Temporal Changes in the Climatic Predictors of Hatching Success in Leach's Storm‐Petrels

ABSTRACT

Climate change is rapidly altering ecosystems worldwide and can modify the demographic rates of long‐lived vertebrates. For seabirds, which rely on ocean productivity, reproductive success is particularly sensitive to climatic variability. Identifying the scale and stability of climate drivers is therefore critical for predicting population dynamics. Previous work on Leach's storm‐petrels ( Hydrobates leucorhous ) breeding on Kent Island, New Brunswick, showed that Annual Global Mean Temperature (AGMT) best explained hatching success between 1955 and 2010, with a nonlinear response peaking in the late 1980s. Here, we extend this dataset through 2024 to test whether AGMT remains a reliable predictor given the recent rise of ocean temperatures. Using mixed‐effects models, we compared hatching success with multiple climatic indices at regional, basin, and global scales. While AGMT retained some explanatory power, the best performing model for predicting variation in hatching success for the historical dataset (1955–2010) also included the Southern Oscillation Index (SOI), which was not evaluated in the original analyses, and the Atlantic Multidecadal Oscillation (AMO) for the full dataset (1955–2024). Different pathways may be involved: SOI could reflect non‐breeding conditions and have a carry‐over effect, whereas AMO could change prey availability and foraging conditions during egg formation and incubation. The relationships of hatching success with environmental indices changed over time. These results provide evidence that climate–biology relationships can be temporally dynamic, with the effects of some climatic drivers on hatching success changing over the study period. The AMO has also been linked to variation in adult survival for this population; its emerging importance for hatching success implies a compounded demographic impact with consequences for the population vulnerability.