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Common Loons are threatened by climate change and pollution

Have you ever heard the haunting, beautiful cry of the Common Loon echoing across a northern lake? It’s a sound that evokes the wild spirit of untouched nature. Climate change is subtly altering Common Loon habitats, and they might not have enough time to adapt. Unfortunately, this majestic bird faces an uncertain future.

Common loons, water clarity and climate change

A new study by Chapman University professor Walter Piper reveals something alarming: declining water clarity is wreaking havoc on Common Loon populations.

These stunning black and white birds, known for their gorgeous plumage and eerie calls, rely on crystal-clear water to hunt for fish, their primary food source.

“Few animals on Earth are at once so beloved and so poorly understood as Common Loons,” says Piper. “This partnership between a loon behaviorist and lake ecologists who collect satellite data on water clarity has given us a unique and powerful window onto foraging efficiency and the loon population as a whole that might help us conserve the species.”

Impact of water clarity on loons

Picture this: a loon gracefully dives underwater, its sleek form disappearing beneath the surface. With its exceptional underwater eyesight, the loon scans the lakebed for the glint of scales – the telltale signs of small fish.

When it spots a target, the chase begins. A successful hunt is essential, especially when loons have hungry chicks demanding food back at the nest.

Cloudy water fundamentally disrupts this process. Imagine the lake floor obscured by suspended silt, algae, or debris.

The loon’s ability to see clearly is drastically reduced. Finding those small fish becomes incredibly difficult. This reduced visibility makes it much harder for loons to provide for their young.

The result? Chicks that receive less food end up with with lower body weights and face a much higher risk of not surviving.

Climate change impact on loons environment

Professor Piper’s research points directly to a concerning culprit: increased rainfall. Over the past two and a half decades, a trend of heavier precipitation (strongly linked to climate change) has emerged.

This isn’t just about a few more rainy days here and there. These heavier rain events act like a giant flush, washing a significant amount of unwanted materials into lakes and waterways. The influx of these materials is what directly reduces water clarity.

How it works isn’t entirely understood yet. It could be:

Dissolved organic matter (DOM)

Rainwater, as it travels over the ground, picks up leaves, soil, decaying plants, and other organic debris. These materials contain natural compounds that, when washed into lakes and rivers, act like a giant teabag.

Over time, they leach into the water, giving it a brownish or yellowish hue. This discoloration reduces light penetration, making it more difficult for loons to see their prey.


Excess rainfall washes various pollutants into waterways. Fertilizers used on lawns and fields contain nutrients that fuel algae blooms, causing a murky green color that obscures visibility.

Moreover, animal waste from pets or livestock contains harmful bacteria and other contaminants that directly reduce water quality.

Faulty septic systems can leak sewage into the environment, introducing harmful bacteria, chemicals, and excess nutrients into the water system.

July climate change: A crucial time for loons

The evidence collected over the past 25 years reveals a disturbing trend. Water clarity in the areas where loons live and raise their young has been consistently decreasing.

Concurrently, scientists have observed a decline in the average weights of both adult loons and, crucially, their chicks. This isn’t a coincidence.

The month of July stands out as a critical period for loon chicks. This is their peak growth stage, demanding a significant amount of food for proper development.

Research has clearly demonstrated that adequate water clarity during this time is a vital factor in whether adult loons can successfully hunt and provide enough fish for their chicks.

When water clarity is poor in July, the ability of loons to meet the needs of their growing chicks suffers significantly.

Wider consequences of climate change beyond loons

Common Loons hold a unique position within their ecosystem, making them sensitive to environmental changes. Because they sit at the top of the aquatic food chain, relying on abundant and healthy fish populations, any disruption to the delicate balance of the system will show up in their health and reproductive success.

The challenges faced by loons don’t affect them in isolation. Declining water clarity, for example, likely impacts a wide variety of aquatic life, from the fish loons eat to the insects and plants those fish rely on.

When we see a decline in loon populations, it’s a red flag, a warning sign that the entire ecosystem might be under stress. Changes in loon numbers can be an early indicator of wider ecological problems that necessitate attention and conservation efforts.

However, Professor Piper isn’t giving up hope. He’s currently establishing a second study on another loon population in Minnesota to see if the same factors are responsible for population declines observed there. This research could unlock the next key step in protecting these beloved birds.

Can we do something to save loons from climate change?

While the science continues, there are things individuals can do to help loons and the lakes they love:

Reduce runoff

  • Eco-friendly lawn care: Opt for natural fertilizers that release nutrients slowly, reducing the risk of excess runoff into waterways during heavy rain. Avoid pesticides and herbicides that can harm aquatic life. Plant native grasses and groundcover that require less water and maintenance.
  • Septic system maintenance: Have your septic system inspected and pumped regularly by a professional. This ensures that the system functions properly, preventing leaks of harmful pollutants that can contaminate water sources.

Less is more

  • Minimize harsh cleaners and chemicals: Many household cleaners contain ingredients that can disrupt aquatic ecosystems when washed down the drain. Look for eco-friendly alternatives or even make your own cleaning solutions using vinegar, baking soda, and natural soaps. This applies indoors and out – think twice before using harsh chemicals to pressure-wash your driveway or deck.

Spread the word

  • Share your knowledge: Talk to your friends, family, and neighbors about the importance of protecting loons and the lakes they inhabit. Explain how individual actions can make a collective difference in safeguarding water quality and the health of these iconic birds.

More about the common loons

As discussed above, Common loons, known for their striking black-and-white plumage and haunting calls, are a fascinating species of waterbird primarily found in North America.

They are symbols of wilderness and are often associated with the pristine lakes of Canada and the northern United States, especially during their breeding season. Here’s a closer look at their diet, behavior, and other interesting traits:


Common loons are skilled hunters, primarily feeding on fish. They dive underwater to catch their prey, using their sharp beaks to grasp fish.

Apart from fish, their diet can include crustaceans, insect larvae, and occasionally small amphibians. Their ability to dive deep (up to 200 feet) allows them to access a wide variety of aquatic life, making them top predators in their aquatic ecosystems.


  • Diving and swimming: Loons are excellent divers, propelling themselves underwater with their powerful legs positioned at the back of their bodies. This anatomical feature, while making them agile swimmers, renders them clumsy on land. They can only take off from water, needing a lengthy “runway” to gain enough speed for flight.
  • Vocalizations: Loons are known for their varied and complex calls, which include wails, yodels, and hoots. Each type of call has specific meanings, ranging from signaling location to expressing distress or defending territory.
  • Breeding and nesting: They are monogamous and return to the same breeding grounds yearly. Nests are built close to the water’s edge, and both parents share duties in incubating the eggs and feeding the chicks.
  • Migration: Common loons migrate to coastal waters in the winter. They shed their striking summer plumage for a duller gray, blending into the winter seascape. The journey is long, and they rely on specific stopover sites to rest and feed.

Fun Facts

  • Loons can live for more than 20 years in the wild.
  • They have solid bones, unlike most birds, which helps them dive deep.
  • The red eyes of the common loon might help with underwater vision, although their exact purpose remains a topic of debate among scientists.

Understanding and protecting the common loon and its habitat is crucial for preserving the biodiversity of North America’s freshwater ecosystems. Their presence and health are indicators of clean, unpolluted water bodies.

The study is published in Ecology.


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