Cormorant

Jeff Green | Sep 25, 2008

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Dr.Chip Weseloh

Last Wednesday, The Frontenac Stewardship Council hosted Dr. Chip Weseloh, a specialist in toxicology with the Canadian Wildlife Service, to speak about his studies and observations of double crested cormorants (DCCOs) around the Great Lakes, work that he has been focusing on since 1978.

These birds, which almost made it onto the endangered species list in the 1950s, have bounced back incredibly since the late 1970s.

In recent years cormorants have made headlines in Canada due to a number of government-legislated “cullings” in Ontario, and Quebec, a move that various groups and individuals are either vehemently in support of, or vehemently opposed to.

Cormorant Defenders International (CDI) is an advocacy group that formed specifically to ”respond to the assault on cormorants and to respond to the many erroneous claims made about them”.

In the southern United States, where the cormorants winter, they are being targeted and culled aggressively by anglers, catfish farmers and the government.

In China, fishermen take advantage of the cormorants’ amazing ability to catch fish and have trained them to actually work by their sides.

Dr. Weseloh resides close to the birds he studies. He owns a cottage on Garden Island between Kingston and Wolfe Island and has a blind set up on Snake Island where he and his colleagues continue to observe and research first hand the proliferation of cormorants and their environmental impact.

On Wednesday night, his presentation at the Verona Lions Hall focused on the facts rather than the culling debate.

Due to several factors, including reduced contaminants, increased availability of food, reduced persecution and greater protection, double breasted cormorant populations on the Great Lakes have increased on average by 23.7% per year, from less than 100 pairs in 1973 to over 115,000 pairs in 2007.

On Lake Ontario where the number of breeding pairs went from virtually none in the 1970, there were 30,000 in 2005/06 and there are currently at 22,650 pairs. Eighty-eight percent of the Lake Ontario cormorant population resides on the Canadian side.

In the Kingston area the population is concentrated on Snake, Pigeon and the Brothers Islands where there are currently 4700 pairs, a 17.5% increase since last year.

The effects of these dramatic population increases on the environment include the loss of trees and other herbaceous vegetation due to the birds’ toxic guano. Dr. Weseloh presented a number of slides demonstrating the environmental destruction at the Leslie Street Spit in Toronto, High Bluff Island in Presqu’ile Provincial Park (where a legislated culling took place in 2006) and the Western Brothers Island near Kingston.

Aerial photographs used to observe leaf area indexes, taken over an 11-year period showed that in certain areas, 41% of the tree canopy has been lost.

Another study’s findings demonstrated that Great Blue Herons in Ontario were the bird species most threatened by the cormorants; the combination of heron nest takeovers or abandonments totaled 61.5%.

After the facts had been presented one audience member asked his, “$64,000 question: Are they going to move into the inland lakes?”

Wesleloh's response: “They have already started doing it. MNR is trying to keep track of that using surveys…but yes they have already started moving in.“

Next question. ”So what’s the solution?”

“The most extreme thing is culling and shooting and they tried that at Presqu’ile (Provincial Park) and it certainly worked at the time. It reduced the numbers from 12,000 pairs to about 4000 pairs in 2 years, partly from shooting and partly from the birds leaving to go elsewhere. But that [shooting] is really offensive to a lot of people.”

Weseloh mentioned other alternatives, one being the oiling of the birds’ eggs with vegetable oil, which cuts off the air supply to the embryo. This technique was used at Presqu’ile Park prior to shooting but Weseloh admitted that the disadvantage is that it is “too slow… The managers don’t want to have to wait 4 or 5 years to have natural mortality take place.”

One audience member mentioned seeing a lone cormorant on his dock at Knowlton Lake north of Sydenham and asked what that means.

“It could mean nothing but that cormorants are great scouters. If you were to see a dozen in a tree, day after day in August, they might indeed reappear next year to nest. If this were to happen, you’d be best to harass them daily to keep them from nesting." He stressed that discouraging them as early as you can is the best possible approach.

“Why are there so prolific?” another audience member asked.

“The bottom line is: if there weren’t enough fish for them, they wouldn’t be so prolific.” Weseloh continued, “There must be an abundance of fish out there still after all these years for the birds to reproduce the way they do.”

While cormorants do eat mostly slow, shallow swimming fish of the invasive species, they also eat a small percentage (5%) of small mouth bass and perch.

Weseloh added, “The public outcry of cormorants eating fish is sometimes so strong that it persuades the politicians to dictate what we’re going to do in response to public demands.”

“What’s their benefit?” Weseloh gets asked this question frequently and responded, “What benefit are robins and chickadees?”

Weseloh explained that non-harvested birds that have no economic value still have their place in the environment and in ecosystems. Cormorants and other non-edible bird species must serve other purposes that are not so easy to pinpoint. He suggested that one of the cormant’s purposes might be to trim off populations of slow swimming and sick fish.

Weseloh originally intended to study the DCCO's population explosion without human interference, hoping to eventually see “a crash”, a natural leveling off of the numbers due to food availability.

He explained that while this natural leveling off tends be happening currently on Lake Huron as a result of food shortage, the populations have leveled off in the eastern and central basins of Lake Ontario in recent years only as a result of management and culling.

Weseloh thinks that some of the diseases that are now being found across Lake Ontario might start controlling the populations here but added, “ that hasn’t happened yet in the western basin of lake Ontario.”

While cormorant populations on Lake Ontario continue to grow there is no doubt that the culling debate revolving around them will continue to rage on.