North Atlantic Oscillation timing of long- and short-distance migration

1. The timing of migration is associated with survival and reproductive risks of migrating species. Hence, variation in factors influencing this timing, such as climate, may have significant life history consequences for migrating species. 2. Using an autoregressive phenological model, we analysed and contrasted the effects of climate (the North Atlantic Oscillation, NAO) and temporal dependence on the long-term (1928-77) dynamics of springtime arrival in three long-distance (83 populations) and three short-distance (52 populations) migratory bird species breeding throughout Norway. 3. Following high NAO winters both long- and short-distance migrants arrived earlier than after low NAO winters. For long- distance migrants, the effect of high NAO winters was probably indirect through improved forage conditions in winter quarters, whereas the effect on short-distance migrants may be related both to improved forage and weather conditions during their northward spring migration. The NAO explained on average 13% (0-46%) and 18% (0-43%) of the interannual variation in arrival dates of long- and short-distance migrants, respectively. 4. For both migrant types, long-term variability in springtime arrival increased with increasing strength of the influence of the NAO on timing of migration. In contrast, the strength of temporal dependence was unrelated to variability in long- term springtime arrival.