Water Economy of the White-Crowned Sparrow and Its Use of Saline Water

Abstract

The Gambel White-crowned Sparrow (Zonotric~ia Zeucophrys gumbe&) is a conspicuous winter visitant in California, occurring practically everywhere in the state below the snow level and east of the humid coast belt.Included in its winter range are the arid portions of southern California and adjacent regions (Grinnell and Miller, 1944).It is one of the most conspicuous winter-visitant sparrows in Joshua Tree National Monument, located in the transition between the Mojave Desert and the Colorado Desert in California (Miller and Stebbins, 1964).In addition Banks (1963) reports the occurrence of large flocks of White-crowned Sparrows (not subspecifically designated) on several of the desert islands in the Gulf of California during March and April 1962.The physiology of photoperiodically influenced phenomena in the White-crowned Sparrow has been intensively investigated by Farner and his colleagues (for example, Farner, 1964) ; King (1964) has recently reported on its metabolism and body temperature, and Morton (1965) has analyzed its food intake and feeding periodicity.In spite of these many investigations and in spite of its frequent habitation of xeric situations in the winter, information on the water relations of the Whitecrowned Sparrow is fragmentary.This investigation undertakes to examine the water economy of the Whitecrowned Sparrow in order to expand our knowledge of its general biology.Specifically, the study attempts to assess the ability of the White-crowned Sparrow to maintain water balance on the desert and to utilize saline water that may be present in desert springs and as sea water in portions of its winter range. MATERIALS AND METHODSThe 39 Gambel White-crowned Sparrows employed in this investigation were captured between November 1963 and March 1964 near Claremont, Los Angeles County, California.They were confined in an outdoor aviary until needed for experimentation.During experimentation the birds were housed individually in cages measuring 10 X 10 X 10 inches in a windowless room on a 12-hour photoperiod (lights on from 0400 to 1600 hours).Each cage was equipped with an inverted graduated cylinder with an L-shaped drinking tube for measuring fluid intake.Except for studies of water deprivation and utilization of succulent food the birds had unrestricted access to drinking water.The birds were weighed to the nearest 0.1 g on alternate days at the beginning of the dark period.Water intake was measured daily to the nearest 0.5 ml.One drinking device was used as a control to measure evaporation.It was found that the birds could not maintain normal body weight on a carbohydrate-rich diet of mixed bird seed.When provided in excess with chick-starter mash containing 20 per cent protein, the birds remained in excellent condition.The investigation extended from April through July 1964, during which time the room temperature ranged from 20 to 24"C, and relative humidity fluctuated between 30 and 49 per cent.Filtered sea water with a salinity of 33 ppt was obtained from Marineland of the Pacific, Palos Verdes, California.The various