Various studies have explored the relationship between weather conditions on the periodic migration cycles of birds, however, there is limited knowledge on how weather conditions actually influence the bird migration at the individual fitness level. The information collected was insufficient to describe the birds' self-sustaining internal circadian rhythm and external signal to ensure adequate departure and arrival times of migration. This research elaborated on the factors contributing to the timing of migration using a long-term statistical dataset covering the longitudinal range in northwestern Europe. Environmental conditions, including: spring vegetation in Europe, local spring temperature in northern Europe, and the North Atlantic Oscillation Index. The phenological data were derived from spring data on migratory passerines from various remote islands: Heligoland in the North Sea, Christians and Jury in the Baltic Sea. A standard of 20 birds captured and observed per season at each ringing station for at least 12 years was incorporated into the research. Various species were excluded from the study due to the segregation migration route. These specifications narrowed the field to 12 species, six of these are short-distance migrants and the other six are long-distance migrants. The environmental data consists of the monthly normalized difference vegetation index (NDVI), a monthly average temperature of the local weather station and the winter index. NDVI demonstrates an approximation of ecological conditions across regions and years. By averaging the different weather stations and taking the average of each of the spring months, you can calculate the overall provincial temperatures for the months. This was necessarily due to... middle of paper... atmospheric conditions will dramatically affect migratory bird populations if only a small fraction of migratory birds manage to adapt to environmental changes. Evidence of global warming driven by phenological changes in species is rapidly mounting. Limited knowledge of the genetic, physiological and behavioral control mechanism of bird migration limits scientists' ability to predict the significant effects of environmental changes on migratory birds. The lack of understanding of phenological changes in individual species prevents scientists from developing a plan for the future protection of the migratory organism. Works Cited Anders P. Tøttrup, Kalle Rainio, Timothy Coppack, Esa Lehikoinen, Carsten Rahbek, and Kasper Thorup. 2010 “Local temperature optimizes the timing of spring migration in birds.” Integrative and comparative biology 50:293-304.