Migratory diversity predicts population declines in birds

James Gilroy, Jennifer Gill, Stuart Butchart, Victoria Jones, Aldina Franco

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Declines in migratory species are a pressing concern worldwide, but the mechanisms underpinning these declines are not fully understood. We hypothesised that species with greater within-population variability in migratory movements and destinations, here termed ‘migratory diversity’, might be more resilient to environmental change. To test this, we related map-based metrics of migratory diversity to recent population trends for 340 European breeding birds. Species that occupy larger non-breeding ranges relative to breeding, a characteristic we term ‘migratory dispersion’, were less likely to be declining than those with more restricted non-breeding ranges. Species with partial migration strategies (i.e. overlapping breeding and non-breeding ranges) were also less likely to be declining than full migrants or full residents, an effect that was independent of migration distance. Recent rates of advancement in Europe-wide spring arrival date were greater for partial migrants than full migrants, suggesting that migratory diversity may also help facilitate species responses to climate change.
Original languageEnglish
Pages (from-to)308–317
Number of pages10
JournalEcology Letters
Issue number3
Early online date25 Jan 2016
Publication statusPublished - Mar 2016

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