There is an article on doing surgery on an impacted crop in this month's Backyard Poultry magazine. Since this is a common thing to happen and with most of us not having aviary vets available to us it is a must read. It does not go into enough detail to save your chicken but jeaucamom has an excellent post to back up the article here. Not for the feint at heart but this is necessary information if we are to raise chickens.