DOI: 10.5061/dryad.qnk98sffh
title: Data from: Wintering bird communities are tracking climate change faster than breeding communities

description: 1. Global climate change is driving species’ distributions towards the
 poles and mountain tops during both non-breeding and breeding seasons,
 leading to changes in the composition of natural communities. However, the
 degree of season differences in climate-driven community shifts has not
 been thoroughly investigated at large spatial scales. 2. We compared the
 rates of change in the community composition during both winter
 (non-breeding season) and summer (breeding) and their relation to
 temperature changes. 3. Based on continental-scale data from Europe and
 North America, we examined changes in bird community composition using the
 community temperature index (CTI) approach and compared the changes with
 observed regional temperature changes during 1980–2016. 4. CTI increased
 faster in winter than in summer. This seasonal discrepancy is probably
 because individuals are less site-faithful in winter, and can more readily
 shift their wintering sites in response to weather in comparison to the
 breeding season. Regional long-term changes in community composition were
 positively associated with regional temperature changes during both
 seasons, but the pattern was only significant during summer due to high
 annual variability in winter communities. Annual changes in community
 composition were positively associated with the annual temperature changes
 during both seasons. 5. Our results were broadly consistent across
 continents, suggesting some climate-driven restructuring in both European
 and North American avian communities. Because community composition has
 changed much faster during the winter than during the breeding season, it
 is important to increase our knowledge about climate-driven impacts during
 the less-studied non-breeding season.
description: The data has been collected using breeding and winter bird
 surveys and the detailed methodologies are given in the Supplements of the
 article. The community temperatures are calculated using methodology of
 Devictor et al. 2008.  Devictor, V., Julliard, R., Couvet, D. & Jiguet, F. (2008) Birds are tracking climate warming, but not fast enough. <i>Proceedings of the Royal Society B</i>, <b>275</b>, 2743–2748. https://doi.org/10.1098/rspb.2008.0878
description: The dataset includes two files, one for annual changes and one
 for long term changes in community temperature index of birds and related
 temperature values. The annual data includes annual
 (fyear) estimates (fit), the standard error of the change (se) and 95%
 confidence intervals (lower, upper) of community temperature indices (CTI)
 in 57 regions (Country) in North America (Continent) and Europe for
 breeding and winter seasons (Season). Annual change in CTI (dCTI) and
 temperature (dTemp) as well as CTI of previous year of regions are also
 given. The long-term data includes long-term change
 (annual slope, dCTI) and the standard error of the change (CTI_se) in
 community temperature index (CTI) in 57 regions (Region) in North America
 (Continent) and Europe for breeding and winter seasons (Season).  Raw mean
 CTI value (mCTI_raw) and centred CTI (mCTI), coordinates (Lat, Lon),
 long-term change in temperature (Temp) and its standard error (TempSE),
 predicted CTI changes (CTITempPred), mean raw temperature (mTemp_raw) and
 centred mean temperature (mTempSt) of regions are also given.
 In addition two R scripts to analyses the data
 (CTI_Annual_Analyses_20200817.R and CTI_Longterm_Analyses_20201130.R) are
 included.