LAKE VERMILION— It appears common loon numbers dipped this year on the east end of Lake Vermilion, based on results from the latest loon count. The Vermilion Lake Association, and its predecessor Lake Vermilion Sportsmen’s Club, has been conducting the annual count with dozens of volunteers for the past 36 years.
A total of 71 counters found 195 loons on the lake during this year’s count, conducted on July 15. That included 159 adults and a total of 36 chicks.
Those numbers represent a 17-percent decline over last year’s tally and are the first time that the number of loons counted fell below 200 since 1992, when volunteers counted 184 loons.
“I was surprised,” said Claire Zweig, who coordinates the count for the lake association. “It was a good day for counting. You could see them clearly.”
Loon numbers on the lake’s west end appeared stable, while the lake’s east end saw a 28-percent drop— from 143 loons last year to 104 in 2019. Wildlife surveys always include some level of variability, so a single year’s numbers don’t necessarily suggest a declining population. It would take a few more years of similar data to draw such a conclusion.
This year’s numbers, however, represent the third straight year that the loon tally has come in below the ten-year average count of 238 loons. Volunteers sighted 202 loons in 2017 and tallied 235 loons last year, before this year’s substantial dip.
Minnesota is home to more common loons than all other states in the U.S. combined, except Alaska. And as the state bird, interest has long been high in this iconic resident of the state. In the wake of the 2010 BP oil spill in the Gulf of Mexico, researchers have been closely watching loon numbers for signs that the incident on the Gulf could be impacting loon numbers and reproduction. Previous research has demonstrated that loons in Minnesota and Michigan were exposed to the 2010 spill, but it remains uncertain how quickly any effects from that exposure might show up in population trends and reproductive success. The Lake Vermilion loon count is one of the longest-running loon counts in Minnesota, which makes it particularly valuable for researchers watching the long-term health of the state’s loon population.
Most Minnesota loons winter on the Gulf Coast, so they likely were exposed to some of the toxic byproducts of the 2010 spill. In addition, young loons from the region will frequently spend their first several years living on the Gulf. They don’t return to breeding grounds on northern Minnesota lakes until they reach maturity. Zweig said she has no idea if this year’s numbers suggest that Lake Vermilion is finally feeling the effects of the oil spill. She said she hears plenty of speculation about the lake’s loon population. “I’ve kind of given up on theories,” she said. On the plus side, Zweig noted that she has yet to receive any reports of dead loons on the lake this year.
Loons are good indicators of water quality because they need clean, clear water to catch food. They are also sensitive to disturbances such as lakeshore development and contaminants like mercury and lead in their environment.