GASTEREN H VAN (2008) Do migratory birds beat the speed record of the Peregrine's stoop dive?. LIMOSA 81 (2): 68-70.

Migratory birds are able to select the optimal altitude layer, i.e. the altitude with most profitable wind, for migration up to ca. 4 km altitude in NW-Europe. Wind speeds exceeding the birds'own airspeed, that thus double the groundspeed, normally break off their migratory flight. In the morning of 26 February 2008 the longrange surveillance radar of the Belgian Air Force measured large bird echoes flying at an altitude of 2-3 km in NE direction. Due to high wind speeds in the migratory direction (up to 27 m/s) the migratory birds reached groundspeeds of up to 55 m/s (mean 41 m/s). The corresponding airspeed of 16 m/s most probably fits ducks or larger waders. In literature only the use of low-level jets reaches the same order of horizontal groundspeeds by migrating birds. Only the Peregrine Falcon's stoop dive still exceeds these horizontal speeds of 200 km per hour.

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