Development and Application of X-band Radar System for Automatic Detection and Registration of Migrating Birds

Motivated by the large request for baseline studies of migrating birds in connection with planned offshore infrastructure projects in the Danish parts of the North and Baltic Seas an existing X-band weather radar system (LAWR) has been adapted to tracking migrating birds. The use of radars in connection with ornithological field studies is not unknown, but the system developed here facilitates a new range of options which has been developed in cooperation with the users – the ornithologists and biologists.

Two systems exist: A system with a single horizontally rotating X-band radar providing estimates of the migration paths and a dual antenna system with two X-band radars, one rotating horizontally and one vertically, facilitating tracking of the birds' flight path as well as the flying altitude. The systems are operated with an effective range of 10 km and an image update frequency of one minute. The data processing is based on the raw reflectivity values observed by the radar and the variance estimate of each sample bin. The developed system provides estimates of the flight tracks – both their length and their geographical locations. By combining the radar with meteorological data such as wind speed it becomes possible to estimate the true flight velocity in the air which is an important parameter in the automatic species classification algorithm developed during this project.

The work presented here will focus on the results and experiences from the first 10 deployments – 4 single antenna systems and 6 dual-antenna systems. The radar estimates will be compared with traditional ground-based visual observations. The discussion will focus on performance of the system along with an analysis of the uncertainties affecting the estimates.