In the Wild

• In the wild, swans are foragers, subsisting mainly on the leaves, seeds, stems and tubers of submerged aquatic vegetation, algae, grasses, small invertebrates, larvae, fish and insects. They will also feed on the seeds and young shoots of cultivated grains, such as corn and wheat. Some species eat more meat as babies, switching to a more vegetarian diet as they mature.
  
  

Maintenance Pellet

• Mazuri Waterfowl Maintenance feed or a similar brand can be fed to swans, though they are best combined with fresh greens. According to Mazuri, the main ingredients in its pellets are ground corn, wheat middlings, soybean meal, calcium carbonate and fish meal.
  
  

Fresh Foods

• The Brookfield Zoo in Illinois feeds its trumpeter swans dog chow mixed with fresh greens. Swans may be fed spinach, dark green lettuce, shredded carrots, celery, alfalfa sprouts and other vegetables. Cracked corn, brown rice, lentils and split peas are also acceptable foods.
  
  

Grit

• Some form of grit should be provided for swans. Grit helps the swan break down food in its gizzard before the food travels to its digestive system. Sand or a mixed poultry grit containing limestone, oyster shell and flint are fine for swans.
  
  

Diet-Related Health Issues

• Swans are prone to a condition called "angel wing," wherein the last section of their wings turns upward instead of lying against the body. Angel wing is a severe impediment to flight, often deadly for birds in the wild. Angel wing may be caused by a diet too high in protein and low in vitamins.