Temperature regulation of the great grey shrike (Lanius excubitor) in the Negev desert-II. Field measurements of standard operative temperatures and behaviour

1. 1. Great grey shrikes (Lanius excubitor) are found over much of the Holarctic, including the most severe deserts in the Middle East. We measured operative environmental temperatures of great grey shrikes using unheated taxidermic mounts in the field in summer and winter, and calculated standard operative temperatures from these values. 2. 2. Resistance to heat loss in the shrikes was low compared to other small endotherms. 3. 3. Standard operative temperature lies within the thermoneutral zone throughout the shrikes' morning and afternoon foraging periods in summer. In winter, standard operative temperature was below lower critical temperature throughout the day. 4. 4. We found no significant relationship between activity of these shrikes and standard operative temperature in winter.