I am having the same problem.Its driving me nuts.Not only do they eat my chickens feed.They poop in the feeder.and I have a heated water bowl to keep the water from freezing.they poop in that.they also have started roosting in the roofed runs.i spend so much time trying to keep it clean.
This is tough....Ideally we want our egg laying chickens to "free range" and be happy...Recently I decided to throw sparrow seed around the chicken coup..thinking this may keep them from actually going inside the coop and taking my silkies food. I'll let you know how that works out...
I'm having the same problem. i moved the feed back inside coop and i find almost a doz sparrows feeding in the coop. right now we have a human sized door. I'm thinking that when i install the auto chicken door the problem will lessen. i will hang shiny streamers, perhaps, as a deterrent. hoping that won't keep the chickens from entering the coop.
We have sparrows too and we had a lot of mice. On YouTube I watched a video of a chicken feeder made from a five gallon bucket. You hang it up. There is a hole in the bottom with a large bolt that hangs out of the hole. The chickens learn to look up and peck at the bolt and food falls for them to eat but mice and birds can't get to it. We still have some sparrows but no more mice.also it is protected from rain. Its helpful