The physiology of hypothermia in the black-capped Chickadee,Parus atricapillus
- 226 Downloads
The shivering, body temperature, and metabolic response to stable and decreasing ambient temperature were measured in winter acclimatized Black-capped Chickadees,Parus atricapillus. Shivering activity, measured by duration and amplitude of bursts, increased curvilinearly from thermoneutral temperatures of 27°C down to 0°C. This parabolic shivering response may be a major component of the curvilinear response of metabolism to decreasing ambient temperature.
Birds exposed to 0°C exhibited metabolism 32–45% lower than predicted for a 12-g homeotherm and body temperatures 10°C below the pre-experimental nocturnal body temperature. This hypothermia was not the result of a breakdown in thermoregulation, but was a controlled effort serving to reduce overnight energy expenditure. It is suggested that (1) hypothermia was achieved by decreased shivering by pectoral muscles during exposure to decreasing ambient temperatures, (2) the rate of body temperature decline was moderated by intermittent and reduced bursts during the cooling period, and (3) body temperature was maintained at a particular level during exposure to a stable low ambient temperature by intense bursts lasting one to three minutes.
The physiology of hypothermia in chickadees is similar to torpor; however, chickadees did not arouse to a normal diurnal body temperature in the laboratory, and their hypothermia was not induced by inanition or prolonged exposure to cold, as reported for other species capable of torpor.
KeywordsEnergy Expenditure Ambient Temperature Human Physiology Body Temperature Prolonged Exposure
Unable to display preview. Download preview PDF.
- Aschoff, J., Pohl, H.: Rhythmic variations in energy metabolism. Fed. Proc. Fed. Amer. Soc. Exp. Biol.29, 1541–1552 (1970)Google Scholar
- Austin, G.T., Bradley, W.B.: Additional responses of the poorwill to low temperatures. Auk86, 717–725 (1969)Google Scholar
- Bartholomew, G.A., Howell, T., Cade, T.J.: Torpidity in the white-throated swift, anna humming-bird, and poorwill. Condor59, 145–155 (1957)Google Scholar
- Bartholomew, G.A., Hudson, J.W., Howell, T.: Body temperature, oxygen consumption, evaporative heat loss, and heart rate in the poorwill. Condor64, 117–125 (1962)Google Scholar
- Brooks, W.S.: Comparative adaptations of the Alaskan redpolls to the arctic environment. Wilson Bull.80, 253–280 (1968)Google Scholar
- Calder, W.A., King, J.R.: Thermal and caloric relations of birds. In: Avian biology, Vol. IV (Farner, D.S., King, J.R., eds.) New York: Academic Press 1974Google Scholar
- Carpenter, F.L.: Torpor in an Andean hummingbird: its ecological significance. Science183, 545–547 (1974)Google Scholar
- Chaplin, S.B.: Daily energetics of the black-capped chickadee,Parus atricapillus, in winter. J. comp. Physiol.89, 321–330 (1974)Google Scholar
- Cheke, R.A.: Temperature rhythms in African montane sunbirds.Ibis113, 500–506 (1971)Google Scholar
- Dawson, W.R., Fisher, C.D.: Responses to temperature by the spotted nightjar (Eurostopodus guttatus). Condor71, 49–53 (1969)Google Scholar
- Dawson, W.R., Hudson, J.W.: Birds. In: Comparative physiology of thermoregulation, Vol. I (Whittow, G.C., ed.). New York: Academic Press 1970Google Scholar
- Haftorn, S.: Hypothermia of tits in the arctic winter. Ornis Scand.3, 153–166 (1972)Google Scholar
- Hart, J.S.: Seasonal acclimatization in four species of small wild birds. Physiol. Zool.35, 224–236 (1962)Google Scholar
- Hensel, H.: Neural processes in thermoregulation. Physiol. Rev.53, 948–1017 (1973)Google Scholar
- Lasiewski, R.C., Dawson, W.R.: Physiological responses to temperature in the common nighthawk. Condor66, 477–490 (1964)Google Scholar
- Lasiewski, R.C., Weathers, W.W., Bernstein, M.H.: Physiological responses of the giant hummingbird,Patagona gigas. Comp. Biochem. Physiol.23, 797–813 (1967)Google Scholar
- MacMillen, R.E., Trost, C.H.: Nocturnal hypothermia in the inca dove,Scardafella inca. Comp. Biochem. Physiol.23, 243–253 (1967)Google Scholar
- Mugaas, J.N., Templeton, J.R.: Thermoregulation in the red-breasted nuthatch (Sitta canadensis). Condor72, 125–132 (1970)Google Scholar
- Snedecor, G.W. Cochran, W.G.: Statistical methods. 6th ed. 593 pp. Ames: Iowa State Press 1967Google Scholar
- Steen, J., Enger, P.S.: Muscular heat production in pigeons during exposure to cold. Amer. J. Physiol.19, 157–158 (1957)Google Scholar
- Steen, J.: Climatic adaptation in some small northern birds. Ecology39, 625–629 (1958)Google Scholar
- West, G.C.: Shivering heat production in wild birds. Physiol. Zool.38, 111–119 (1965)Google Scholar
- Wolf, L.L., Hainsworth, F.R.: Environmental influence on regulated body temperature in torpid hummingbirds. Comp. Biochem. Physiol.41, 167–174 (1972)Google Scholar