Via Community News Service, a University of Vermont journalism internship
Nearly 40 years ago, the common loon was not so common. The birds were placed on the Vermont state endangered species list after shoreline development and poisonings from leaded fishing tackle drove their numbers down to just a handful of nesting pairs.
Today, the state’s population has grown to 117 pairs and the birds are no longer endangered, due in part to dedicated conservation efforts.
Even so, loons continue to face similar threats. Wake boats produce large waves that disturb loons’ nests and reduce water clarity, and more frequent rainstorms make their habitats less hospitable. And, despite a ban on some lead fishing tackle, loons are still dying from lead poisoning.
Scientists at the Vermont Center for Ecostudies and Vermont Fish and Wildlife have a long-standing Loon Conservation Project that continues to monitor the loon population and educate the public about what human behavior puts loons at risk. They urge people to avoid leaded fishing tackle and to steer clear of inland areas when on a wake boat.
“Give them space; our birds are fairly tolerant,” said Eric Hanson, the center’s loon biologist.
A persistent threat
In 2007, Vermont banned the use of lead sinkers that weigh a half-ounce or less. But data shows that lead poisoning has killed more Vermont loons in the past four years than in the previous four.
It may seem that conservation efforts are falling short, but Hanson says the increase in lead-related mortality actually reflects Vermont’s thriving loon population.
“When loons were in trouble 50 years ago … that was a combination of fishing gear, disturbance to nest sites, flooding of nest sites on reservoirs, lack of habitat,” Hanson said.
Now the loon population has bounced back. As the birds occupy more lakes, issues with anglers, territorial disputes and ingesting leaded fishing tackle have increased. But unlike larger conservation issues caused by climate change, leaded fishing gear is one threat Vermonters have the opportunity to reduce immediately.
Because loons lack teeth, they swallow their prey whole, grinding up fish bones and other tough food with the pebbles found at the bottom of the lake. While diving, loons often swallow lead sinkers, causing fatal lead poisoning.
Between 2016 and 2020, the center counted five loons that died of lead poisoning out of 40 total mortalities. Between 2021 and 2025, that number doubled, and overall mortalities also increased to 70. But the overall percentage of lead-related loon deaths have increased by less than 2 percent points over the same time span, Hanson’s data shows.
Hanson suspects that the increase is partially due to there being more loons. This trend is also reflected in non lead-related deaths. From 2016-2020, the center tallied only two loons deaths caused by non-leaded fishing gear compared to 10 from 2021-2025. Trauma deaths due to other loons also increased from four to 12.
Hanson said it’s unclear if the recent lead deaths are caused mostly by illegal sinkers or by legal leaded tackle, such as jigs. He estimates roughly half and half, but the lead pieces still need to be weighed and analyzed. It is also hard to know the exact type of lead, as it can dissolve in the loon’s gizzard.
Post-mortem procedures called necropsies help scientists learn more about the loons’ condition and causes of death. They’re especially helpful for lead cases, as the effects of lead are typically invisible from the outside.
One loon necropsied by the team last year had died after being attacked by another loon. Researchers also found lead in its bloodstream. But they concluded that the poison had only weakened, not killed, the bird, which made it more susceptible to the fatal attack.
In other cases, scientists can intervene and save birds from lead poisoning. Two years ago the center had been tracking a seemingly weak bird. Hanson jumped out of his canoe and grabbed it, bringing it to the lab for tests.
Scientists found high levels of lead in its bloodstream but no lead object. They administered a medicine to do chelation therapy on the bird, a chemical process that binds with the lead and flushes out the toxins. The loon regained its strength and was eventually released into Lake Morey.
Vermonters also play an important role protecting loons from lead. Last year, the center and Vermont Fish & Wildlife started the Fish Lead Free Project, which places collection tubes at over 30 bodies of water with boat access. The tubes are for anglers to discard leaded sinkers, along with other unwanted fishing gear. At times, plastic bags full of lead will be stuffed in the tubes, but mostly they’re full of discarded fishing line.
“It’s kind of a hit or miss what we’re finding,” Hanson said.
The collection tubes feature information on how lead affects loons, but the text is small and difficult to read, Hanson said, noting, “You have to take curiosity to read it.”
The center also published a comic strip to raise awareness about the loon deaths. “Something is Killing Our Loons,” has multiple panels detailing how lead affects loons, the laws that are in place, and what people can do to help. Sammi Rizzo, who interned at the center, created the comic after attending a loon necropsy where they saw firsthand how lead attacks a bird’s organs.
“It’s all green and gross inside because of the way the lead reacts with the mucus inside of the gizzard,” they said.
Rizzo believes lead is one of the rare issues in conservation where there is a direct solution. “Here is this one concrete thing: lead tackle that is causing the issue,” they said.
Hanson agrees.
“We’ll try to keep those collection tubes going forever and just keep reminding people, ‘Hey, you can make a difference by doing this,’” he said.
Rough waters
Loons depend on clear water to find their food. This makes them especially vulnerable to increases in turbidity — the cloudiness of water caused by suspended sediment and other particles.
Turbidity levels in Vermont’s lakes have been increasing over time due to large rain events and water disturbances, such as the use of wake boats. Scientists have found that when turbidity is higher, adult loons struggle to feed themselves and their young, leading to declining survival rates. While some of the factors contributing to turbidity are large scale environmental problems, wake boats are one source of disturbance that can be managed.
Wake boats are designed to displace large volumes of water, creating large waves for wake surfing and other sports. According to Hanson, those waves can threaten loons in two ways: by stirring up sediment in shallow water and by flooding nests that are typically built between 2 and 8 inches above the shoreline.
“It doesn’t take much to flood a nest from a wave,” Hanson said.
Because loons nest during the same summer months when wake boat activity is at its highest, their eggs are vulnerable to repeated waves and disturbance.
On June 11, Vermont enacted a law that substantially limits where the boats can operate on many of the state’s lakes. The law says wake boats must stay 500 feet from any loon nesting areas that are marked with a sign between May 1 and July 31.
“Fewer chicks are surviving. And fewer of those chicks are coming back as 4- or 5-year-olds. They’re weak. They’re not getting enough food,” Hanson said.
More extreme weather is also creating muckier waters for loons.
Travis Sheldon, director of water quality and operations at the Champlain Water District, said rainstorms that cause spikes in turbidity have become both more intense and longer-lasting in recent years, with elevated turbidity sometimes persisting for several weeks after major storms.
The Champlain Water District has historically measured low levels of cloudiness at its intake, about 75 feet below the lake’s surface. But in recent years, Sheldon said major storms have occasionally doubled or even tripled those readings, making the water significantly murkier.
“[I’m concerned about] the intensity of each of the turbidity spikes that we tend to see now, and the trend that they seem to be happening more frequently as well,” Sheldon said.
Hanson, too, spoke to the challenges posed by turbid waters.
“We’ve had some extreme cases in Vermont after flood events,” he said. “We had a chick that was starving that we rehabbed and another that died because its parents left after not being able to see in the water.”
Sheldon added that he has not seen data directly connecting wake boat activity to measurable water-quality changes at the district’s intake. But he said moving wake sports into deeper water reduces the amount of sediment that can be stirred up.
“We’re just adding another stressor if our lakes become more turbid,” Hanson said.
Although Vermont’s adult loon population remains stable, Hanson said protecting breeding loons is essential to maintaining their recovery.