Are We Losing the Loons?

What is Happening to Our Loons in Ontario?

The Common Loon (Gavia immer) is Ontario’s provincial bird and a well-known character in cottage country – its mournful wails and uplifting laughter play the song of summer for many who retreat to the wilderness for peace and relaxation. With their striking appearance, magnificent diving skills (watch this if you have you never seen a loon diving underwater) and the way in which they effortless glide across the water’s surface, it is no wonder they are often looked upon with awe. It would be difficult to picture Ontario’s wilderness without them as Ontario currently hosts more than one third of the global population of breeding Common Loons. However, it has become known among scientists that something quite troubling has been happening to the loon population in Ontario for many years now, and it may get worse if we continue on the same way.

A recent study (2020) conducted by Bianchini et al. found that the reproductive success of loons has been on a consistent decline in Ontario. (The decline is by 0.10 six-week-old young per pair per year. The data includes 38 years of observations from over 1500 lakes that were monitored by citizen scientists since 1981 as part of the Canadian Lakes Loon Survey, a program run by Birds Canada.) By carefully analyzing long-term reproductive data in conjunction with long-term lake health data, scientists have confirmed that the cause of the decline can be linked to two major factors – acid rain and mercury. Other factors related to human-born disturbances including noise and habitat loss are also leading to decreases. But before we delve into how these factors it is important to understand a little bit about the loon lifecycle.

A Little Bit About Loons

Loons are long-lived species, living up to 30 years in the wild. They typically mate for life, however, some studies say it is for 20 years and therefore some loons may have 2 mates in their lifetime. They like to return to the same breeding grounds in the early spring right after ice-break and will often reoccupy the same lake and nesting area year after year to raise their young. Loons are excellent swimmers but do not fair well on land so they build their nests very close to the water’s edge, often along the shoreline in mats of reeds, mud and sticks where they can hide from mammalian predators on land. Once the young hatch in late June, they can swim virtually immediately but sometimes rest on their parents’ backs to conserve heat and hide from predators such as large fish. After 11-12 weeks, the chicks start diving for their own food, and by the time they are adults, they feed almost exclusively on fish from the lake, diving up to 80 m deep to catch their prey. As with other migratory birds, loons also take off in the fall and head further south to the Gulf of Mexico or towards the east or west coasts of North America for the winter.

As top predators on the lake food chain, loons are highly connected to other animals in a lake ecosystem. For example, when a loon eats a fish it is not just connected to that fish, but also all the food which that fish ate, plus all the food which the fish’s prey ate and so on all the way down the ladder. As such, each time an animal eats another animal, pollutants and contaminants can gather in greater concentrations inside the feeding animal – this concept is called biomagnification. Top predators are highly susceptible to biomagnification because they are at the end of the chain and have consecutively consumed large amounts of pollutants from the organisms below them on the food chain. So how does this all relate to acid rain, mercury and declines in loon reproduction?

Likely Causes of Decline in Loon Reproduction Rates

Sulfur oxides from acid rain help feed sulphate-reducing bacteria in lake ecosystems, which then convert mercury into a more bioavailable form, known as methylmercury, for uptake by animals. This process becomes more rapid as climate change increases the frequency and severity of flooding and precipitation events. As a result, lakes that have been exposed to acid rain but are not large enough or do not have enough nutrients, such as calcium, to buffer the acid will turn more acidic. This leads to more methylmercury production, the contamination of aquatic organisms such as fish, and the subsequent contamination of birds, such as loons, who eat the fish. Mercury compromises the immune system and behaviour, making loons spend less time hunting for fish and chicks more susceptible to predators. The acidification of lakes also negatively affects the size of fish populations and the level of biodiversity, leaving less food for loons and their young. Essentially, acidic lakes lead to the contamination of fish and other organisms with mercury, causing declines in these species and cascading effects up the food chain to loons.

Even though air pollution levels (sulfur dioxide) have declined in recent years, many lakes have been slow to recover and thus remain acidic due to little buffering capacity. Climate change only worsens this scenario by warming our lakes and preventing cold water-loving fish species (a food source for loons) from re-establishing. Droughts are also becoming more common and further contribute to the acidification of lakes and the production of methylmercury by re-exposing sulfur in sediments and wetlands. In addition, changes in temperature and precipitation have caused an increase in black fly abundance in the spring which torment chicks and can lead to nest abandonment. Droughts and flooding have also made nest sites inaccessible in some areas. In conclusion, sulfur oxides from acid rain, in combination with multiple climate change stressors, have led to an increase in methylmercury levels in lakes, resulting in lower reproductive rates for Ontario loons.

But acid rain, mercury and climate change are not the only problems. Shoreline development has been cited as a large threat to loons who rely on healthy, vegetated shorelines for nesting and raising their young. Studies have shown that hatchling success decreases as cottage prevalence increases, mainly because disturbed shorelines remove nesting habitat and make loons more vulnerable to predators. Boating can also result in collisions and direct loon mortality, as well as nest abandonment due to disturbance. Finally, excessive noise and at key times during after nesting season can also lead to nest-abandonment.

Although the Common Loon population is relatively stable in Canada, compared with species that are listed at risk, the decline in their reproductive success in Ontario means a steady decline in their population size over years (Tozer et al., 2013). It is also predicted that there will be a 56% loss in their current breeding range by 2080 as loons head north to evade the effects of climate change (National Audubon Society, 2015).

The Decline in Loons Means So Much More

Reproductive success of loons is used as a bioindicator for how healthy lake ecosystems are since loons are at the top of the food chain and rely on a plethora of organisms lower on the food chain. Healthy food webs are needed to successful fledge chicks, therefore declining loon reproduction rates also correspond to declining lake health.

Nesting loon at the shore. Photo: Jody Parks on Pixabay

How Can You Help the Loon?

A major portion, if not all, of the projected losses of the loon population can be avoided if we take action now. There are many simple steps that the average person can do to support the conservation of loons and restoration of their habitats right in our own backyards!

Do your best to prevent acid rain. The acidic part of rain comes from sulfur dioxide and mono-nitrogen oxides which get released into the atmosphere from burning fossil fuels. You can reduce the level of these gases in the atmosphere by opting for more eco-friendly choices such as reducing your gas emissions (carpool, ride your bike or walk where possible instead of driving, paddle your boat when you want to cruise across a lake), saving energy (using energy-efficient appliances and turning off lights and electronics when not in use), or opting for green technologies (solar, wind, and water). You can also support the research of alternative energy sources by donating to energy organizations and charities.
Participate in monitoring loon populations and become a lake steward. Becoming a citizen scientist is extremely valuable to the work that scientists do – it allows them to learn much more about loon populations on a much larger scale than what would be feasibly possible using just their own resources. You can become a steward on your own lake to advocate for better boating, fishing and shoreline practices at the same time as monitoring loon populations by signing up to be a participant of the Canadian Lakes Loon Survey.
Be mindful of boating and fishing practices. There have been many reports of loons being killed from colliding with boat motors, especially because loons are diving birds and are therefore more difficult to locate when travelling on the water at fast speeds. If you know there are loons on your lake, do your best to keep your eye out and reduce your speed. Try to avoid areas where you know loons frequent. Large boat wakes can also damage a loon’s nest along the shoreline and dislodge eggs from nests, causing them to be lost in the lake. Reducing your boating speed to under 10 km/h within 30 m of the shoreline can mitigate these risks to loons. In addition, ensure your unwanted tackle, fishing line and plastics are disposed of correctly to avoid loons and other animals such as turtles from becoming entangled and injured.
Restore your lakefront property. Loons depend on shorelands for nesting opportunities. These areas must be relatively free from human disturbance and should be well-vegetated to provide refuge from predators. Leaving fallen logs in place will also encourage fish (food for loons) to inhabit the area, as well as provide a base for a potential nest. Need help deciding how to restore your shoreland? You can attend a Design Your Own Shoreline Garden workshop or contact us for a site visit. We can help you with a habitat stewardship plan to identify options for loon conservation.
Keep the trees and shrubs. Natural vegetation within shorelands, and including downed or dead trees, shrubs and even leaves, contribute to calcium levels in lakes. Calcium helps buffer against acidification from acid rain, which in turn helps reduce mercury levels and ensures the base of the food chain in the lake is healthy. Natural vegetation at the shore especially also provides habitat for loons and other declining wildlife such as skinks, salamanders, and songbirds.
Limit use of fireworks. Loons, like many other wildlife species, are frightened by loud erratic noise, which may lead them to abandon nests and offspring. Silent fireworks are available for sale in the UK- and can be purchased online. Use laser light shows to celebrate events. Alternately choose to celebrate in more developed areas such as community parks. Finally, wildlife is not as vulnerable at certain times of year- especially in the winter.

Article by Angela Vander Eyken

Sources:

Bianchini, T., Tozer, D., Alvo, R., Bhavsar, S., & Mallory, M. (2020). Drivers of declines in common loon (Gavia immer) productivity in Ontario, Canada. The Science of the Total Environment, 738, 139724–139724. https://doi.org/10.1016/j.scitotenv.2020.139724

Evers, D.C., Paruk, J.D., McIntyre, J.W., & Barr, J.F. (2020). Common Loon (Gavia immer). https://birdsoftheworld.org/bow/species/comloo/cur/introduction

Heimberger, E. (1983). The Impact of Cottage Development on Common loon Reproductive Success in Central Ontario. The Wilson Bulletin (Wilson Ornithological Society), 95(3), 431–439.

National Audubon Society. (2015). Audubon’s Birds and Climate Change Report. http://climate.audubon.org/sites/default/files/Audubon-Birds-Climate-Report-v1.2.pdf

Nature Canada. (2015). How much do you know about the Common Loon? https://naturecanada.ca/news/blog/how-much-do-you-know-about-the-common-loon/

Tozer, D. C., C. M. Falconer, and D. S. Badzinski. 2013. The Canadian Lakes Loon Survey 1981-2012: 32 years of monitoring Common Loons as indicators of ecosystem health. Published by Bird Studies Canada. 14 pp. https://www.birdscanada.org/wp-content/uploads/2020/02/CLLSsummary.pdf

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