Figure 2.

Male cloacal temperature. Mean ± s.e. of cloacal temperature on given experimental day over two experimental heat exposure periods (separated by vertical hatched line). Spacing between time points is related to sampling on experimental day, not continuous time. Day 1 reflects measurements taken under baseline conditions immediately prior to heat exposure. Males exposed first to 40°C in part 1 of experiment then to 30°C in part 2 (solid line), or 30°C then 40°C (dashed line). Experimental heat exposure: 30°C (circles) or 40°C (triangles). During experimental treatment birds were exposed to heat for 8 h a day and returned to 23°C for 16 h (white background). During acclimation and recovery periods birds were kept continuously at 23°C (shaded background).