Tracking radar measurements of winds at the flight levels of bird migration during several migratory seasons in central Europe, southern Israel and the western Mediterranean are analysed with regard to optimal migratory behaviour in relation to wind. Bird Abstract Tracking radar measurements of winds at the flight levels of bird migration during several migratory seasons in central Europe, southern Israel and the western Mediterranean are analysed with regard to optimal migratory behaviour in relation to wind. Opposing winds prevail in central Europe, while at the western and eastern edge of the Mediterranean head- and tailwinds occur in similar frequencies.
Winds are highly variable in time and altitude.
Therefore, taking into account the wind situation carefully, a bird can almost double its flight speed and save about half of the energy required for its migratory journey through central Europe and the Mediterranean. The time needed for refuelling decreases accordingly or the safety margins provided by fat reserves can be increased. For birds flying long distances in one step, the selection of favourable winds should be more important than adjusting departure to local fat accumulation rates.