Comparative studies of thermoregulatory and osmoregulatory behaviour and physiology of five species of sandgrouse (Aves: Pterocliidae) in Morocco



In Morocco, Pterocles alchata and orientalis prefer steppe habitats, while coronatus, senegallus and lichtensteini prefer deserts, so that these species groups are largely allopatric under normal climatic conditions. Both habitats impose extreme thermal conditions (air temperatures up to 55°C) on these diurnally active birds which characteristically nest in the open. Sandgrouse minimize environmental and metabolic heat loads by concentrating vigorous activity into the cooler parts of the day, by remaining inactive when the sun is high, and (exceptionally among the bird species studied) by increasing thermal insulation when ambient temperatures exceed body temperatures. Water conservation is achieved by delaying evaporative heat dispersal mechanisms (gular fluttering and gaping, but not panting) until air temperatures reach 50°C, and probably also by a renal-colonic system adapted to oliguria and salt retention. Desert and steppe study sites had permanent and comparatively fresh water supplies, but appeared to be salt deficient. Morning drinking flights in alchata and orientalis showed evidence of a “feed forward” response enabling increasing numbers of birds to drink earlier in the day in anticipation of hotter conditions later. P. coronatus, senegallus and lichtensteini breast feathers are adapted for water transport (we have no data for alchata and orientalis), and show specializations in keratin-water interactions (not seen in Melopsittacus undulatus or C. coturnix) enabling more rapid feather water uptake.