Water Economy and Salt Balance in White-Winged and Inca Doves

Abstract

Two of the most conspicuously abundant birds during the summer in the Sonoran desert regions of southern Arizona and northern Mexico are White-winged Doves (Zenaida asiatica) and Inca Doves (Scardafella inca). These doves have nearly identical general distributions extending over arid parts of the southwestern United States and south through Mexico into Central America. However, within this range Inca Doves are confined to desert towns and villages while White-winged Doves occur throughout the deserts (Ridgway, 1916; Bent, 1932). In addition there are seasonal differences in distribution at least within the United States, with the strong-flying White-winged Doves represented only as spring and summer residents while the relatively sedentary Inca Doves are continuously resident (Bent, 1932). In their enlightening review article on the water economy of land birds, Bartholomew and Cade (1963) indicate an apparent direct relationship between body weight and efficiency of osmotic homeostasis. The differences in body weight between White-winged Doves (ca. 140 g) and Inca Doves (ca. 40 g), together with differences in habitat preference and mobility in the same desert macroenvironment, afforded an excellent opportunity to test the proposed relationship between body weight and water economy in two closely related land birds. Therefore, this study undertakes to examine the water relations of White-winged and Inca doves in light of taxonomic affinity, similarity of macroenvironment, and differences in body size, mobility, and microenvironmental preferences.