Water Intake, Existence Energy, and Responses to Water Deprivation in the Sand Patridge Ammoperdix heyi and the Chukar Alectoris chukar: Two Phasianids of the Negev Desert

Abstract

Two phasianid birds, the sand partridge (Ammoperdix heyi) and the chukar (Alectoris chukar), are sympatric in much of the Negev desert, but the sand partridge also occurs in extremely arid areas where chukars are absent. We compared their water intakes, existence energies, and responses to water deprivation under laboratory conditions. Four chukars (body mass [mb] = 416.1 g) and four sand partridges (mb = 165.0 g) were caged individually in an environment-controlled room (T = 27 C; RH = 42%; 12-h-light:12-h-dark cycle) and were offered high-protein chick starter chow and tap water ad libitum. They were then denied water until they declined to 80% of their initial body mass, and then they were offered water again for 14 days. With ad libitum food and water, no difference between species was found in either relative water intake (per kilogram0.75) or existence energy (per kilogram0.75). During water deprivation, sand partridges lost body mass at a proportionately faster rate than chukars (2.9% vs. 2.0% mb/day; P < .03). Recovery rates of body mass were similar in both species. We found no apparent physiological differences that might explain the ability of sand partridges to inhabit extreme deserts where chukars are absent.