Crane Grus Grus Migration Over Sea and Land

Summary The detailed process of Crane Grus grus migration over sea and land, respectively, was studied from films of a radar station in Skåne, southernmost Sweden, during the spring migratory periods in 1972 and 1973. The true air speed for travelling over the sea was 67 km h‐1, whereas over land the Cranes made use of thermal air to soar and gain height and the true air speed was 44 km h‐1. Soaring lasted on the average 6.3 min and the distance travelled between the soaring interludes was 13.3 km. True air speed during the flights between thermals was about 70 km h‐1. The Cranes compensated completely for wind drift over land, but only incomplete compensation took place over the sea. The angle between the Cranes' heading and track directions over the sea was composed of 68% compensation and 32% drift.