Common Loons are not ducks, they are a considered a water bird of their own classification. They are large birds that live on wooded lakes while breeding, they have distinct black above and white below bodies with a checkerboard back, white striped neck, red eyes, and pointy black bill. They are brownish during non-breeding season. Loons feed on fish, crustaceans, insect larvae, and mollusks. Here are a couple I saw while on a lake in northern Wisconsin.