The Water and Electrolyte Metabolism of Free-Ranging and Captive White-Browed Scrubwrens, Sericornis-Frontalis (Acanthizidae), From Arid, Semi-Arid and Mesic Environments

Abstract

Seasonal variations in water and sodium turnover of resident populations of free-ranging Sericornis frontalis were measured at three sites in Western Australia ranging from arid, through semi-arid to mesic environments. Scrubwrens at all three sites maintained water and sodium balance despite the wide variation in environment. During winter at semi-arid Eyre, however, scrubwrens had a greatly increased dietary sodium intake resulting from the deposition of airborne oceanic salt over the coastal dunes. Scrubwrens at arid Hamelin had significantly lower water turnover rates (e.g. 1.3 ml 10 g-'d-') than those at Eyre and mesic Rockingham during hot, dry periods. The highest rates of water turnover were recorded at Rockingham during wet winters. We discuss the ecological implications of these results. In laboratory studies, scrubwrens from arid regions consumed NaCl solutions of up to 0.8 mol l-', compared with a maximum of only 0.6 ml l-' by scrubwrens from semi-arid and mesic regions. Shark Bay scrubwrens also had a much greater renal-concentrating ability which may be partially accounted for by the larger proportion of medullary tissue in the kidneys of these birds.