Rapaid Advance Of Spring Arrival Dates in Long

Several bird species have advanced the timing of their spring migration in response to recent climate change. European short-distance migrants, wintering in temperate areas, have been assumed to be more affected by change in the European decimate than long-distance mi-grants wintering in the tropics. However, we show that long-distance migrants have advanced their spring arrival in Scandinavia more than short-distance migrants. By analyzing a long-term data set from southern Italy, we show that long distance migrants also pass through the Mediterranean region earlier. We argue that this may reflect a discriminate evolutionary change in the timing of spring migration. Many biological processes are affected by climate, and in temperate areas, the increasing spring temperature over the past so to 30 years has caused an advancement of phonological events in plants and invertebrates (1, 2). The earlier onset of spring has consequences for the timing of breeding in birds, which has evolved to match peak food availability (3, 4). We may therefore expect the timing of breeding to track any temporal shift in food availability caused by a trend in spring temperature (5). Most pas serine birds (which constitute more than half of all 

bird species) breeding in temperate areas of the Northern Hemisphere are seasonal migrants, and the timing of migration ultimately con-strains when breeding can start (6, 7). Short-distance migrants, spending the winter dose to the breeding grounds, may be able to adjust the timing of migration in response to local climate change, which will be correlated to the conditions on the breeding grounds. In tropical-wintering long-distance migrants, the timing of migration is under endogenous control (8, 9), and the cues needed to trigger the onset of migration are unlikely to be linked to the climate on their breeding grounds. Therefore, it has been assumed that short-distance migrants are more likely than long-distance migrants to vary migration timing in response to climate change (10). Here we show that such an assumption is not empirically justified. We estimated trends in arrival time for the early, middle, and late phases of migration (that is, the species- and site-specific loath, loath, and Both percentiles of the spring arrival distribution) in short- and long-distance pas serine migrants, based on long-term banding and observational data (from 1980 to 2004) from four bird observatories in Scandinavia and a site in southern Italy (RR). We also investigated whether year-to-year variation in arrival time can be explained by short-term climate variability as measured by the North Atlantic Oscillation (NANO) (re). As explanatory variables, we used the calendar year (TIME) and the deviations from linear regression of the winter NANO index on year (MAO) [the trend in NANO was weakly negative over this time period (n)]. Spring migration might advance for two distinct reasons. First, there can be a micro evolutionary (genetic) response to the selection pressures for earlier breeding. Second, the migrants can show a photogenically plastic response to trends in weather or climatic patterns on the wintering ground and/or along the migration route, whereby if spring arrives early on the wintering grounds, spring migration will also start early. Thus, a response to TIME may reflect either micro evolutionary change or phenotype plasticity, whereas a response to DNA indicates exclusively phenotype plasticity in the migratory behavior. Long-distance migrants have advanced their arrival in northern Europe in all phases of migration (see tables Si to Se online and Fig. a). The advancement in long-distance migrants is strongest in the early phase of migration, and there is limited variation between species. Furthermore, the analysis of the data set from Italy (from the island of Capri) showed that long-distance migrants wintering south of the Sahara are actually arriving in southern Europe progressively earlier. In fact, all of the nine species analyzed show a trend for earlier spring arrival at Capri in most phases of migration (see table 4 online and Fig. a). The long term trend on Capri is at least as strong as that observed in Scandinavia. In short-distance migrants,