Body temperatures in free-flying pigeons

We examined the relationship between body temperature (T-b) Of free flying pigeons and ambient water vapor pressure and temperature. Core or near core T-b Of pigeons were measured using thermistors inserted into the cloaca an d connected to small transmitters mounted on the tail feathers of free flyi ng tippler pigeons (Columba livia). Wet and dry bulb temperatures were meas ured using modified transmitters mounted onto free-flying pigeons. These al lowed calculation of relative humidity and hence water vapor pressure at fl ight altitudes. Mean T-b during flight was 42.0 +/- 1.3 degrees C (n = 16). Paired comparisons of a subset of this data indicated that average in-flig ht T-b increased significantly by 1.2 +/- 0.7 degrees C (n = 7) over that o f birds at rest (t = -4.22, P < 0.05, n = 7) within the first 15 min of tak eoff. In addition, there was a small but significant increase in T-b with i ncreasing ambient air (T-a) when individuals on replicate flights (n = 35) were considered. Inclusion of water vapor pressure into the regression mode l did not improve the correlation between body temperature and ambient cond itions. Flight T-b also increased a small (0.5 degrees C) but significant a mount (t = 2.827, P < 0.05, n = 8) from the beginning to the end of a fligh t. The small response of T-b to changing flight conditions presumably refle cts the efficiency of convection as a heat loss mechanism during sustained regular flight. The increase in T-b On landing that occurred in some birds was a probable consequence of a sudden reduction in convective heat loss.