Nutrition in Passerines
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, rape, niger, hemp, linseed, and oats. Most of these commercially available seed mixtures are deficient in numerous vitamins and amino acids. The fat-soluble vitamins A, D3, E, and K are generally low, the calcium:phosphorus ratio is poor, and the amino acids lysine and methionine are insufficient. High amounts of fat in seed-based diets can lead to obesity and to nutritional disorders in the offered food (eg, calcium and vitamin deficiency, as well as an amino acid disorder).
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, which contains balanced nutrients, are offered by many breeders as a nutritionally consistent alternative. Pellets are fed for maintenance or 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 high amounts of fat in seeds.
Soluble grit (ie, oyster shell, cuttlebone) should be provided to canaries and finches. Sprouts, fruits, and vegetables may be psychologically stimulating and enhance breeding in these passerines.
Plumage colors in canaries partially depend on the pigments in the diet. For example, red-colored canaries are fed canthaxanthins before breeding season. Carotenoids vary in their bioavailability, and there are species differences in the types of carotenoids absorbed and metabolized.