Loons in Canada and Wisconsin Are Struggling, But Not in New England. Why?
Scientists have different ideas about what’s threatening loon survival in some parts of North America.
The icons of your summer camping trip are in an unusual situation. Loons — the black and white birds with a distinct and eerie two-note call — spend the warmer months of the year in northern U.S. states and across Canada, returning to the same regional pockets every year to breed. And for some reason, Loons living across New England appear to be thriving, while those in Wisconsin and large parts of Canada are not.
“This is the most complicated thing that you could ever imagine to work on. I mean, this is typical of ecology, right?” says Doug Tozer, a scientist with the Canadian Lakes Loon Survey of Birds Canada. “But this one takes the cake.” As ornithologists sort through the range of possible explanations, they’re weighing the pros and cons of particular research decisions and which struggles are due just to poor luck.
A Close Watch Reveals Trouble
Since 1993, a team of scientists have tracked the lives of loons in about 200 lakes in Oneida County, Wisconsin. Led by Walter Piper, a behavioral ecologist at Chapman University and scientist with the National Loon Center Foundation, the group has recorded behavior, weighed individuals and attached small tracking anklets, or bands, to chicks to see how the long-lived birds develop.
The disappearance of the Wisconsin floaters has Piper worried. “I’m a bit of a nervous Nellie, but you know, the numbers speak loudly,” he says. “I think there’s justification for being a nervous Nellie.” The floaters keep a loon cohort hatching as many young as they can. Mating loon couples are territorial, and a given lake only hosts so many pairs. When one in a couple dies or gets too old, a floater moves in to reproduce. Despite the drop in floater loons, the number of mating pairs in Oneida County has stayed steady. Eventually, however, floater numbers could get so low, they can’t fill all vacancies. Piper and his team don’t know where that tipping point lies, though they expect it’s coming. “If they fall behind, as our projections indicate they might, then we will slowly lose the pair on Long Lake and then we’ll lose the pair on Alva Lake,” Piper says — and so on, eliminating breeding pairs over time.
Tozer remembers reading the paper where Piper and his team explained what they were seeing. “That blew my mind when I read that line, because that’s exactly what we see here in Ontario,” he says. During the annual Canadian Lakes Loon Survey, volunteers survey where the majority of North America’s loons live — about 95 percent of the entire population breeds in Canada. If reproduction rates had stayed at 1980s levels, the average loon parents in Ontario would now be having four young over a five-year span. But that’s not what happened: By 2018, that number was down to three. All the while, the number of couples stayed about the same.
Luck Or Lacking Data?
Both Piper and Tozer have ideas about what’s hurting loon survival in their respective populations. When traveling south for the winter, Wisconsin and Canadian loons stop in the Great Lakes, water bodies rife with algae blooms and botulism E outbreaksthat kill fish and birds. In Wisconsin, the if number of fish available per breeding lake are declining, parents would have less to feed their young. Lead fishing sinkers and jigs, which are still legal in the state, kill off loons that ingest them.
Loon-inhabited lakes in Ontario suffer from high acidity and mercury levels. The heavy metal and the contaminants that make acid rain come from fossil fuel combustion and industrial processes like smelting. Acidic waters foster bacteria that chemically modify mercury to make it more toxic — and Tozer and his colleagues found that lakes in the region with more acidic conditions produced fewer loons.
New Englander birds luckily never touch the Great Lakes, for one. Additionally, bird-loving Northeasterners have built loon numbers up by protecting breeding areas, moving couples around and providing artificial nesting areas. About 100 to 150 years ago, people in the region shot loons almost out of existence, Evers says. Different states lost local populations entirely. Recovery programs began in the 1970s have had success, so the vitality of the New England population might just seem stronger because prior numbers were so dismal, Evers suggests.