Motivation Birds are an extremely diverse group in terms of adaptations to environmental conditions, which is reflected in their life histories and ecological traits. Recently, functional aspects of avian diversity have been used frequently in comparative analyses as well as in community ecology studies; thus, open access to complete datasets of traits will be valuable. We focused on European bird species and compiled information about crucial ecological traits. This dataset is thus useful for research investigating large‐scale patterns in European avifauna and can be used in various analyses in evolutionary ecology, macroecology or conservation biology. Main types of variables contained We chose several types of avian traits, such as morphological (e.g., weight, wing, bill or tarsus length), reproductive (e.g., clutch size, egg mass, incubation period or type of young) and behavioural traits (type of nest, mating system or type of parental care), dietary (e.g., folivore, granivore, insectivore or carnivore) and habitat preferences (e.g., deciduous/coniferous forest, reed or grassland). Spatial location and grain Europe; all breeding bird species (n = 499). Major taxa and level of measurement In total, we created a dataset for 499 bird species breeding in Europe and 34 key life‐history traits represented in 85 variables. As a primary source of information we used the comprehensive handbook The birds of the Western Palearctic. The traits provide information about species‐specific mean values. We did not record values for different geographical subspecies (i.e., the trait value always represents the average for the whole breeding area of a particular species). Software format The data file is in ASCII text, tab delimited, not compressed.

Environmental change has reshuffled communities often causing taxonomic homogenization rather than differentiation. Some studies suggest that this increasing similarity of species composition between communities is accompanied by an increase in similarity of trait composition—functional homogenization—although different methodologies have failed to come to any consistent conclusions. Functional homogenization could have a large effect on ecosystem functioning and stability. Here, we use the general definition of homogenization as “reduced spatial turnover over time” to compare changes in Simpson's beta diversity (taxonomic turnover) with changes in Rao's quadratic entropy beta diversity (functional turnover) in British breeding birds at three spatial scales. Using biotic and climatic variables, we identify which factors may predispose a site to homogenization. The change in turnover measures between two time periods, 20 years apart, was calculated. A null model approach was taken to identify occurrences of functional homogenization and differentiation independent of changes in taxonomic turnover. We used conditional autoregressive models fitted using integrated nested Laplace approximations to determine how environmental drivers and factors relating to species distributions affect changes in spatial turnover of species and functional diversity. The measurement of functional homogenization affects the chance of rejection of the null models, with many sites showing taxonomic homogenization unaccompanied by functional homogenization, although occurrence varies with spatial scale. At the smallest scale, while temperature‐related variables drive changes in taxonomic turnover, changes in functional turnover are associated with variation in growing degree days; however, changes in functional turnover become more difficult to predict at larger spatial scales. Our results highlight the multifactorial processes underlying taxonomic and functional homogenization and that redundancy in species traits may allow ecosystem functioning to be maintained in some areas despite changes in species composition.

No abstract