The regional and seasonal status of bird migration determined by weather radar

Abstract

The Wind Profiler, a meteorological radar for wind direction and speed, detects the 'bird echoes' that are returned mainly from migrating birds. We reported regional and seasonal status of bird migration by analyzing the echoes collected at 31 sites across Japan during the period from August 2003 to December 2007. The bird echoes were frequently recorded during April to June, and August to November, at all the sites. The peak seasons, however, were a earlier at southern sites in spring and later in autumn. The frequency of echoes increased 1-2 hours after sunset, and decreased after midnight. The time after sunset at which the echoes increased during autumn migration was frequently later than the time that they increased during spring migration, and the start time became earlier as the season progressed. Both spring and autumn migrations were frequently observed and recorded at sites along the Japan Sea, but sites along the Pacific coast frequently only had recordable autumn migrations. Combine bird ringing data, the Wind Profiler may allow us to monitor many aspects of bird migration across Japan.