Hi Waveney

How lucky you are to have wild ducks, 3 have moved into the fountains at trafalgar square, but I don't think that they will do nearly so well as the ones on your pond. Dont feed them too much bread it fills them up but doesnt give them the nutrients they need, much like us really! You will probably find that they will compete with the Koi for their pelletts. If you are serious about feeding them you can get of duck food from amazon for Ł5.00

1.5kghttp://www.amazon.co.uk/s/?ie=UTF8&keywords=duck+food&tag=googhydr-21&index=aps&hvadid=689538369&ref=pd_sl_2yga5vlpum_e

and here is some general information about ducks

http://www.callducks.net/feeding_ducklings.htm

of course you know that they are looking for a place to raise their family, so hopefully you will be an aunty to ducklings soon! There is information about feeding ducklings on the site too, oh yes they will make a hell of a mess of your garden!

Good luck with them