Quantifying Bird Migration by a High-Resolution Weather Radar

We propose a bird detection and count algorithm designed to work with radar maps of plan-position-indicator type. The spatial arrangement of birds is modeled according to the Poisson distribution. It is possible to handle a nonuniform target distribution both on the vertical and horizontal planes. The method is applied to measurements carried out by an S-band Doppler weather radar located on the south side of the Alps. Quantitative estimates are given for the distribution of bird volume density with height, the cumulative density (integrated over height), and, finally, the daily migration traffic rate of nocturnal migrants over an area of about 2000 km².