Temperature Changes in Chimney Swifts (Chaetura pelagica) at Lowered Environmental Temperatures

Abstract

There are many references concerning torpor in the Chimney Swift (Chaetura pelagica). Storer (in Marshall 1960) stated that they can compensate for the great output of energy (required by their almost constant flight) by becoming torpid at night. McAtee (1947) gave many accounts of inactive swifts and stated that torpidity from brief to extended periods is possible, and that under favorable circumstances, hibernation seems a possibility. Berger (1961) stated that hibernation is known in Chimney Swifts. Lack (1956) referred to the discovery in December 1879 of a group of seven Chimney Swifts stowed away in an unused stove pipe in New York state. Hypothermia and hibernation have been found in other species of swifts and in related birds. Koskimies (1948) found that European Swifts (Apus apus) became temporarily poikilothermic, or torpid, when deprived of food. White-throated Swifts (Aeronautes saxatalis) have been shown to become torpid when exposed to both cold and starvation (Bartholomew et al. 1957). Members of various genera of hummingbirds (Pearson 1950, 1953; Howell and Dawson 1954; Lasiewski 1963) and Poorwills, Phalaenoptilus nuttallii (Bartholomew et al. 1957; Howell and Bartholomew 1959, and references cited therein), exhibit true hibernation with hypothermia. Lesser Nighthawks, Chordeiles acutipennis (Marshall 1955), and colies, Colius (Huxley et al. 1939), apparently become torpid. With this background of reports of torpor in the Chimney Swift and of the demonstration of hypothermia among its relatives, the present study was undertaken to determine whether the body temperature of the Chimney Swift changes during periods of lowered environmental temperatures.