Advances in spring but variable autumnal trends in timing of inland wader migration

Advancement of spring migration in response to recent global climate change is well documented for a variety of bird species, but the pattern for autumn migration is rather equivocal. During a 42-year period (1964-2005) the changes in timing of spring and autumn migration of eight wader species were Studied at Multiple inland sites in Central Europe (Czech Republic and Slovakia) using ringing data. While a clear pattern was found for the advancement of the spring passage, there were variable trends in the timing of the autumn passage. Three species significantly advanced (Wood Sandpiper, Common Sandpiper and Dunlin), three species delayed (Ruff, Snipe and Little Ringed Plover), and two species did not change the timing of the autumn passage (Little Stint and Green Sandpiper). Earlier studies had predicted that long-distance migrants wintering South of the Sahara Would advance the timing of autumn migration, while short-distance migrants would postpone it. However, our findings do not fully conform to these predictions. Across species, the timing of both the spring and autumn passages was negatively associated with the winter North Atlantic Oscillation (NAO) index, suggesting that even in long-distance migrants the timing of migration might be under direct environmental control. In conclusion, phenological responses of birds to recent changes in climate are quite coherent for the early phenological phases; however, the responses to later phases are not so straightforward, and the present study contributes to this diverse pattern.