Disentangling the relative roles of climate and land cover change in driving the long-term population trends of European migratory birds

Authors:  Christine Howard, Philip A. Stephens, James W. Pearce-Higgins, Richard D. Gregory, Stuart H.M. Butchart, Stephen G. Willis

Year: 2022

Publication: Diversity and Distributions

Publication Link: https://onlinelibrary.wiley.com/doi/full/10.1111/ddi.13144

Keywords: Africa, avian migration, breeding, climate, Europe, habitat, non-breeding, population trends


Aim: Global declines in the populations of migratory species have been attributed
largely to climate change and anthropogenic habitat change. However, the relative
contribution of these factors on species’ breeding and non-breeding ranges is unclear.
Here, we present the first large-scale assessment of the relative importance of
climatic conditions and land cover on both the breeding and non-breeding grounds in
driving the long-term population trends of migratory species.

Location: Europe and Africa.

Methods: We use data on the long-term population trends of 61 short- and 39 longdistance
migratory species of European breeding birds. We analyse these population
trends in relation to changes in climate and land cover across species’ breeding and
non-breeding ranges over a 36-year period, along with species’ migratory behaviour.

Results: The population trends of European migratory birds appear to be more
closely related to changes in climate than changes in land cover on their breeding
grounds, but the converse is true on their non-breeding grounds. While improvements
in climate suitability across the breeding ranges of short-distance migrants led
to increasing population trends, the same was not true for long-distance migrants.
The combined effects of changes in climate and land cover account for approximately
40% of the variation in migratory species’ population trends, suggesting that factors
other than climate and land cover as we have measured them, such as habitat quality,
also affect the population trends of migrant birds.

Main Conclusions: Over recent decades, population trends of most migrant species
are most strongly related to climatic conditions on the breeding grounds but land
cover change on the non-breeding grounds. This suggests that management to stem
the declines of migrant birds requires an integrated approach that considers all processes
affecting migrant birds across their dynamic distributions throughout the year.

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