Results/Conclusions
Males had a significantly greater proportion of crown whiteness than females (t=3.354, df=491, p=0.001). There was no significant difference in number of fledglings for crown manipulated males. MWCS males received simulated territorial intrusions by a mounted decoy (each twice to the same decoy, both ‘white-enhanced’ and ‘white-diminished’ crown treatments; presented in random order on different days). Males responded with significantly increased alarm rates when presented with white-enhanced decoys (Rates of Chink-calls 2008 [Wald Chi-square=7.233, df=1, p=0.007], Rates of Chink-calls 2009 [Wald Chi-square=7.733, df=1, p=0.005], and body puffs 2009 (Wald Chi-square=4.857, df=1, p=0.028). MWCS males representing the top 25% of whitest crowns within the population had a significantly lower change in corticosterone response than the rest of the population following a standard stress series test (t = -2.654, df = 30.63, p-value = 0.01250). Thus birds with whiter crowns draw consistently stronger alarm responses from conspecific territory holders supporting the social punishment hypothesis, yet they are better adapted to limit stress response and maintain breeding activity during their short breeding season. Social tradeoffs are therefore at least partially responsible for the honesty of crown whiteness as a signal of status in male MWCS and may be influenced by sexual selection.