The average domestic canary weighs between 0.4 and 1 ounce. There is no difference in size between male and female birds, but the sexes are easily distinguished by the song and bright coloration of the males.
Domestic canaries are descendants of the island canary, a bird native to coastal North African islands. They are similar in size to the European canary, but they are heavier and less squat than these birds. In the wild, the average weight of island canaries is half an ounce, not much different from their domesticated cousins. The small size of canaries lends them a rapid metabolism which makes them more susceptible to environmental contaminants, hence their use in coal mines as living carbon monoxide detectors.