The best I've heard ( but haven't tried) is to use clay tile, like the terra cotta flower pots, but tiles not pots. Soak them overnight and set them on the ground in the morning. The birds can stand/lay on them and the evaporation cools them. Anything I do will not last the entire time I'm at work. They are in a pen 1/2 acre (5 birds) with shade but I let them out into the entire yard when it's like today--106 and so thick you could cut the air with a knife. They usually go to the shady spot under the camper, which is under a shed roof, so they get a breeze and nice shady spot. I leave water all over for them, but they like the ac condensation best.....I usually leave a dog bowl there to catch it since that's where they go. Dust baths and shade is the answer. Mine will pant (when they run over for a cracker) but I rarely see wings held out for cooling.