Going to a pond and throwing bits of bread to the flocks of ducks and geese is an enjoyable pastime for many people, but it might not be such a good idea for the birds themselves.
Bread has very little nutritional value for wild birds as it contains little to no protein and too much salt. Filling birds up with bread will discourage them from looking for other healthier foods and could lead to stunted growth, malnutrition and other problems.
Birds that are regularly offered bread can become dependent on the easy and unhealthy food source, putting them at risk for starvation if the supply of bread suddenly stops.
Feeding bread to birds in the spring can be especially dangerous as chicks are at risk for not getting enough essential nutrients for healthy growth and could die or grow to be weak adults.
Birds, especially seagulls, that are regularly fed bread by humans can become bold and less afraid--coming up to people while they are eating lunch at the park or even nipping at children as they eat a sandwich. Throwing bread crumbs into the center of a flock can also trigger aggression and fighting amongst the birds themselves.
Those who really love feeding the birds but want to do it responsibly can try other more nutritional substitutes like grated cheese, breakfast cereals, crumbled biscuits and porridge oats.