Is the Canadian loon population in danger?

A common loon swimming with her loon chick Photo by Shutterstock/Brian Lasenby

You’re sitting on the dock with an early morning mug of fresh brewed coffee. Or perhaps you’re still nestled in your bed after a late bonfire night, only to be unapologetically interrupted by the resonance of morning – the loon.

To many cottagers, the loon is a sacred part of the cottage experience itself. If you grow up at the cottage, you’re growing up memorizing the sound of the loon. And if you’re new to the cottage, hearing a loon is only an essential part of the ambience.

But maybe you’ve noticed that the loon’s voice is not being heard as much. Maybe you think you’ve also been seeing fewer of them. This is all very possible.

According to the Canadian Lakes Loon Survey, a project of Bird Studies Canada, the number of young loons has been decreasing.

Though there is no proven answer as to why this may be the case, dedicated scientists and volunteers have been collecting data over the years, to gather the most recent loon trends in Canadian lakes, hoping to understand why.  

According to CLLS’s last detailed report, loons produce well in water with higher pH levels and lower methylmercury. This is why smaller lakes in Eastern Canada tend to see lower common loon reproductive success.

What is reproductive success?

In this case, reproductive success is measured by looking at the number of six-week-old loons produced per pair each year. This is because six-week-old loons are about 70 per cent of the adult size and have a much lower chance of being eaten by a predator.

“If the chicks make it to be six weeks old, they’re likely to survive and fledge from the lake that fall,” explains Kathy Jones, the Ontario programs volunteer coordinator for Bird Studies Canada’s CLLS.

These smaller lakes can also receive more acid precipitation and hold fewer substances that help neutralize acids compared to the larger lakes. This means that smaller lakes generally have lower pH levels, which explains why mercury levels could be higher.

Though the CLLS only produces one detailed report every decade, the survey still maintains mini seasonal trend reports throughout the year.

The most recent trends report provided to participants within the spring 2018 season suggests that though the loon population is still above the required number in order to sustain a stable population, that number is actually decreasing, specifically in reproductive success.

According to the spring report, the estimated number of six-week-old chicks per pair has been fluctuating drastically since the early ’90s. In 1991, there were approximately 0.76 chicks who survived, while in 2017, that number dropped to around 0.55 chicks. Jones explains that as long as the number of chicks remains above 0.48, then the number of territorial breeders is unlikely to decline, making for a stable population.

Seeing a decrease in the number of chicks who survive to six weeks, however, is a huge red flag, says Jones.

Typically, loons tend to do well on healthy lakes, so the questions that come up are: What does this say about our lakes? And what does this mean for other, more vulnerable species?

Loons and our lakes

According to CLLS’s 2012 report, the common loon is a powerful indicator of lake health, especially in relation to mercury pollution and acid precipitation. This is because loons hold a high position in the food chain. So, every time an animal eats another one, pollutants, if present, can build up, a process called biomagnification. And once these pollutants reach the loons, they are at their highest concentrations.

Similarly, acids and the toxic metals they mobilize, interfere with fish gill functions, which reduces fish growth, reproduction, and survivorship, ultimately lowering fish abundance in the more acidic lakes. This means less food for the loon chicks and their parents.

But how does mercury actually affect the loons?

Adult loons with higher mercury levels tend to be slower. They spend less time doing energy-required activities, including gathering food for their chicks and defending breeding territories. This suggests that lakes with higher levels of mercury see a lower reproductive success rate, as the adult loons become lazy parents and have a higher likelihood of neglecting to feed and protect their babies.

Though the rate in reproductive success has been declining over the years, Jones explains how we would have to have a huge drop in the number of birds in order to see them become endangered or extinct. She says, though, that “it’s important to keep our common birds, common to our environment.”

So, in the meantime, here’s what we can do to help these birds:

Make shorelines safer

Let native wetland plants grow along your shoreline. Natural waterfronts provide shelter and food for both fish and loons.

Slow down
When approaching the shore, slow down and keep your wake to a minimum as wakes can wash out nests or separate young chicks from their parents.

Dispose properly

Take trash and fishing line to shore for proper disposal. Garbage can injure birds, and food scraps could attract larger predators.

Keep lakes clean

Reduce your impact by using less electricity and fewer fossil fuels, and do not add pollutants, such as hazardous wastes, to our rivers and lakes.

Get involved

Participate in loon or lake monitoring by joining the Canadian Lakes Loon Survey.

If you are interested in helping loons while monitoring their environments, visit birdscanada.org/loons and become a participant for the 2019 survey season.

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