Unravelling the link between productivity and climate for two sympatric Acrocephalus warblers across Spain

ABSTRACT

Capsule

An accumulated rainfall of around 100 mm favoured the productivity of the specialist Moustached Warbler Acrocephalus melanopogon, but temperature had a negative effect. By contrast, temperature had a positive effect on the productivity of the generalist Reed Warbler Acrocephalus scirpaceus, whereas rainfall had almost no effect, although productivity also peaked when rainfall approached 100 mm.

Aims

Understanding the extent to which climate and geography are driving the negative trend of Moustached Warbler productivity, and the stable trend of Reed Warbler productivity.

Methods

Using data from a breeding bird monitoring ringing scheme in Spain (PASER; 1995 – 2021), we investigated the effects of seasonal rainfall and temperature patterns on the productivity of two sympatric warblers: the resident/short-distance migrant Moustached Warbler (occurring at nine ringing stations from a total of 129), and the generalist long-distance migrant Reed Warbler (57 out of 129 ringing stations). Analyses were performed using multi-adaptive regression splines (MARS).

Results

Between 1995 and 2021 geographical and site-specific factors drove annual productivity for both species, combined with rainfall and temperature. For the Moustached Warbler, geographical and site-related variables, together with the temporal changes (year), were more important than rainfall and temperature. For the Reed Warbler, temperature was more important than year but less than site and longitude.

Conclusion

Warmer temperatures and a higher frequency of torrential rainfall events may compromise the conservation of the vulnerable Moustached Warbler in Spain due to the adverse effect on productivity. In contrast, increasing temperatures across Spain may benefit the widely distributed Reed Warbler. Thus, Moustached Warbler populations are likely to decrease, whereas Reed Warbler populations might increase. However, further research is needed to establish the impact of climate change on survival, and its implications for the population trends and dynamics of these two sympatric warblers.

KEYWORDS:

• Bird conservation
• climate change
• passerines
• population dynamics
• population trends
• wetlands

Acknowledgements

The authors are grateful to Dr Ian Hartley, editor in chief of Bird Study, and the reviewers Catriona Morrison and an anonymous reviewer for their helpful comments, which improved the manuscript. We are also grateful to Chris Durdin from Honeyguide Wildlife Holidays for proofreading the manuscript. We thank the ‘Agencia Estatal de Metereología' for providing the climatic data and Carlos Mompó, Emilio Pons, Javi Cots and Mateo Ferrer for helping in the fieldwork. Furthermore, we extend our gratitude to SEO/BirdLife and Pedro Marín from the Gotur ringing group for generously providing the data. Lastly, we would like to acknowledge the invaluable contributions of numerous anonymous bird ringers who played a crucial role in data collection.

Disclosure statement

No potential conflict of interest was reported by the author(s).