There have been a few reported cases where swans are becoming ill apparently due to people feeding them white bread. This may be due to the lack of nutrients found in white bread. The illness usually leaves them weak and so unable to forage for their own food. The cases are just reports and it may be that other factors such as overcrowding were involved in causing the swans to become ill. Generally white bread probably doesn’t do swans long term damage but you should still avoid using it as there are healthier alternatives.
Swans naturally feed on pond weed and other aquatic plants and invertebrates and will survive without the additional feeding from humans. However, if you still wish to feed swans, brown bread, seeds and vegetables are much healthier for them. Also remember to feed them in water to discourage them from coming onto the bank and to enable them to swallow water along with the food. If using bread make sure it isn’t stale as mould is poisonous to swans.
Picture by Linda Bunton