Abstract Consistent individual differences in behavior are often expressed as personality. One such trait, boldness—reflecting an individual’s propensity to take risks—can be associated with Individual Foraging Site Fidelity (IFSF), the degree to which an individual repeatedly uses the same foraging site. In seabirds, within-pair correlations in boldness and foraging specialization may shape parental effort, enhancing reproductive success and sustaining among-individual variation. These observations suggest that a behavioral syndrome linking boldness and IFSF may manifest at the pair level as within-pair correlations across behavioral contexts; however, no study has simultaneously examined behavioral syndromes and within-pair correlations. We investigated boldness and IFSF in streaked shearwaters ( Calonectris leucomelas ) breeding on Awashima Island, Japan. Boldness was assessed using a novel object test, while IFSF was quantified through GPS tracking of foraging routes. We evaluated the boldness-IFSF syndrome, within-pair correlations in boldness and IFSF, and whether boldness similarity predicts chick growth. We found a correlation between boldness and IFSF, and partners were similar in both traits. Moreover, greater within-pair similarity in boldness was positively associated with chick growth rate. These findings could arise through three non-mutually exclusive mechanisms: adaptive partner selection, post-pairing behavioral adjustment, and non-adaptive partner selection driven by confounding factors. We could not demonstrate assortative mating based on behavioral traits or identify the mechanisms by which within-pair similarity might influence reproductive success. Nevertheless, our findings underscore the importance of within-pair behavioral correlations and highlight the value of integrating these previously distinct concepts to facilitate new discoveries.
Takeda et al. (Thu,) studied this question.