| 1. |
Brain (hypothalamic) and cloacal temperatures were measured in heat-stressed Lesser Nighthawks (Chordeiles acutipennis), Mallards (Anas platyrhynchos), Pigeons (Columba livia), and White-Necked Ravens (Corvus cryptoleucus) and in one Roadrunner (Geococcyx californianus). Range of mean body masses was 0.047 to 1.156 kg.
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| 2. |
In all these species brain temperatures were always below cloacal temperatures (Fig. 1). The body-to-brain temperature difference was maintained nearly constant within a species over a wide range of cloacal and air temperatures, and varied in magnitude from 0.80°C in the Roadrunner to 1.29°C in Mallards.
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| 3. |
The presence of arete mirabile ophthalmicum was demonstrated in all five species. This rete may be associated with the observed pattern of brain temperature control.
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| 4. |
The body-to-brain temperature difference may be important in avoiding brain damage during core hyperthermia.
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