Abstract
Birds flying at high altitudes have occasionally been observed above mountain areas and the open sea. For the first time the regular occurrence of migrating birds flying within a low-level jet at heights of 5000 to almost 9000 m asl. have now been verified by radar above the Negev desert in southern Israel. Tracks of rather large birds with wing-beat frequencies of 5–6 Hz were measured to have horizontal flight speeds up to 50 m/s. Visual observations, seasonal occurrence, and wing-beat frequencies allowed to associate them with small species of the order Ciconiiformes (mainly Ardeidae) and possibly with members of the Laro-Limicolae group. These wading birds seem prone to continuing nocturnal migration into daytime under favorable conditions and to make use of high wind speeds at sometimes extreme altitudes.
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Received: 21 June 1999 / Accepted in revised form: 26 August 1999
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Liechti, F., Schaller, E. The Use of Low-Level Jets by Migrating Birds. Naturwissenschaften 86, 549–551 (1999). https://doi.org/10.1007/s001140050673
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DOI: https://doi.org/10.1007/s001140050673