Cormorants at Lake St. Clair Metropark: What Visitors Should Know

If you’ve walked the shoreline at Lake St. Clair Metropark and noticed large, matte black or dark brown-black water birds with an orange-yellow throat diving for fish or roosting in the trees on Dog Island, you’ve spotted one of the park’s most talked-about residents: the double-crested cormorant. Here’s what to know about them.

What is a cormorant, exactly?

The double-crested cormorant is a waterbird about the size of a small goose, with a long neck, a hooked bill and dark feathers that can look almost black from a distance. Adults are typically 2.5 to 3 feet long with a wingspan approaching 4.5 feet. They’re excellent swimmers and divers, and you’ll often see them perched with their wings spread wide to dry off after fishing.

Why are there so many at Lake St. Clair Metropark?

Cormorants are colonial nesters, meaning they build their nests close together in large groups rather than spreading out. Islands are a favorite spot because they offer some protection from predators like foxes and raccoons. Dog Island, just off the shore in the Metropark, hosts one of these colonies, with birds building stick nests both in trees and on the ground. Cormorant numbers at the park increase in spring when nesting season begins and decrease in the fall when they migrate south for the winter. Additionally, there may be additional peaks in spring and fall when other cormorants are passing through to or from nesting grounds throughout the Great Lakes region.

What do they eat?

Cormorants almost exclusively eat fish. An adult cormorant eats roughly a pound of fish a day, usually smaller fish under six inches long. What they eat depends a lot on what’s available locally and the time of year, so their diet shifts with the seasons and the body of water.

Do cormorants hurt fish populations?

It’s a fair question, and the honest answer is: it depends. On a large body of water like Lake St. Clair, a few thousand migrating birds passing through for a few days generally has a limited effect. Where cormorants can have a more noticeable, localized impact is around large nesting colonies during breeding season, when adults are feeding close to home for months at a time. This is one of the reasons the Metroparks collaborates with the Michigan Department of Natural Resources on ongoing habitat and wildlife management.

What about the trees on Dog Island?

Cormorant droppings are quite acidic and over time a large colony can stress or kill the trees and vegetation it nests in. That said, Dog Island’s cottonwood trees have also been affected by high water levels and natural aging, so the die-off isn’t attributed to cormorants alone. Some of the trees have begun to fall, signifying that it is inevitable that these trees will come down at some point. This causes issues for navigability around the island.

Is Metroparks planning to Remove Cormorants or Trees from Dog Island?

The Metroparks is committed to ensuring a healthy, balanced ecosystem in our region. We have a long-standing history of working and collaborating with the MDNR on habitat and wildlife management and we are committed to working with them on exploring options for double-crested cormorant population.  If the MDNR determines and recommends that management is the best way forward, we would continue to collaborate on these efforts. Habitat management would not be intended to eliminate cormorants from Dog Island but to limit their expansion and associated impact. MDNR actively manages several breeding colonies annually, all of which continue to support nest cormorants even with active management occurring.

Are cormorants protected?

Yes. Cormorants are a native species that was once common throughout the Great Lakes, but their numbers dropped sharply in the 1900s due to hunting and pesticides like DDT. They’ve been protected under the federal Migratory Bird Treaty Act since 1972, which is why any population management has to go through specific state and federal processes.

Spotting cormorants at the park

Look for them along the shoreline and near Dog Island, especially in the early morning. You’ll often see them perched with wings outstretched or swimming low in the water with just their head and neck visible before they dive. Spring (April through mid-May) and fall (mid-August through September) are the best times to spot them.