Data for: Recent changes in thermal niche position and breadth of bird assemblages in Spain in relation to increasing temperatures

The dataset is a dataframe that comprises the Community Thermal Indices (response variable) and the environmental and geographic variables employed as predictors of the spatial GLMM. This model related the temperatures to the changes of CTI, considering the habitat (forest) change. The Community Thermal Indices were computed from the Species Thermal Indices. We obtained four thermal indices for each species (Species Thermal Index – STI) by combining the global species’ distribution and the climate information. The STI1 (i) shows the mean temperature of the breeding season (April-July) throughout the species’ distribution range. Similarly, the STI2 (ii) is the average of the maximum temperatures above the percentile 95 in July, and the STI3 (iii) is the average minimum temperature below the percentile 05 in April in the species’ breeding distribution range. These three indices represent a species’ thermal affinity. On the other hand, the fourth index (iv) (Species Thermal Range - STR) represents the average thermal range (April-July) throughout the distribution area and can be understood as species thermal breadth. It is computed as STI3-STI2. We calculated a set of community thermal indices (CTI) for the assemblage of bird species in each of the 10x10km UTM grid squares of each of the breeding bird atlases. We obtained four different CTIs: CTI1, CTI2, CTI3, and CTR. The first three were calculated as the average of the STI, STI2, and STI3 of the species present in the assemblage, respectively. The CTR (Community Thermal Range) is based on the average temperature range of the species (STR) that make up the assemblage and thus informs on the average niche breadth (Gaget et al., 2020). We calculated CTIs for each of the four-year periods covered by the atlases. The dataset also includes the standardized and unstandardized local temperature (ºC) and forest cover (ha) for each grid square and for each breeding bird atlas. It also includes the standardized and unstandardized coordinates of each grid square in decimal degrees (WGS84). Local temperatures were obtained from Chelsa (v.2.1., Karger et al., 2017), averaging data for each five-year sampling period in each square. We used the CORINE Land Cover Accounting Layers built for the years 2000 and 2018, to link forest cover with the community indices for the first and second sampling periods, respectively

[Aim] Animal communities around the world are responding to climate change by al-tering their taxonomic composition, mainly through an increase in the colonisationrate of warm-dwelling species and the local extinction of cold-dwelling ones. We as-sessed whether the taxonomic composition of bird assemblages in peninsular Spainhas changed in accordance with the recent increase in temperature. We also evalu-ated the role of species thermal affinities and population dynamics on these changes.

[Location] Peninsular Spain.

[Taxon] Birds.

[Methods] We compared assemblages reported in the last Spanish breeding bird at-lases (1998–2002 vs. 2014–2018) in 10 × 10 km squares. We described species' ther-mal niches by overlaying global species breeding distributions and world temperaturemetrics (based on mean, minimum, maximum and range), and then aggregated themto obtain a set of community thermal indices for each assemblage (CTIs and CTR forranges). Long-term average temperatures and local current temperatures were relatedto changes in CTIs using spatial GLMMs, which considered habitat change. We identi-fied the species most responsible for variation in assemblages and regressed species'influence on thermal affinities and population dynamics.Results: CTIs increased with temperature and warm-dwelling species became moreprevalent to the detriment of cold-dwelling ones. However, we found a counteract-ing effect of temperature and habitat. Cold-dwelling forest species were among themost influential species, mainly through colonisation, while warm-dwelling farmlandspecies contributed through local extinctions (both attenuated local increases in CTI).The mean thermal breadth of assemblages (CTR) decreased with temperatures.Main conclusions: The taxonomic composition of bird assemblages shifted in line withthe main expectations due to global change (thermophilisation), mainly due to localcolonisation of warm-dwelling species, although it did not show the pattern of ther-mal homogenisation suggested elsewhere. Our results add further evidence of theinterplay between climate warming and land-use change in the ongoing adjustment ofanimal communities.

Peer reviewed