Cutaneous Water Loss in the Roadrunner and Poor-Will

Avian physiologists have generally assumed that since birds lack sweat glands, cutaneous evaporation is negligible. However, recent data indicate that the skin represents a major avenue of evaporative water loss (EWL) in the Painted Quail (ExcaZfactoria chine&z), Village Weaver (Ploceus cucullatus), Budgerigar ( Melopsittacus undulatus), Zebra Finch (Poephi&z ca.stunotis) (Bernstein 1969, 1970, 1971a, b), and the Domestic Pigeon (Columba Z&a) (Smith 1969; Smith and Suthers 1969). Not all birds lose large amounts of water through the skin. SchmidtNielsen et al. ( 19’ 69) state that the skin plays a minor role in EWL in Ostriches (Struthio cameZus), contributing less than 2 percent of total evaporation at 40°C. The purpose of this study was to examine cutaneous evaporation in two North American desert-inhabiting birds, the Roadrunner (Geococcyx californianus) and the Poor-will ( PhaZaenoptiZus nuttalk). Oxygen consumption and EWL have been studied previously in both species over a wide range of ambient temperatures (Bartholomew et al. 1957; Bartholomew et al. 1962; Calder and Schmidt-Nielsen 1967; Lasiewski 1969; Lowe and Hinds 1969).