Ontario’s provincial bird is the beautiful and majestic Common Loon. At about 60 cm long (2 ft.), it is a large compared to other loon species. Its head and neck are black with a greenish gloss. Its bill is black. An incomplete collar adorns its neck in the form of a white bar across the front of the throat. Its back is distinctly chequered with black and white, and its belly is white. Males and females look alike, although the male is, on average, larger.

The name "loon" is derived from a Scandinavian word that means "clumsy". A loon’s legs are placed very far back on its body, which makes the bird very agile in water but ungainly on land. Loons are excellent swimmers and divers, able to overtake fish using mostly just their feet, although they will use their wings from time to time. Ordinarily, loons do not stay underwater for more than minute, but if alarmed by something above the surface, they can stay under for more than three minutes. They can ride low in the water and even lower themselves down and out of sight by compressing their feathers and forcing the air out of their lungs.

In early spring, as soon as the ice thaws, males and females arrive at the breeding territory. A breeding pair will establish an area of about 24 to 80 hectares (60 to 200 acres), which they patrol regularly. Both sexes defend the territory using physical displays, and males also do so using vocalizations such as a loud, yodelling cries. Usually there is only one breeding pair of loons per lake, but if the lake is large enough, two or more may be present.

Loons begin to breed around the age of two or three. Eggs are laid at the beginning of June, and the chicks usually hatch before the end of the month. Males and females build the nest together, using soil, moss and other vegetation. The nest is usually in a sheltered area near deep water, which allows the parents to come and go undetected by predators. If threatened, loons might attack: they rush at the attacker, attempting to impale it with their bills.

The Common loon is a regular sighting throughout most of Canada. During the non-breeding season it migrates to warmer areas around the Gulf of Mexico and on the east and west coasts of North America. The Common Loon breeds in most areas of Canada from Yukon Territory and British Columbia to the island of Newfoundland, as well as through the northern part of the United States.