There a so many good suggestions on several threads. Search fire ants and look at previous discussions. I have not dealt yet with regular or fire ants in my chicken areas, but if I do, there are a lot of suggestions there by folks who have dealt with the ants.
Sevin dust (5%) works on fire ants where I live. Don't let your chickens breathe it in and make sure it doesn't get in their food or water. It's supposed to be relatively safe to use around chickens, although I think that's debatable. The consequences of a fire ant infestation, in my opinion, outweigh the possible health complications. I just use it in moderation.
EDIT: We now use it on all fire ant mounds in the yard because it's been more effective than actual fire ant killer products.
Jinxed myself by mentioning had never had fire ants in my chicken area. This am my DH found a mound that sprung overnite, it's just outside their run so we were able to use regular fire ant bait.
Don't remember which tread recently or who contributed the idea, but they made a wood framed wire cover, treated the ant mound, covered it with the frame so chickens couldn't get to the ?seven or ? bait until it was gone and would not then be harmful to the chickens.