4 signs of environmental stress
If a coop is too hot, birds may cluster along the walls. Chicks will be on walls of a brooder, as far from the heat source as possible.
They will sit with beaks open, necks stretched out, wings hanging loose beside their bodies, and there will be no noise.
Beaks and wattles may appear dark red and they will die lying with legs stretched out behind and necks stretched forward.
Very cold chicks will huddle together, often standing quite upright with eyes closed and making very plaintive (sad) cheeping sounds.