Cutaneous Water Loss in the Roadrunner and Poor-Will

Abstract

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 (Excalfactoria chinensis), Village Weaver (Ploceus cucullatus), Budgerigar (Melopsittacus undulatus), Zebra Finch (Poephila castanotis) (Bernstein 1969, 1970, 1971a, b), and the Domestic Pigeon (Columba livia) (Smith 1969; Smith and Suthers 1969). Not all birds lose large amounts of water through the skin. SchmidtNielsen et al. (1969) state that the skin plays a minor role in EWL in Ostriches (Struthio camelus), contributing less than 2 percent of total evaporation at 400C. 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 (Phalaenoptilus nuttallii). 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).