The detection of flying targets in the night sky has provided interest for bird migration research over many years with methods largely dependent on moon watching or the use of radar and infrared camera. These methods lack the versatility of the system described in this paper which detects and automatically records aerial targets in the night sky of a size greater than 5 cm and at a distance of 100 to 1000 metres from the observer. The principle design features are first, an optical device for

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... eceiving images of targets on two high-sensitivity CCD matrices when illuminated by white light from searchlight beams and secondly, instantaneous parallactic electronic computation enabling the distance from device to target to be accurately measured, and sequential images of each target to be recorded to computer. The device has been tested on targets during the main seasonal nocturnal migration of birds and provides accurate image details of important target flight parameters including : altitude, linear size (wing span and body length), direction of flight (ground track), orientation of the body axis -heading, ground speed, wing-beat frequency, number of wing-beats in each series of beats, duration of the pause between each series of wing-beats, and type of flight trajectory. There are also the potential practical applications for aviation bird-strike at night as well as the remote monitoring of insects, bats and other targets of natural and artificial origin. K E Y W O R D S 1. Electronic-optical device. 2. Nocturnal bird migration.