Aim: We explored the range shifts of alien and native birds, the responses of alien and native β-diversity to abiotic factors, and the effect of native diversity on alien β-diversity in two time periods.

Location: Great Britain.

Time period: 1968–1972, 2007–2011.

Taxa studied: Breeding birds.

Methods: We estimated range shifts of alien and native species between the periods 1968–1972 and 2007–2011. Following, β-diversity of alien and native communities was estimated by Jaccard pairwise index (β_tot) and partitioned into richness difference and replacement component for each period. We built abiotic Generalized Dissimilarity Models including abiotic factors for alien and native β_tot and their components and a biotic model for aliens including native taxonomic and functional diversity as predictors.

Results: Most alien and half native species expanded into new regions during the 40-year period. The native species range shifts did not exhibit a clear pattern along the longitudinal or latitudinal gradient, while alien species tended to move north-westwards. The richness difference was the dominant component of alien β-diversity, and the replacement component contributed mostly to native β-diversity. Alien β-diversity responded similarly, but less strongly than native β-diversity, to the abiotic gradients. Temperature-related variables, distance, and precipitation were the most important abiotic drivers of native and alien β-diversity. The biotic model of alien β-diversity explained more deviance than the abiotic model.

Main conclusions: Alien species expanded into new regions over the 40 years, with alien β-diversity driven mostly by species gains. The effect of environmental filtering on alien communities was weaker compared to native communities but was slightly reinforced in the second period compared to the first period, highlighting the role of environmental change in shaping diversity patterns. Native diversity played a key role in driving alien β-diversity, through biotic interactions or/and by reflecting climatic suitability or niche availability for aliens.

We explored the range shifts of alien and native breeding bird species of mainland Great Britain between the periods 1968–1972 and 2007–2011. We estimated β-diversity and its components (richness difference and replacement component) of alien and native communities per time period and explored the effect of abiotic factors (climate, land cover, human population, and elevation) on alien and native β-diversity and their components and of native diversity (species richness and functional diversity) on alien β-diversity by Generalized Dissimilarity Modelling. Breeding bird distribution data of Great Britain for the time periods 1968–1972 and 2007–2011 (data collected in hectads of 100 km²) were retrieved from The atlas of breeding birds in Britain and Ireland (Sharrock, 1976), Bird Atlas 2007–2011: the breeding and wintering birds of Britain and Ireland (Balmer et al., 2013), and Breeding and wintering bird distributions in Britain and Ireland from citizen science bird atlas (Gillings et al., 2019). Filtering of the species was applied based on their status that was retrieved from the British Trust for Ornithology's BirdFacts database (Robinson, 2005; https://www.bto.org/understanding-birds/birdfacts), Mcinerny et al. (2022), and Wayman et al. (2022). The trait dataset (body mass, clutch size, foraging location, habitat, activity time, and main diet) of breeding birds was retrieved from Tsianou et al. (2021). Specifically, the traits were compiled from datasets (Storchová et al., 2018) and electronic databases [Handbook of the Birds of the World Alive (https://www.hbw.com)]. Climatic factors (mean temperature, mean temperature range, mean temperature of the warmest month, mean temperature of the coldest month, and mean precipitation), percentage of different land cover types (forest, cropland, grassland, other, and, water), human population and elevation per hectad were calculated with using QGIS 3.18 using data available online. The detailed sources of abiotic factors are provided in the attached Readme.txt and the original paper, while the calculated variables are provided in attached .csv files (climaticA.csv, climaticC, HILDAA.csv, HILDAC.csv, human.popA.csv, human.popC.csv, elevation.csv). All analyses were performed using R version 4.1.0 (R Development Core Team 2021) and required packages are provided in the attached 1_Prepare environmental and diversity data.txt. Additional functions are provided in Nstar function.txt and Windrose function.txt. Species list (along with name changes), trait dataset, and hectads of mainland Great Britain are provided in the Species list.csv (name changes.csv), Traits.csv, and Mainland_GB.csv, respectively.  Scripts for performing analyses are provided in the 2_Estimate range shifts metrics.txt and 3_Run GDMs.txt. Instructions for performing analyses are provided in the Readme.txt.

References

• Balmer, D. E., Gillings, S., Caffrey, B., Swann, R., Downie, I., & Fuller, R. (2013). Bird Atlas 2007-11: the breeding and wintering birds of Britain and Ireland: BTO Thetford.
• Gillings, S., Balmer, D. E., Caffrey, B. J., Downie, I. S., Gibbons, D. W., Lack, P. C., ... & Fuller, R. J. (2019). Breeding and wintering bird distributions in Britain and Ireland from citizen science bird atlases. Global Ecology and Biogeography, 28(7), 866-874. https://doi.org/10.1111/geb.12906
• McInerny, C. J., Musgrove, A. J., Stoddart, A., Harrop, A. H., & Dudley, S. P. (2022). The British List: a checklist of birds of Britain (10th edition). Ibis, 164, 860–910. https://doi.org/10.1111/ibi.13065
• Robinson, R.A. (2005). BirdFacts: profiles of birds occurring in Britain & Ireland. BTO Research Report, 407, p.Thetford. (http://www.bto.org/birdfacts)
• Sharrock, J. T. R. (1976). The atlas of breeding birds in Britain and Ireland: A&C Black.
• Storchová, L., & Hořák, D. (2018). Life‐history characteristics of European birds. Global Ecology and Biogeography, 27(4), 400-406. https://doi.org/10.1111/geb.12709
• Tsianou, M. A., Touloumis, K., & Kallimanis, A. S. (2021). Low spatial congruence between temporal functional β‐diversity and temporal taxonomic and phylogenetic β‐diversity in British avifauna. Ecological Research, 36(3), 491-505. https://doi.org/10.1111/1440-1703.12209
• Wayman, J. P., Sadler, J. P., Pugh, T. A., Martin, T. E., Tobias, J. A., & Matthews, T. J. (2022). Assessing taxonomic and functional change in British breeding bird assemblages over time. Global Ecology and Biogeography, 31(5), 925-939. https://doi.org/10.1111/geb.13468

All data files can be opened and analyses can be performed using R software.