Ochi, D.; Oka, N.; Watanuki, Y.

Behavioral coordination between mated pairs plays a critical role in the reproductive success of many species practicing bi-parental care. In pelagic seabirds such coordination may help cope with the challenges posed by spatially heterogeneous and limited food availability. This study investigated the relationship between parental coordination and reproductive performance by analyzing nest attendance patterns of breeding pairs of the Streaked Shearwater Calonectris leucomelas during the chick-rearing period on Mikura Island, Japan. Using an automated identification system, we recorded nest attendance and quantified coordination levels through the {varphi} coefficient. Our analysis revealed that higher coordination levels were associated with reduced extended nest absence periods, potentially decreasing prolonged chick fasting. However, coordination levels showed no significant direct effect on chick growth rates, while regular provisioning frequency, which can be associated with the coordination, and meal size emerged as critical determinants of chick development. These findings indicate that, in Streaked Shearwaters, behavioral coordination during chick rearing contributes to indirect effect on chick development, and also, might reduce the duration of unguarded periods at the nest.