I would like to thank my son Bengt and Inga Roedenbek for helping me to make the first recordings in 1998 in Hamburg. Volker Guenther accompanied me in Mecklenburg and showed me the crane territories there. Beate Blahy and Eberhard Henne did the same in the much bigger area in Brandenburg, and I am still impressed how well they know the area and all the more than 200 crane territories. Special thanks go to Eberhard who gave me his early recordings of the late 80s and early 90s which had never been analysed before.
I thank George Archibald for his consults and his generous help in providing me the possibility to record at the ICF in Baraboo and for introducing me to the Whooper Crane Recovery Team, to the Japanese and Korean crane experts who helped me in my field work there (Yulia Momose, Kimiya Koga, Mr. Matsuo, Mr. Pae. Many thanks go also to the Whooping Crane Recovery Team and especially George Gee who arranged the possibility for my recording in Patuxent. Tom Stehn (coordinator of the Whooping Crane Recovery Team and chief biologist in ANWR) helped me to get to know the territories of the wintering Whooping cranes there, Brian Johns (the Canadian Whooping Crane project leader) learnt recording from me and was trained by me, which enabled him to make a valuable number of recordings in the breeding territories for my analyses.