Data from: Climatic predictors of long-distance migratory birds’ breeding productivity across Europe

Ongoing climate changes represent a major determinant of demographic
processes in many organisms worldwide. Birds, and especially long-distance
migrants, are particularly sensitive to such changes. To better understand
these impacts on long-distance migrants’ breeding productivity, we tested
three hypotheses focused on (i) the shape of the relationships with
different climate variables, including previously rarely tested quadratic
responses, and on regional differences in these relationships predicted by
(ii) mean climatic conditions and (iii) by the rate of climate change in
respective regions ranging from Spain to Finland. We calculated breeding
productivity from constant effort ringing sites from 11 European countries
covering 34 degrees of latitude, and extracted temperature- and
precipitation-related climate variables from E-OBS and NASA MODIS
datasets. To test our hypotheses, we fitted GLMM and Bayesian
meta-analytic models. We revealed hump-shaped responses of productivity to
temperature, growing degree-days, green-up onset date, and precipitation
anomaly, and negative responses to intense and prolonged rains across the
regions. The effects of March temperature and April growing degree-days
were more negative in cold than in warm regions, except that one with the
highest accumulated heat, whereas increasing June precipitation anomalies
were associated with higher productivity in both dry and wet regions. The
rate of climate warming was unrelated to productivity responses to
climate. The influence of climate on bird productivity proved to be
frequently non-linear, as expected by ecological theory. To explain the
differences between regions, the rate of climate change is less important
than regional interannual variability in climate (which is predicted to
increase), but this may change with the progression of climate change in
the future. Productivity declines in long-distance migratory songbirds are
particularly expected if out-of-norm water excess increases in frequency
or strength.