Convective rainfall drives behavioral shifts across multiple foraging scales in breeding seabirds

Background Seabird foraging behaviors may be influenced not only by the direct adverse effects of rainfall (e.g., limitations on flight) but also by indirect effects—either adverse or beneficial—such as changes in prey distribution. To understand the multifaceted impacts of rainfall and their ecological significance, it is essential to examine foraging behavior across multiple spatiotemporal scales. In particular, assessing the effects of altered convective rainfall patterns—localized and shorter-lived events that have become increasingly frequent due to recent rapid temperature increases—is crucial for predicting future behavioral shifts in seabirds. Methods We investigated the relationships between multiple climatic factors—including two types of rainfall (convective and large-scale rainfall), cloud cover, and wind speed—and three spatiotemporally distinct aspects of foraging behavior, as well as chick growth, in streaked shearwaters Calonectris leucomelas rearing chicks on Awashima Island, Japan, from 2011 to 2024. Specifically, we focused on fine-scale behavioral states—traveling, foraging, and resting—estimated using a Hidden Markov Model; meso-scale trip parameters, including maximum distance and duration of each foraging trip; broad-scale behavioral specialization, quantified as Individual Foraging Site Fidelity (IFSF); and chick growth rate as a proxy for foraging outcomes. Results Increased convective rainfall was associated with increased transition probabilities from traveling to foraging states, higher stationary probabilities of foraging states, longer foraging trip durations, and higher IFSF. Additionally, cloud cover and wind speed were associated with fine-scale behavioral states and meso-scale trip parameters. While increased large-scale rainfall was associated with higher IFSF, no clear associations were found between climatic factors and chick growth rate. Conclusions Seabirds engaged in more active prey searching during convective rain events, which prolonged foraging trips, and successful foraging experiences during these periods increased IFSF. We propose that fine-scale behavioral changes induced by convective rain, likely driven by increased prey availability, can cascade into broader-scale behavioral patterns. Our findings contributes to a comprehensive understanding of climate-induced changes in seabird foraging behavior by focusing on behavior across multiple spatiotemporal scales.