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Patterns and dynamics of rest-phase hypothermia in wild and captive blue tits during winter.

  • Andreas Nord
  • Johan Nilsson
  • Maria Sandell
  • Jan-Åke Nilsson
Publishing year: 2009
Language: English
Pages: 737-745
Publication/Series: Journal of Comparative Physiology B
Volume: 179
Document type: Journal article
Publisher: Springer

Abstract english

We evaluated biotic and abiotic predictors of rest-phase hypothermia in wintering blue tits (Cyanistes caeruleus) and also assessed how food availability influences nightly thermoregulation. On any given night, captive blue tits (with unrestricted access to food) remained largely homeothermic, whereas free-ranging birds decreased their body temperature (T (b)) by about 5 degrees C. This was not an effect of increased stress in the aviary as we found no difference in circulating corticosterone between groups. Nocturnal T (b) in free-ranging birds varied with ambient temperature, date and time. Conversely, T (b) in captive birds could not be explained by climatic or temporal factors, but differed slightly between the sexes. We argue that the degree of hypothermia is controlled predominantly by birds' ability to obtain sufficient energy reserves during the day. However, environmental factors became increasingly important for thermoregulation when resources were limited. Moreover, as birds did not enter hypothermia in captivity when food was abundant, we suggest that this strategy has associated costs and hence is avoided whenever resource levels permit.


  • Biological Sciences


  • Centre for Animal Movement Research
  • ISSN: 0174-1578
Andreas Nord at NHM London
E-mail: andreas [dot] nord [at] biol [dot] lu [dot] se


Evolutionary ecology

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