Effects of lead on avian thermoregulation in the heat: An experimental test with pied crows (Corvus albus)

Many of the negative physiological effects of lead involve the hypothalamus, but the possibility that thermoregulation is affected has received little attention. We tested the hypothesis that lead exposure reduces avian thermoregulatory performance under hot conditions in pied crows (Corvus albus) experimentally exposed to lead in their diet. Crows in our high lead treatment (blood [Pb] = 87.3 ± 44.7 μg dL^-1) showed significantly higher air temperature (T_air) inflections for evaporative water loss (EWL) and resting metabolic rate (RMR) compared to control (6.4 ± 1.8 μg dL^-1) or intermediate (53.9 ± 23.7 μg dL^-1) lead groups, which did not differ. EWL, RMR and body temperature (T_b) all increased more rapidly at T_air > T_b in the high lead treatment. In contrast, neither maximum T_air tolerated by the crows nor maximum T_b varied with treatment. Our data reveal that water and energy balance during hot weather is affected by lead exposure.