Because evaporative cooling is the principal avenue of heat loss at high am
bient temperatures, high humidity superimposed on high temperature presents
poultry with an additional thermal challenge. Whenever body temperature ex
ceeds ambient temperature, sensible heat loss (radiation, conduction, and c
onvection) to the environment will occur. The generally accepted model of h
eat balance, which states that when ambient temperature increases homeother
ms will endeavour to maximize sensible heat loss before resorting to evapor
ative heat loss, was recently challenged. However, several factors that can
influence heat balance were not considered in the reasoning pursued in tha
t challenge. In this paper the theory behind heat balance models is discuss
ed and the data that were used to challenge the model are reanalysed. The q
uestion of whether poultry are capable of physiologically increasing sensib
le heat loss under hot, humid conditions remains unanswered and presents an
area worthy of future study.