Social status does not affect resting metabolic rate in wintering dark-eyed junco (Junco hyemalis).
Studies of wintering birds have demonstrated a correlation between social rank and energy expenditures. It is assumed that dominance is energetically costly because of increased activity, possibly caused by elevated androgen levels. As winter acclimatization leads to an increase in metabolic rate, maintaining dominance status in a cold climate can be a substantial challenge. We measured resting metabolic rates in dominant and subordinate dark-eyed juncos (Junco hyemalis) living in small groups in a controlled winter environment. We found no significant effect of social rank when controlling for body size. It has been shown previously that high testosterone levels during the nonbreeding season can lead to higher body conductance, fat loss, and higher nocturnal body temperature. A hypothesis explaining our result is that for juncos it is preferable to maintain low androgen levels during winter and to maintain social rank using a mechanism other than higher agonistic activity.
Vézina
F
F
Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada. fvezina@sfu.ca.
Thomas
D W
DW
D000378:Agonistic Behavior / Q000502:physiology; D000704:Analysis of Variance; D000818:Animals; D001481:Basal Metabolism; D001835:Body Weight; D003080:Cold Temperature; D005241:Feathers; D005247:Feeding Behavior / Q000523:psychology; D005260:Female; D008297:Male; D010101:Oxygen Consumption; D011792:Quebec; D011897:Random Allocation; D012621:Seasons; D012930:Social Dominance; D020308:Songbirds / Q000378:metabolism* / Q000502:physiology