This file contains data from Mainwaring & Street (2021), "Conformity to Bergmann’s rule in birds depends on nest design and migration", Ecology and Evolution, for 518 species of Western Palaearctic birds. The dataset contains the following 8 columns: 'Species': species' binomial names 'Body_mass': species' mean body mass, in grams 'Nest_design': species' typical nest classification based on both nest structure and location, either 'open', 'semi' or 'closed' 'Nest_location': species' typical nest location, either 'open', 'semi-hole' or 'hole' 'Nest_structure': species' typical nest structure, either 'open' or 'closed' 'Migration': species' typical migratory behaviour, either 'resident', 'short distance' or 'long distance' 'Latitude': species' breeding latitude, in degrees 'bio10_mean': mean temperature of the warmest quarter of species' breeding ranges, in degrees Celsius The dataset contains only species for which we have complete data on body mass, nest design, migration, and either latitude or temperature, and which are included in the associated phylogeny. 5 species are missing data for latitude and 3 for temperature (indicated with 'NA'). For full details on data collection and processing, please see the Methods section of the associated manuscript.