not an expert, but to me heat tolerant means they shouldn't drop dead of heat stroke in the middle of the summer. i think most chickens pretty much slow down in the laying when it hits 100+ here. i got 6 eggs yesterday from 14 hens that should be laying. granted, 3 are broody, some are dar's ameraucanas and if i remember correctly they seem to just shut down in the summer. i guess it will be brown eggs this summer, but i'll take what i can get.
the mediterranean breeds are supposed to fair better here than other breeds. i am slowly working out those that are less heat and disease resistant resistant and keeping those that are: sex-links, welsummers, basque. some breeds i just can't possibly do away with though like my silkies, dark brahmas and dar's ameraucanas.
fyi, the 5 week old muscovy quads are chasing flies this morning
ya hear that memphis?????????????????????