Quantifying personality of wild birds: contrasting two mobile field assays

When species co-occur, behavioral differences between them may dictate the outcome of ecological and reproductive interactions. Exploratory behavior is an ecologically relevant measure of personality associated with speed-accuracy tradeoffs. Behavioral differences between species coming into contact could affect mate choice and social dominance relationships, ultimately determining where they occur and whether they hybridize. We measured exploratory behavior in wild Carolina (Poecile carolinensis) and Black-capped (P. atricapillus) chickadees, as well as their hybrids, in the field using two different mobile assays: a screen tent used during a pilot study, and a wooden, illuminated box designed to reduce outside influences. We scored exploratory behavior for both assays by recording variables describing activity and latency to reach different sections within the chamber, and then produced a composite score using principal components analysis. Within each species, individuals exhibited a wide range of exploratory scores, but black-capped, Carolina, and hybrid chickadees did not differ in mean scores for either assay. The box and tent scores did not correlate, suggesting that these assays are not measuring the same behavior. Tent score was nearly repeatable (n = 14, p = 0.059; r = 0.52). The box score was highly repeatable (n = 28, p < 0.001; r = 0.62), suggesting that box score represents individual personality and that the box successfully reduced outside influences. Most of the variation exists between individuals, not species, suggesting that these sister species display high behavioral overlap. Behavioral similarity may play a role in these species’ willingness to hybridize in the wild.