Body Temperature, Oxygen Consumption, Evaporative Water Loss, and Heart Rate in the Poor-Will

Abstract

The physiology of the Poor-will (Phalaenoptilus nuttallii) is of unusual interest. Not only is it one of the very few birds which can undergo long periods of dormancy comparable in most respects to mammalian hibernation, but over much of its summer range it is exposed to severe conditions of heat because of its habit of spending the daylight hours, even in the desert, sitting quietly in the open. During the past year we have had the opportunity to make a series of observations on two captive, adult PIoor-wills, one (P. n. hueyi) captured by Mr. Donald Schroeder in the Coachella Valley, Riverside County, California, and the other (P. n. californicus) found in a torpid condition in Eagle Rock, Los Angeles County, California, by Mrs. Gerald Massey. Both birds were maintained for many months in captivity and were fed on a diet of meal worms (Tenebrio larvae) and canned cat food. The limited information on the physiology of Poor-wills has previously been summarized (Bartholomew, Howell, and Cade, 1957; Howell and Bartholomew. 1959) and need not be reviewed here.