Low corticosterone response Florida scrub-jays (Aphelocoma coerulescens) react more aggressively to territorial call playback (#261)
Studies of female vocal behaviour and female aggression in birds have lagged behind those of more conspicuously aggressive males. While the gap has recently begun to close, much work remains to be done, especially in temperate species. In the Florida scrub-jay (Aphelocoma coerulescens; FSJ) both males and females defend their territory year-round, with females predominantly using a sex-specific “rattle” call. We conducted simulated territorial intrusions using playback of male and female FSJ vocalizations to breeding pairs during the 2014 and 2015 breeding and post-breeding seasons. Aggression scores were elevated in both sexes during the breeding season over post-breeding, and males and females responded equally aggressively regardless of the sex of the simulated intruder. Behavioural traits, like aggression, often correlate with physiological profiles, such as the corticosterone (CORT) response. All FSJs on site have been subjected to a capture-restraint protocol to assess their stress-induced CORT (SI-CORT) response, a physiological trait that our research finds to be repeatable across most, if not all, of an individual's life. We found a statistically significant (p = 0.025), albeit relatively weak (r2 = 0.122), negative relationship between aggression scores and SI-CORT. However, males did not exhibit elevated CORT levels following simulated intrusions, suggesting that territorial encounters are relatively 'low-stress' events that are independent of the HPA axis. We will discuss the potential fitness consequences of the links between the CORT response and behavioral phenotypes.