Recently the study of plant and animal phenological observations has contributed much to understand the sensitivity of biosphere to the variability of its atmospheric environment. This study is based on time series of 3 bird phenological phases (‘first barn swallow’, ‘first cuckoo call’ and ‘all swallows have left’) from the archive of the Central Institute for Meteorology and Geodynamics in Vienna, which have been collected at 65 Austrian stations from 1951 – 1999. In contrast to many European countries the arrival times of barn swallow and the cuckoo have predominantly been moving to later dates in Austria. A preliminary analysis points towards dryer conditions in the sub - saharan winter quarters as possible cause for a later departure from the African winter quarters to Europe. About
a third of the year to year variability of both spring bird phases can be explained by temperature and wind conditions on the migration route and local temperature
