Warmer, drier conditions linked to declining body condition in European robins, study finds
A 15-year study of European robins found that rising minimum temperatures and reduced soil moisture during the breeding season are associated with declining body condition, particularly in adult males and juveniles. Researchers used weather sliding-window analyses on data collected between 2007 and 2021 to identify critical time windows when environmental variables most strongly predicted individual body condition. The findings suggest climate-driven body condition decline could reduce juvenile survival and affect long-term population trends, though earlier fledging dates may partially offset these impacts.
A study published on bioRxiv tracked a European robin (Erithacus rubecula) population over 15 years (2007–2021) to examine how temperature, soil moisture, and vegetation productivity during the breeding season influence body condition across different age and sex groups. Using sliding-window analyses, researchers identified that body condition declined with increasing minimum temperatures in adult males and juveniles, and with low soil moisture in adults of both sexes. Over the full study period, adult male body condition during the post-fledging period showed a significant downward trend coinciding with rising minimum temperatures, while fledging dates advanced — a potential adaptive response. The study found no reliable critical time windows explaining short-term within-individual body condition changes over two-week intervals, suggesting that seasonal-scale rather than acute environmental variation drives the observed patterns. Importantly, lower body condition was associated with reduced apparent survival in juvenile robins, indicating potential demographic consequences for the population. The authors conclude that sex- and age-specific sensitivity to climate variables makes certain groups — especially adult males — more vulnerable to ongoing warming and drying trends.
What's missing
As a preprint, this study has not yet undergone formal peer review, so findings should be interpreted with caution. The study is limited to a single robin population, which may constrain generalizability to other populations or geographic regions. The authors note they could not identify reliable critical time windows for short-term within-individual body condition changes, leaving the mechanisms of rapid environmental effects unclear. The relationship between body condition and actual (rather than apparent) survival could not be fully disentangled, and the potential role of food availability (e.g., invertebrate prey) as a mediating variable between climate and body condition is not directly measured.
What different sources said
- bioRxivCenter
Sex- and age-specific body condition decline under warmer and drier breeding conditions in European robins
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