Acknowledgements

I would like to thank my son Bengt and Inga Roedenbek for helping me to make the first recordings in 1998. Thanks go also to Frank Golchert for helping me to assemble the hardware, and to Holger Hoffmann for his contributions during the development of the mathematica script.

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, Prof. Masatomi, Kimiya Koga, Mr. Matsuo, Mr. Pae). My thanks go also to the Whooping Crane Recovery Team and especially George Gee who arranged the possibility for my recording in Patuxent, Tom Stehn who supported my recording in Aransas, and Brian Johns, who recorded in WBNP. Thanks also go to Operation Migration (Bill Lishman, Joe Duff) for their support for applying the vocal communication technique during the UL-led migration.