You can flood the coop area to chase them out. I then treat my entire yard (except the coop area, or anyplace the chickens eat or roll in the dirt. ) with a professional fire ant killer Talstar thats non systemic. (It won't go up into the grass my free range birds graze on). You can get Talstar at a chain called "U killem pest control". I also run a border around the coop of the killer. It needs to be applied per directions and watered in good several times before I let my girls back into that part of the yard, I wait a few 2-3 weeks even. I go to the extent of running a temp. fence to section off my yard to keep them out and still let them free range during the day. I also don't feed them people food in the coop anylonger. The feed doesn't seem to attract them as much as food. It's a battle, Talstar lasts about 9 months before re-treatment is needed here in Florida. I'm interisted in what other folks do to deter them also. Ohh, in the coop, I use hay for bedding, and I put de under the bedding also indoors.