Nutrition-You are what you eat!

           As mentioned in the habitat section, black-necked swans live in regions adjacent to water, feeding on aquatic plants, insects, and some fish spawn.  This diet classifies them as omnivores, feeding on both heterotrophic and autotrophic organisms.  Swans most commonly feed on aquatic plants such as Brazilian waterweed, stonewort, and pondweed.  Besides having legs specialized for swimming, they also have jagged edged bills that allow them to filter food from the water.  Their rough tongue is another adaptation that allows them to grasp slippery plant matter.  Swans, like other chordates, have a complete digestive tract that includes a mouth, esophagus, stomach, small intestine, large intestine, rectum, and anus.  The digestive tract also includes organs such as the pancreas and liver, which aid in digestion though secretions such as bile.  As is typical in most omnivores, the intestines are elongated to aid in absorption of as many nutrients as possible. As a group, swans have a low ability to digest and absorb nutrients from the plant matter they eat.  Due to high levels of cellulose and fiber, swans are able to digest only 21-34% of the plant matter they ingest .  This characteristic limits them, forcing swans to devote much of their time to eating in order to receive proper nutrition.

            Swans have a closed circulatory system, meaning blood is contained within vessels and there is separation between the blood and interstitial fluid.  Their four chambered heart pumps oxygenated blood out to the tissues, while deoxygenated blood returns to the heart to be exchanged by the lungs.

 Stonewart, a common meal for this swan. Brazilian waterweed, another tasty dish!