All my birds seem to handle the heat ok. It does not get super hot or cold here. We get some days with a heat index about 100, but not many. I build my coops for summer and then take some steps to winterize them. I have literally hundreds of birds, so some level of mortality is to be expected. Any breeds that have abnormally high mortalities get sold out and I stop keeping them.Do they seem to handle heat well? I would assume not because of all those heavy feathers, but I've also seem some very fluffy birds do quite well.