I do agree that there are ways to deal with any environmental extreme -- people raise chickens, a bird whose natural environment is tropical, in sub-Arctic Alaska. But the only breed that I've had that had difficulty with the heat was my Cuckoo Marans. I lost three hens to heat, two one year and one the next year. They had shade and water, and none of my other birds seemed to have any problems. Maybe it was just that strain of Marans, I don't know. But I'd certainly take special precautions for them if I had them again, while I don't need to do anything special for my other birds.
Kathleen