When in Broomfield Park I often see people feeding bread to the water fowl, ignoring the signs asking them not to. On one occasion I pointed out the signs to someone who was in the process of throwing bread in one of the lakes, only to be told "No, that's wrong."
Well, it turns out that the notices are right. There are a number of reasons why you shouldn't throw bread in the water. Not only is it bad for the ducks, but it can cause various other problems, such as encouraging growth of algae and spreading disease. However, according to the Canal & River Trust, nearly three-quarters of the population throw leftover bread into canals, rivers, reservoirs and lakes.
The reasons for not feeding ducks bread, and a list of things you should feed them, can be found on the Trust's website.
Recommended foods are sweetcorn, lettuce, frozen peas (defrosted!), oats, seeds and rice.
As well as not throwing bread in ponds, you shouldn't feed ducks crisps or other junk food, popcorn, cornflakes, oranges and other citrus fruit, onions, spinach or avocados.
See the links below for more detailed information.