TEMPERATURE REGULATION OF THE GREAT GREY SHRIKE (LANIUS EXCUBITOR) INTHE NEGEV DESERT .1. LABORATORY MEASUREMENTS OF METABOLIC-RATE AND EVAPORATIVE WATER-LOSS

1. Great grey shrikes (Lanius excubitor, body mass = 55-65 g) are foun d over much of the Holarctic, including the most severe deserts in the Middle East. We examined their thermoregulatory characteristics to de termine how they manage heat balance in a wide range of thermal condit ions, particularly those experienced in the hot Negev desert of Israel . 2. Great grey shrikes showed physiological characteristics similar t o those found in most other passerine species of similar size, with tw o notable exceptions. (a) The rate of increase of evaporative water lo ss with increasing ambient temperature above their upper critical temp erature 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 incr easing ambient temperature within the thermoneutral zone; this control led hyperthermia leads to a saving of water.