Data and code from: Bergmann’s rule: Why does body size increase with latitude?

Bergmann’s rule describes the tendency for endothermic body size to increase with latitude, a pattern often attributed to climatic factors. However, the underlying developmental and evolutionary mechanisms remain debated. Latitudinal gradients in temperature and precipitation are often thought to be responsible for Bergmann’s rule, but climate may generate such geographical patterns via several alternative pathways. We examined geographic patterns in body size of 5,596 burrowing owls (Athene cunicularia) throughout western North America to inform the underlying processes responsible for range-wide phenotypic variation. Burrowing owls followed Begmann’s rule, with larger individuals in northern latitudes. We also detected a longitudinal gradient, with the largest owls in the northwest of the breeding range. We considered several mechanisms to explain geographic gradients in burrowing owl body size: developmental plasticity, reversible plasticity, and local adaptation. Developmental plast..., , # Data and code from: Bergmann’s rule: Why does body size increase with latitude?

Dataset DOI: [10.5061/dryad.7m0cfxq9h](https://doi.org/10.5061/dryad.7m0cfxq9h)

## Description of the data and file structure

This dataset and associated R Markdown code accompany the study \"Bergmann's Rule: Why does body size increase with latitude?\" Leveraging an extensive morphometric dataset of 5,597 burrowing owls (*Athene cunicularia*) sampled across the western United States (2000–2020), we examined the environmental mechanisms driving continental body size gradients. We analyzed body mass (juveniles and adults), wing chord, and tarsus length in relation to four climatic variables: drought, temperature, precipitation, and primary productivity. These variables were evaluated across multiple temporal scales (acute, one-year lagged, and long-term) using linear mixed-effects models that accounted for variation among years and sampling sites. This approach allowed us to evaluate patterns consistent wi...,