The detection of bird migration by high-power radar

Abstract

The new and more powerful R.A.F. 10 cm radar sets frequently detect ‘angels’ to ranges exceeeding 60 miles from the station. The seasons and times of day of their occurrence, their speed in relation to the wind, their directions of movement, and the influence of the weather, all fit the view that such echoes come from migrating birds, especially passerine birds. At a Norfolk station, the heaviest activity occurred eastwards in March and April, with a peak around 22.00 h G.M.T., and west-south-west in October and November, with peaks around 22.00 h and 10.00 h G.M.T.