Autumn migration 2018
Newsletter 27/10/2018
The autumn migration of our Northern Bald Ibises started quite regularly in early August. The birds from Burghausen and Kuchl left their breeding areas and gathered at the alpine foothills.
Based on previous data, we expected them to cross the Alps by mid-September. However, patience was required this year. In early October, the sub-adult birds that spent the summer south of the Alps began to fly back to the wintering area.
Finally, on October 22, some of the other birds on the northern edge of the Alps started to continue their journey towards south. The highlight so far was a group of two adult, experienced birds, followed by six juvenile ones: On October 22, those eight birds left the Inn Valley in Tyrol and flew about 280 km to Lake Garda in Italy. On October 23, they flew the remaining 400 (!!) km to the wintering area in one go. Never before have we registered such a large daily flight distance and, to our knowledge, such large flight distances have so far been generally unknown in Northern Bald Ibises.
One of the juveniles of said group was transferred from Zoo Zurich at the end of July in order to optimize the genetic variation in our population. This was the first such supplementation; the bird by the name of Silvretta showed that this method is working.
A second bird from Zoo Zurich by the name of Säntis had lost contact with its conspecifics in September; it then had flown to Switzerland and since then had been staying at Lake Zurich. From there, Säntis then departed almost simultaneously with the group of eight birds in Tyrol and flew around 220 km directly over the Western Alps to Zermatt. On October 24, Säntis then flew past the Matterhorn into Valle d'Aosta and on to Italy, arriving near Turin. The highest GPS position of the bird was registered at approximately 2,800 meters above sea level. This, according to our knowledge, is the highest known flying position of a Northern Bald Ibis so far.
It is also interesting to compare the flight routes of these two Zurich birds. Silvretta followed the experienced individuals on a perfect route towards south directly to the wintering area in Tuscany. Säntis, however, was on its own and consistently followed a route towards south west. Such data impressively show the interplay between genetic and socially learned information: young Northern Bald Ibises are genetically adapted to migratory behaviour. During autumn of the first year of live, however, they need the help of experienced conspecifics to reach a suitable wintering area.
Säntis has managed the hardest part of the migration on its own. We continue to monitor his GPS positions and hope that he stays in Italy. Maybe he will meet migrating conspecifics there. Otherwise, we will try to catch Säntis to bring him to the wintering area in Tuscany.
Picture: The map shows the flight paths of the two Zurich birds. While Silvretta followed its conspecifics directly into the wintering area, Säntis was on its own and followed a genetic direction vector in consistent south-west direction.
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