Why do birds need so much food?
Birds need to consume lots and lots of food so it will have enough energy to fly. If it didn't consume enough food it would be too tired to fly
Birds like dog food so you would need to move the dog food to a location where the birds can't get to it. But why would you care if they ate the dog's food. We actually have a pet starling (they talk and imitate incredibly!) and we feed him dog food as recommended by other starling owners and vets, since the dog food is so well balanced in nutrients.