Penguins, pelicans, and other fish-eating species in the wild feed primarily on fish, crustaceans, and squid. These food sources vary widely in their fatty acid, vitamin, and carbohydrate contents. In captivity, squid, smelt, herring, mackerel, and whiting fish are commonly available. One of the most important aspects of feeding piscivorous birds is fish quality (see Nutrition in Marine Mammals). All diets of fish-eating birds should contain several fish species. Captive seabirds develop strong preferences for a particular fish if it is fed exclusively for prolonged periods, which leads to both nutritional deficiencies and inanition if the feeder fish becomes unavailable.
Supplements commonly given to captive penguins include salt, fatty acids, and vitamins A, D, and E. The need for these and the quantity that must be supplemented depends on the quality and content of the primary diet. Dietary salt (NaCl; 0.5–1 g salt/bird/day) is often provided to birds in freshwater exhibits to help maintain proper functioning of the salt glands.
Providing a supplemental source of essential fatty acids has been recommended during reproduction and molting when smelt is the primary diet.
The process of thawing fish in running water depletes them of water-soluble vitamins. Additionally, many fish contain thiaminase, leading to thiamine (B1) deficiency.
Supplementation of thiamine is recommended at 25–30 mg/kg fish, daily or at least twice weekly.
Most fish are deficient in vitamin E. Clinical signs of vitamin E deficiency include weakness and inability to stand or hold wings in normal posture. Severe generalized myopathy with muscle atrophy, degeneration and necrosis, and replacement with fibrous connective tissue can occur with chronic pronounced vitamin E deficiency. Supplementation with 25–100 IU vitamin E/kg fish has been proposed. However, oversupplementation (500–10,500 IU vitamin E/kg food) may result in decreased growth and coagulation disorders, possibly from creating vitamin K deficiency rather than directly from vitamin E toxicity.
Hand feeding of species and individuals of concern will ensure that each bird receives the proper amount of food and supplement. Some piscivorous species will accept commercial bird-of-prey diets, trout pellets, and/or mice in the diet, as well as fish.
Last full review/revision July 2011 by Joeke Nijboer, PhD; Teresa L. Lightfoot, DVM, DABVP (Avian)