Are they lead or are they slightly magnetic? If lead, that is bad for all birds and shouldn't ever be used. If they are magnetic, you could put a magnet on a stick and pick them up buy sweeping the area with the magnet.
Otherwise, I don't know, other than start being more careful about where you shoot and try to pick up what you can.
I have a few around my yard and have not noticed my flock eating them. I know they try everything at least once but have not seen them try to eat any yet.
I'll guess I'll just try and make sure that where we do airsoft is far away from where the chickens would be free ranging. Anyone else have suggestions/experience regarding this problem?
My birds would pick the AS BB's up in thier beak and run arround with them when they were young. After awhile they would drop them. Most times they would drop them near thier coop. I just pick them up and throw them away. I've never seen a chicken eat one. I was more like they wanted someone to chase them. I think they know the BB's are not food and just are having a bit of fun.