Study hoping to shed light on cormorant colonies

A study looking at cormorants launched south of the border last year has been expanded northwards this summer to include more bird colonies on the Canadian side of Rainy Lake.
The study originally was looking at the cormorant populations on Lake Kabetogama, said Steve Windels of Voyageurs National Park.

“We wanted to know what they were eating, where they were foraging, and what they were eating in the lake, and we started a banding program with the chicks, as well,” he explained, adding some preliminary work also was done looking at the cormorant colony on the Seven Sisters island chain on the Canadian side of Rainy Lake.
The Ministry of Natural Resources originally supported the project last year with some field assistance for the banding of chicks on the Seven Sisters part of the colony, noted Darryl McLeod of the MNR.
He said the project is a collaborative project between various agencies, including VNP, the MNR, and North Dakota State University.
With the project going into it’s second year, the MNR has expanded the study to include two additional cormorant colonies on the north arm of Rainy Lake, McLeod said.
“For many years, MNR receives concerns from the public and anglers regarding the increasing number of cormorants and what effects they might have on the fish community because they’re fish-eating birds,” he remarked.
“So there’s always those concerns expressed.
“In order to properly address these concerns, it’s always best to base it on real scientific data for these particular colonies, so that’s why we’re encouraged by the opportunity to get this study expanded to Ontario, so we can have some real data to look at in terms of what the potential effects of these birds might be,” McLeod explained.
“Cormorants are sort of a lightning rod for people in the sport-fishing community because basically people view them as a competitor of folks wanting to fish,” agreed Windels, noting this is one of the reasons behind the push for the study—to look into the impact cormorants are having on walleyes and other sport fish.
“Those same questions exist on the Ontario side, as well, folks just want to know,” he stressed.
“Cormorants have increased dramatically since they were almost wiped off the landscape back in the ’50s and ’60s and ’70s, to where they’re much more abundant now, and people see them more,” Windels continued.
“People just have a lot of questions about what’s the role of cormorants and how are they affecting the fishery.”
Understanding the effect which the cormorants have on the fish population means studying the diets of the birds.
Windels explained the study is using the best non-lethal way it can to gather data—going out to the cormorant colonies when the chicks are between one and six-seven weeks old and collecting the food which they have regurgitated.
“And so you can get an idea of what’s being fed to the chicks, which for that period when the chicks are being raised is similar to what the adults will be eating. That’s the best non-lethal way to determine what chicks are eating,” he noted.
Windels said once August rolls around, they’ll have two years’ worth of data for the original colonies they have looked at.
“Cormorants really are opportunistic, really,” he remarked. “They tend to eat what’s most abundant in the lake, and so that’s why it’s nice to have a couple years of data because as the lake changes and different species of fish increase or decrease in abundance, cormorants are kind of going to focus on whatever is easiest to catch.”
McLeod said the study will mean they can see possibly what the differences in diet there may be between the different colonies, and difference in diet composition between years.
It also will give them the opportunity to look at the population characteristics of the nesting
colonies, such as size, and reproductive parameters.
Besides studying the diets of the birds, another part of the project includes banding chicks so that where these birds migrate to throughout their lives can be tracked—such as where they head to when going south for the winter, Windels said.
“This banding program helps to get a picture of how cormorants move about through the whole continent, basically,” he explained.
“There’s lots of biologists around the whole country [U.S.] doing the same thing, so we can pool our data together and get a picture of how cormorants move around, which is important for people that are trying to manage cormorants.
“At the end of the summer, I think we’ll have some interesting data and we will certainly share it with the public as soon as the picture becomes a little bit clearer,” Windels pledged.