in 2000, 3 new pairs were looking for territory and probably established (each one undertaking no breeding attempt):
- pair 8
first identified in a territorial fight with pair 2 in their second nesting place in 1999;
- pair 9
also identified in 1999 calling from the area, where is now their territory;
- pair 10
first identified and present in 1998 (!), when it appeared in a group of 4 youngsters, landed in a pond and unison called!
Figure 7, Figure 8 and Figure 9 (PDF) display a qualitative overview over the distribution of the crane territories and the changes observed by sonography.
ith these tools and experiences in hand we replayed and digitalized analogous recordings on magnetic tape, taken by E. Henne over many years in Brandenburg, in an area of comparable size like the one in Hamburg with 7 - 9 territories, several of which had been very close together, and analysed them with the same method. Including 1998, the files are comprising 37 "crane-pair years".
The analysis (summarised in table 1) showed a remarkable stability of the crane pairs in their territories over years, although the places were rather close to each other. In all 6 territories, for 2 and more (up to 6) subsequent years it could be documented that the same pairs were present: 34 times, territories were occupied the next year, too, 29 times by the previous pair.