Food deprivation influences dominance status in dark eyed juncos junco hyemalis
Animal Behaviour 43(1): 117-124
ISSN/ISBN: 0003-3472 DOI: 10.1016/s0003-3472(05)80077-6
Among gregarious birds, an individual's dominance status may influence its access to limited food resources and, consequently, its fat reserves during the non-breeding season. This study investigated whether food deprivation affected an individual's dominance status during encounters with conspecifics. In 45 dyads of dark-eyed juncos, one member was deprived of food for 4 h to reduce its stored fat level, thereby increasing its motivation to feed. Deprived juncos were dominant to their opponents significantly more often than were birds that had fed normally prior to the tests. When there was a measurable difference in fat reserves before food deprivation (16 dyads), the leaner individual was always dominant. Most dominance relationships remained unchanged for at least 24 h after food deprivation, but many dyads eventually reversed ranks when birds were introduced into a flock situation after 48 h. Dominance ranks in juncos may be established on the basis of an asymmetry in the value of a contested resource. Motivational asymmetries may be important determinants of dominance in the absence of large asymmetries in resource holding potential, and could have important ecological implications.