Temperature regulation of the great grey shrike (Lanius excubitor) in the Negev desert-I. Laboratory measurements of metabolic rate and evaporative water loss

1. 1. Great grey shrikes (Lanius excubitor, body mass = 55-65 g) are found over much of the Holarctic, including the most severe deserts in the Middle East. We examined their thermoregulatory characteristics to determine how they manage heat balance in a wide range of thermal conditions, particularly those experienced in the hot Negev desert of Israel. 2. 2. Great grey shrikes showed physiological characteristics similar to those found in most other passerine species of similar size, with two notable exceptions. (a) The rate of increase of evaporative water loss with increasing ambient temperature above their upper critical temperature was 40% higher than allometrically predicted for a bird of the same body mass and similar to that recorded for other desert-dwelling birds. (b) Body temperature in great grey shrikes increased with increasing ambient temperature within the thermoneutral zone; this controlled hyperthermia leads to a saving of water.