-year master’s student in the Department of Fisheries and Wildlife. This is his first appearance in EJ. Contact Bret at muterbre@msu.edu
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