Data and scripts for analysis

Assortative mating based on consistent behavioural differences, or animal personality, is common in seabirds and may facilitate the selection of compatible partners. Personality such as boldness is often associated with foraging behaviours, including Individual For-aging Site Fidelity (IFSF)—the consistent use of specific foraging sites. Therefore, per-sonality-based mating may relate to mate choice based on foraging behaviour, potentially resulting in higher reproductive success. We investigated boldness and IFSF of streaked shearwaters (Calonectris leucomelas) breeding on Awashima Island, Japan. Boldness was assessed using a novel object test, and IFSF was quantified by tracking foraging routes with GPS loggers. We investigated the behavioural syndrome linking boldness and IFSF, the relationships of both boldness and IFSF within pairs, and the association be-tween boldness similarity and chick growth. We found a correlation between boldness and IFSF. Furthermore, individuals within pairs showed similarities in both boldness and IFSF, with boldness similarity enhancing chick growth rates. These findings suggest that boldness-based pairing may lead to shared degrees of IFSF, indicating that a partner’s boldness may provide insights into their foraging behaviour, resulting in well-matched pairs and higher chick growth rates. This study highlights the importance of personality in shaping foraging behaviour and reproductive strategies in seabirds.