Swans natural food is water plants. An adult swan would eat about 4kg a day. If there are few water plants, as in many big rivers and canals, they are glad of extra help.
Natural food you can give. Delight them with dandelion leaves, short unsprayed grass cuttings, water cress, lettuce leaves (soft green round lettuce is best), oats, spinach, shredded sweetheart cabbage, defrosted sweetcorn or peas (shallow water only).
Mixed corn (wheat + dried corn) is one of the least expensive foods. You can buy a 20kg sack for about £9.50 in country stores. You need to place the corn in shallow water or it will sink out of reach of the swans – they can only reach down about 90cm. In Worcester, this means using the first underwater step of the Birmingham University boathouse steps in the swan sanctuary. Canals are too deep unless you can find an underwater ledge.
Floating swan & duck pellets are a great option as they are specifically formulated for feeding swans. They’re good value too, as the swans can eat the floating pellets before they sink, and the pellets will keep if the swans are not hungry when you visit. The Swan Food Project runs a Community Purchase Scheme to provide discounted sacks of pellets to the public, and has outlets throughout Worcester selling handy bags of pellets. If these sources are not convenient, try your local pet shop or online supplier.
For young cygnets put some floating duck and swan pellets in a jar with water before setting off. By the time you arrive they will have gone soft enough for the cygnets to be able to nibble them.