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Climate patterns and the stochastic dynamics of migratory birds


  • Niclas Jonzén,

  • Anders Hedenström,

  • Christian Hjort,

  • Åke Lindström,

  • Per Lundberg,

  • Arne Andersson

N. Jonzén, P. Lundberg, Dept of Theoretical Ecology, Ecology Building, Lund Univ., SE-223 62 Lund, Sweden ( – A. Hedenström, Å. Lindström, Dept of Animal Ecology, Ecology Building, Lund Univ., SE-223 62 Lund, Sweden. – C. Hjort, Dept of Geology, Lund Univ., Sölvegatan 13, SE-223 62 Lund, Sweden. – A. Andersson, Sofiavägen 5A, SE-222 41 Lund, Sweden.


We analyse time series data of 17 bird species trapped at Ottenby Bird Observatory, Sweden, during spring migration 1972–1999. The species have similar demography but respond differently to variation in the North Atlantic Oscillation (NAO) – a strong determinant of winter climate in the northern Hemisphere. Species wintering in northern Europe, compared to species having winter quarters in the Mediterranean area, tend to respond positively to variation in NAO. The variation within each group is high due to wide-ranging winter-distribution in many species, probably smoothing out the effect of spatial variation in NAO. Whereas mild winters (high NAO) is benign for many – but not all – birds wintering in northern Europe, the effect of drier-than-normal conditions in the Mediterranean area during high NAO index winters are uncertain. The work presented here goes beyond simple correlative studies and help identifying which species that are most affected by variation in winter climate. This is a first important step that calls for a more mechanistic approach when analysing possible changes to climate change.