Multidimensionality of fear in captive greenfinches (Carduelis chloris)

Covariation of individual responses to different fear-eliciting situations is expected to manifest in general “fearfulness syndrome.” We tested for the existence of such a syndrome in wild-caught captive greenfinches. We assessed the propensity to give distress calls at handling, latency to feed at the presence of a predator image, and changes in locomotor activity in response to distress calls of conspecifics. Additionally, we measured the frequency of flapping flight movements against cage bars and tendency to damage tail feathers in captivity as indicators of the ability of birds to cope with captive conditions. As a proxy of neuroendocrine activity (an expected covariate of fearfulness), we measured the amount of stress hormone corticosterone deposited into feathers grown during captivity. All the behavioral traits were individually repeatable in time, but there were no correlations between them. Lack of the behavioral syndrome for fearfulness was also revealed by structural equation modelling. The findings of this experiment challenge the concept of a single internal variable responsible for fearfulness and support the proposed multidimensional nature of fear responses.