Healthy Thames River Home To Abundance Of Waterfowl

Watermark 14 - Healthy Thames River Home To Abundance Of Waterfowl

The Common Goldeneye is one of the many species of diving duck that overwinters on the Thames River. In recent years, the number of these ducks on the river during winter months has increased.

Once again this winter, the Thames River is hosting a remarkable variety of waterfowl. With ice coverage on the Great Lakes exceeding 80%, ducks, geese, and grebes are migrating inland searching for open water. Several of these birds feed on a variety of aquatic life including: fish, molluscs, crustaceans, larvae, and even aquatic vegetation. For diving ducks and grebes, feeding takes place by diving below the surface and capturing prey with their bills. In order for these diving ducks to be successful, they must be able to reach the bottom to access snails, clams, and crayfish from beneath rocks and logs on the river bed.

Watermark 15 - Healthy Thames River Home To Abundance Of Waterfowl

Of the fifteen species of waterfowl currently overwintering on the Thames River, eight are deemed rare by eBird either by species or location. Redheads are one of the species deemed rare. Each winter we observe more Redheads on the river during winter months. Readheads are a diving duck that feed on aquatic vegetation.

The wide variety of waterfowl that has overwintered on the Thames River the past few years is a good indication of the improved overall health of the river. Since Springbank Dam became non operational in 2008, the Thames River is slowly transforming back to its natural state. The most observable change is the natural reforestation occurring along the river banks. The increased vegetation in this riparian area is preventing bank erosion, and reducing the amount of harmful nutrients and pesticides that enter the river. Bank erosion leads to sedimentation which negatively impacts the health of the river bottom, where many of the tiny vertebrates and invertebrates that these ducks feed on live. High nutrient levels, such as phosphorus, create unhealthy algae blooms which again negatively impact the overall health of the river.

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Each winter Hooded Mergansers can be observed on the Thames River in London, Ontario. These small diving ducks can be observed feeding on small fish and in this case crayfish.

When Springabnk dam was operational, water was held back within the city from late May until early October each year. Damming the river promoted sedimentation, caused nutrients and bacteria to build up, and harmful algae to form. Too much algae is harmful as it reduces water quality and starves other organisms of oxygen. These factors are what led to the unsightly appearance and smell so many Londoners associated with the Thames.

Treated and untreated sewage continues to be released into the Thames River at various location around the city, including Greenway Pollution Control Centre. Human and animal waste increases harmful bacteria levels, such as e-coli, which also negatively impacts the water quality. Allowing the Thames River to flow freely, reduces the build up of this bacteria within our city.

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Another bird deemed rare for our location by eBird is the Greater Scaup. Once again this winter, scaup have been drawn to the open water of the Thames River, and the abundance of aquatic life that is paramount for them surviving the winter months.

By having a free flowing river the past six years, levels of harmful bacteria, nutrients, sediment, and algae have all improved. These improvements are published in the Upper Thames River Conservation Authorities Watershed Report Cards. To some, these benefits are not visible by simply looking at the river. In fact, many Londoners believe the water level appears too low based on the Thames River’s previously unnatural dammed levels.

The improved water quality is evident by the increase and abundance of waterfowl overwintering on the Thames River each year. The improved water quality and reduction in sedimentation has created a much healthier river bottom. As a result, several small organisms that reside on the river bottom are thriving; ones that you and I can’t observe while walking along the river in one of our city parks. This abundant aquatic life is what keeps these many species of waterfowl present on the Thames River throughout the winter months. Without suitable water and an adequate food supply, these ducks would continue their migration to the southern United States or the Atlantic coast.

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This Harlequin Duck is listed as endangered in Canada. Maintaining and improving the health of the Thames River is something we need to take seriously in order for such species to survive. This rare Harlequin Duck is one of the many rare species currently overwintering on the Thames River.

Simply put, wildlife does not lie. The increase, abundance, and variety of all wildlife, not just waterfowl, present on the Thames River indicates a healthy and sustainable river. Water from the Thames River eventually reaches Lake Erie, where London draws a portion of its drinking water from. Keeping the river in its natural state will not only protect endangered species, like the Harlequin Duck, it will help protect the future of our drinking water. The natural reforestation that is occurring along the river banks improves the urban forest, and our air quality as well.

Perhaps we should take more time to observe the nature around us and use it to measure the health of our environment.

Good birding,



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