... by performing orientation cage experiments and making simultaneous observations of free-flying birds using a tracking radar. The flight directions of free-flying birds were mainly towards southwest and did not differ between overcast and clear sky conditions. The caged birds, however, tended towards southwest...

...Bruno Bruderer; Dieter Peter; Thomas Steuri ABSTRACT Radar studies on bird migration assume that the transmitted electromagnetic pulses do not alter the behaviour of the birds, in spite of some worrying reports of observed disturbance. This paper shows that, in the case of the X-band radar...

... , P. B. and Sattelle , D. B. ( 1979 ). A radar-Doppler autocorrelation analysis of insect activity . Physiol. Entomol . 4 , 103 – 109 . Buruma , O. J. S. , Kemp , B. , Roos , R. A. C. , Franzen , J. M. and Van Der Velde , E. A. ( 1982 ). Quantification...