Responses to Intermittent Water Intakes in Sand Partridges and Chukars

Abstract

The abilities to maintain body mass (mb) during water deprivation and to recover mb when water becomes available were compared in captive sand partridges (Ammoperdix heyi) and chukars (Alectoris chukar sinaica). These two phasianids are broadly sympatric in the Negev Desert; however, sand partridges, the smaller and paler of the two, inhabit extremely arid areas where chukars are absent. Six sand partridges and five chukars were offered water following 1, 2, 3, 4, 5, and 6 days of water deprivation. There were five successive trials in each water treatment except the first, when there were 10 trials. Rates of mb loss at 1-3 days of water deprivation were higher in chukars (1.5%-2.8% mb/day) than in sand partridges (1.3%-2.2%), but were similar at 4-6 days of water deprivation (1.2%-1.3% mb per day). Sand partridges consistently recovered mb better than chukars, and the difference was significant in the 5-day treatment. When the birds received water every 6 days, plasma osmolality was 346 mOsm/kg in sand partridges and 356 mOsm/kg in chukars immediately after drinking and increased to 374 mOsm/kg and 376 mOsm/kg, respectively, with water deprivation. Following drinking, the water in excreta was 93% in chukars and 77% in sand partridges (P < .01) and fell to 57% and 59%, respectively, with water deprivation. Evaporative water loss (EWL) during 6 days of water deprivation was 41% of the total water loss for sand partridges, or 1.3% mb per day, and 60% of the total water loss for chukars, or 1.8% mb per day. These rates declined to 1.1% and 1.5% mb per day for sand partridges and chukars, respectively, during the last 3 days of the 6 days of water deprivation. Sand partridges apparently are better able to maintain mb during water deprivation and are better able to recover mb with intermittent drinking. These advantages of the sand partridges are mainly due to their lower EWL when compared with the chukars and may explain in part how they can inhabit extremely arid areas where chukars are absent.