My solution is not to feed ad lib. I have measured exactly how much they need per bird, multiply that up by number of birds and divide by three - they get three meals a day in a big flat dish same as me and the dogs, no waste, no mess, no vermin. They get vegetables from time to time, I remove what isn't eaten in a day, they get an extra meal of porridge, honey and milk every couple of days too, same for that - put down, eaten, lift plate.