CORNELIUS, J.M.; BREUNER, C.W.; HAHN, T.P.; Univ. of California, Davis; Univ. of Texas, Austin; Univ. of California, Davis: Effects of food reduction on stress reactivity in an irruptive nomad, the red crossbill

Many animals time their migratory movements seasonally in order to exploit an abundant but temporary food source. Some opportunists specialize on food sources that are abundant and temporary, but are not consistently distributed in either space or time. One problem these animals face is deciding when to leave an existing but declining food source in search of a newly developing food source. One hypothesis is that an increase in stress reactivity may occur in opportunists in response to declining food supply, thereby facilitating the behavioral transition into a nomadic state. We studied captive red crossbills (Loxia curvirostra), a nomadic bird that specializes on conifer seeds, to determine if a decline in food availability affects stress reactivity. Experimental birds restricted for 94 hours to 75% of normal daily food intake had higher maximum free corticosterone (CORT) levels during a standard handling stress protocol than they had prior to food restriction (repeated measures ANOVA, p<0.05). Control birds received ad libitum food throughout the experiment and showed no significant changes in maximum free CORT levels. Baseline CORT levels and amount of corticosterone binding globulins did not change significantly after treatment in either experimental or control groups. The results of this study support our hypothesis and suggest that further research regarding the role of the stress system in irruptive and nomadic behavior may be illuminating.