He can have sunflower seeds or millet in moderation, but large amounts can cause trouble. It is also like scratch and not very nutritious, more like a treat. It's hard to change a duck from what it is used to, so it won't be easy to get him eating greens etc. try sprouting some wheat or barley, dried peas or lentils for now. It looks more like seed to him and is much more nutritious. It only takes around 2 days to sprout them. Tom did eat some Mazuri Waterfowl pellets at the meetup (when my daughter fed him and the others all Leah's food ). You can get that at JC Feed or Carter's Hay & Grain in Lakeside, they only sell large 50# bags though. You could also feed him gamebird or turkey feed, it's pretty much same as chicken feed but higher protein. Any chicken food (besides scratch or any medicated) would be better for him than what people give. You can buy it by the lb instead of large bags at East County Feed in Santee. It's probably best to not feed him though, if he is 15+ years old, then he has survived off more than people feeding him. He must have a decent food source, if people don't feed him he probably just goes out and finds a way to feed himself. He must be for him to have lived that long. If he is really that old, he likely isn't going to be around too much longer, ducks generally live 10-15 years when fed proper diet in captivity. The people giving bread would be the cause for liver problems, it causes fatty deposits to develope around the liver, had he been totally dependant on them as a main source of food, he would have died many years ago. The ducks and birds are actually better off in the winter when they aren't being fed as much because they are forced to migrate to other areas and find/forage/hunt the proper food for themselves. Don't worry about them starving, being hungry forces them to fend for themselves, find another food source and learn not to be completely dependant. I hope I didn't seem rude or anything. I know you care about them and want the best for them. I care too. I love ducks (and all animals) and feel sorry for what they go through in the public lakes and parks. I'd bring them all home if I could!