Canadian geese and domesticated geese are both primarily herbivores. According to The Cornell Lab of Ornithology, their diets consist of grass, aquatic plants, grains and leaves. Although Canadian geese occasionally eat small fish, domesticated geese are not reported to do so.
Most goose species are herbivorous, with the notable exception of the Egyptian goose, a species not closely related to the common domesticated goose. Like the Canadian and domestic goose, it eats a great deal of plant matter but also seeks out insects, snails, crabs and small fish. While it is an exception to the rule, this omnivorous goose species does not relying primarily on a diet of fish as certain birds of prey do.