The volume and force of their seemingly effortless song gives the impression of happiness, but also creates a mystery of how a body weighing less than one ounce and a voice box no larger than a small green pea can produce such intense sounds. Nature seems to tell canaries not to announce their presence if their health is less than perfect. Survival in the wild often depends on the predator NOT knowing the location of the bird. In addition, the absence of song in the male canary stops courtship and mating, insuring only the fittest birds reproduce. When male canaries don't sing they are either molting or have a health problem.
Canaries normally sing year-round except during the molting period and a short time thereafter.
Song stops because of the physical and nutritional stress from growing up to 2,000 new feathers. Canaries actually announce problems to their owners by being quiet. When this happens, see your veterinarian. In captivity, the most common abnormality to affect singing in male canaries is nutritional deficiencies. As with any other animal, canaries require balanced diets, but the seed diets traditionally offered to canaries are lacking in vitamins, minerals and proteins.