Ducks, Gulls, and Predators
— Natural History —
Food and Shelter
The mouth of the river and harbor provide waterfowl and waterbirds an environment sheltered from the winter gales of Lake Ontario. The breakwalls serve as resting places for the gulls where any approaching predator may be quickly detected, while at the river's mouth, shielded from the storm waves, diving ducks harvest food.
The large flocks present provide enhanced opportunities for social interactions among individuals to aid them in finding mates for the summer. For these birds it is a winter vacation spot, a safe place to prepare for the next breeding season.
By mid-January courtship begins in many ducks. Warm sunny days trigger courtship rituals among male ducks. Several male Common Goldeneye may display for a single female, each one trying to impress her more than his rivals. With heads pumping back and forth.
The large flocks of gulls and waterfowl found here attract predators, including Bald Eagle and Snowy Owl. An adult Bald Eagle will flush a flock of ducks, then hover over any sick or injured bird. The weak bird will dive repeatedly until exhausted, when it is plucked from the water by the waiting eagle. The predators provide a service to the prey species by removing sick birds and limiting the spread of disease, while these magnificent birds of prey are sustained through the winter to migrate and breed again.
There are four species of common gulls here; Great Black-backed, Herring, Ring-billed and Bonaparte's. As the Bonaparte's depart in early winter, rare Arctic gulls including Glaucous and Iceland Gull arrive. These birds have pure white immature plumages and adults lack black wing tips. Gulls often steal food from diving ducks. Large species, such as Glaucous and Great Black-backed, may take small waterfowl and gulls.
Diving ducks such as Common Goldeneye, Bufflehead, greater Scaup and Long-tailed Duck predominate amongst wintering waterfowl flocks. Dabblers including Mallard, American Black Duck and Gadwall occur, but the fast running river water and the deep harbor are better diving duck habitat. Ducks that can dive to depths of 20 or more meters find that food is readily available.