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Journal of Comparative Physiology A

, Volume 185, Issue 5, pp 463–470 | Cite as

Energy metabolism, testosterone and corticosterone in white-crowned sparrows

  • M. Wikelski
  • S. Lynn
  • J. C. Breuner
  • J. C. Wingfield
  • G. J. Kenagy
ORIGINAL PAPER

Abstract

The influence of the steroid hormones testosterone and corticosterone on energy metabolism and activity of birds is largely enigmatic. We measured resting metabolic rate during night and day in 12 long-term castrated and 12 intact male white-crowned sparrows (Zonotrichia leucophrys gambelii) under short-day (8:16 SD), long-day (20:4 LD), LD+testosterone implant and LD−testosterone implant conditions. Each male was sequentially measured under all four conditions. Photostimulation increased testosterone, resting metabolic rate, food intake, hopping activity and body mass in castrates and intact males. Surprisingly, testosterone levels and metabolic rates did not differ between intact and castrated males. Testosterone implantation increased activity and food intake, but decreased body mass and resting metabolic rate in both groups. Removing testosterone implants reversed the effects on resting metabolic rate, activity and food intake. Corticosterone levels, measured immediately at the end of metabolism measurements, showed birds were not stressed. Corticosterone had no apparent relationship with resting metabolic rate and there was no interaction between corticosterone and testosterone. Overall, positive changes in testosterone levels resulted in a decrease of resting metabolic rate. We speculate that testosterone increases activity, and birds compensate for increased activity metabolism by reducing resting metabolic rate.

Key words Metabolism White-crowned sparrows Testosterone Corticosterone Activity 
AbbreviationsBMR basal metabolic rate D duration of subjective night L duration of subjective day RMR resting metabolic rate T testosterone 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1999

Authors and Affiliations

  • M. Wikelski
    • 1
  • S. Lynn
    • 1
  • J. C. Breuner
    • 1
  • J. C. Wingfield
    • 1
  • G. J. Kenagy
    • 1
  1. 1.Department of Zoology, Box 351-800, University of Washington, Seattle, Washington 98195, USAUS

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