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ABSTRACT
In spring 1992, steppe buzzard migration was studied by tracking radar in the Arava Valley near Hazeva (150 m below sea level) and in the Negev Highlands near Sede Boqer (470 m above sea level). Entire gliding and soaring phases were recorded. The flight altitude of the steppe buzzards depended on the time of day. Migration was slightly higher above ground and lasted longer towards sunset in the Arava than in the Negev. The maximum altitudes, about 2000 m above ground in the Arava and about 1000 m in the Negev, were reached in the early afternoon. The relatively low average climbing rates in thermals of 2 m/s can be explained by the fact that the whole diurnal circle is included in this average and that the observation sites were not situated at the edge of large rocky slopes where large thermal updrafts occur, but rather on flat surfaces. Strong thermals were used longer for soaring than weak ones. The climbing rate in thermals was a decisive trait when explaining the flight behavior of migrating steppe buzzards; the flight altitude, the gliding airspeed, and consequently the cross-country speed increased with increasing climbing rates. The average cross-country speed was 9.8 m/s and was considerably enhanced by tailwinds.