Swans are grazing birds and will eat aquatic vegetation, grasses, petunias, coleus, and other salad type plants. Swans are clean birds when it comes to their habitat and if in their eyes the area needs weeding, pruning or generally tidied they will help. Swans can get into areas such as pampas and other reeds and strip them for nesting materials. If the swan likes that particular area (your garden) because it wants to have the cygnets sun themselves or spend the night and it is free from predators, the swan may strip the plants to lower the stalks and make a small bedding area for the family. The Regal Swan