The order Passeriformes contains > 5,000 species of birds and includes frugivorous, carnivorous, insectivorous, and granivorous species. Most passerines maintained as pets (finches and canaries) have historically been fed primarily seed and are considered florivorous to granivorous.
Commercial seed mixtures for canaries often contain a mixture of canary, rapeseed, niger, hemp, linseed, and oats. Most commercially available seed mixtures are deficient in numerous vitamins and amino acids. In these seed mixtures, levels of the fat-soluble vitamins A, D3, E, and K are generally low, the calcium:phosphorus ratio is poor, and amounts of the amino acids lysine and methionine are insufficient. High amounts of fat in seed-based diets can lead to obesity and to nutritional disorders (eg, calcium and vitamin deficiency, as well as disorders associated with low levels of specific amino acids).
Egg food (hard-boiled egg–based soft food with added vitamins and minerals) has traditionally been fed by canary breeders during the reproductive season, with soaked seed added to increase acceptance. Extruded pellets, such as organic pellets or pellet-based mash containing balanced nutrients, are offered by many breeders and recommended by many veterinarians as a nutritionally consistent alternative. Pellets are fed for both maintenance and breeding purposes. Extruded pellets fed for breeding contain 18–22% crude protein as well as a limited amount of fat (5–8%) compared with the higher amounts of fat in seeds.
Soluble grit (ie, oyster shell, cuttlebone) should be provided to canaries and finches as a calcium supplement, particularly during egg-laying periods. Sprouts, fruits, and vegetables also may be offered to both psychologically stimulate passerines and enhance their breeding by simulating their natural behaviors of eating and interacting.
Plumage colors in canaries partially depend on pigments in the diet. For example, red-colored canaries are fed the naturally occurring orange-red carotenoid canthaxanthin before breeding season. Carotenoids vary in their bioavailability, and there are species differences in the types of carotenoids absorbed and metabolized.
