Salt and Water Balance in Seaside and Sharp-Tailed Sparrows

Abstract

THE aim of this study was to obtain data on drinking habits, capacities for concentrating urine, weight maintenance, and blood plasma regulation in the Sharp-tailed Sparrow (Ammospiza caudacuta) and the Seaside Sparrow (A. maritima) taken from different habitats and in different seasons. I studied A. maritima, a salt-marsh species, A. c. caudacuta, which also breeds in salt marshes, and A. c. subvirgata, which breeds in brackish and freshwater habitats. I have compared these species with both freshand saltwater races of Song Sparrows (Melospiza melodia) and Savannah Sparrows (Passerculus sandwichensis). In these latter two species, differences have been demonstrated between saltand freshwater forms in drinking habits and physiological capacities (Cade and Bartholomew, 1959; Poulson and Bartholomew, 1962; Bartholomew and Cade, 1963). Seasonal differences in the environment exist in the area where the experimental birds were obtained. The birds must make more use of seeds and brackish water in their diet in the fall than in the spring; in the fall terrestrial arthropods are scarce and less fresh water is available from dew, coastal fog, and rain. Therefore, I compared the responses of fall-captured birds with those of birds caught in the spring.