Reproductive flexibility in a single‐brooded migrant: can the European roller "Coracias garrulus" adapt to extreme weather events?

Abstract

Global climate change has intensified extreme weather events, including short-duration but intense rainfall, which can significantly impact avian reproduction. This study examines the effects of extreme rainfall on the reproductive phenology and performance of the European roller Coracias garrulus, a single-brooded migratory bird, in a semiarid ecosystem. We analysed breeding parameters during 2023, characterised by exceptionally intense and concentrated rainfall, and compared them with long-term data (2006–2024). Our results indicate that breeding phenology in 2023 exhibited significant shifts. Rollers initiated egg-laying approximately five days earlier than the long-term average in the early breeding season, while late-season laying was delayed by approximately 11 days. The prolonged breeding season was marked by a high incidence of breeding failures, particularly during incubation. Moreover, we observed an unprecedented surge in apparent replacement breeding attempts, a rare phenomenon in this single-brooded species. Despite these challenges, overall population productivity remained consistent with long-term averages because successful breeding was heavily concentrated in resilient nest substrates, nest boxes and sandstone burrows, which buffered the weather's impact and compensated for catastrophic failures in stone cavities. Our findings underscore the European roller's capacity for reproductive flexibility, but also suggest the significant fitness costs and constraints associated with these adaptive responses. These results highlight the need for conservation strategies that consider climate-induced phenological shifts and the importance of nest box designs optimised to mitigate the interacting adverse effects of extreme rainfall and subsequent heatwaves.