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

Aim: Animal communities around the world are responding to climate change
by altering their taxonomic composition, mainly through an increase in the
colonisation rate of warm-dwelling species and the local extinction of
cold-dwelling ones. We assessed whether the taxonomic composition of bird
assemblages in peninsular Spain has changed in accordance with the recent
increase in temperature. We also evaluated the role of species'
thermal affinities and population dynamics in these changes. Location:
Peninsular Spain. Taxon: Birds. Methods: We compared assemblages reported
in the last Spanish breeding bird atlases (1998–2002 vs 2014–2019) in
10x10 km squares. We described species’ thermal niches by overlaying
global species breeding distributions and world temperature metrics (based
on mean, minimum, maximum and range), and then aggregated them to obtain a
set of community thermal indices for each assemblage (CTIs, and CTR for
ranges). Long-term average temperatures and local current temperatures
were related to changes in CTIs using spatial GLMMs, which considered
habitat change. We identified 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 more prevalent to the detriment of
cold-dwelling ones. However, we found a counteracting effect of
temperature and habitat. Cold-dwelling forest species were among the most
influential species, mainly through colonisation, while warm-dwelling
farmland species 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 with the main expectations due to
global change (thermophilisation), mainly due to local colonisation of
warm-dwelling species, although it did not show the pattern of thermal
homogenization suggested elsewhere. Our results add further evidence of
the interplay between climate warming and land-use change in the ongoing
adjustment of animal communities.