Status signalling in dark eyed juncos junco hyemalis plumage manipulations and hormonal correlates of dominance
Holberton, R.L.; Able, K.P.; Wingfield, J.C.
Animal Behaviour 37(4): 681-689
ISSN/ISBN: 0003-3472 Accession: 007817968
Status signalling in dark-eyed juncos was investigated by using plumage mainpulations and observing interactions within pairs of birds. Plumage manipulations included darkening of the hood and mantle and the addition of white tail feathers to mimic the appearance of adult males. Plumage characteristics predicted dominance relationships within pairs of first-year males when body size and prior residence in cages was controlled. These characteristics were also strong enough to reverse previously established intra-class relationships within pairs of first-year males and first-year and adult females. The results fail to support the incongruence hypothesis (Rohwer: Behaviour, 1977, 61, 107-129; Rohwer and Rohwer: Anim. Behav., 1978, 26, 1012-1022). In contrast to recent studies using exogenous testosterone to investigate dominance behaviour, circulating plasma levels of testosterone were measured and a comparison made between those of dominants and those of subordinates. Plasma levels of corticosterone were also analysed as a measure of stress. No correlation between either hormone and dominance status was found. Hypotheses are proposed to explain the absence of a relationship between circulating levels of testosterone and winter aggression in flocking birds.