Missed the right moment? Überlingen Northern Bald Ibises still sitting in their breeding area
Newsletter 20/11/2021
In the three breeding areas of Burghausen, Kuchl and Rosegg, autumn migration has proceeded well and is largely complete. Moreover, for the first time a large group of 22 birds migrated together from Salzburg to Tuscany. The situation is different, however, for the 31 birds of the Überlingen colony, which are still fully settled in their breeding area. There was a recent departure of a total of 6 ibises. However, the flight stopped near Chur in Switzerland and the birds finally returned to Überlingen.
In 2014 we were confronted for the first time with a severely delayed or missed departure of the ibises from the Salzburg colony. The birds were still in the Salzburg countryside at the beginning of December. At that time, we assumed that they would still depart, as this had also been the case in the past. But a sudden onset of winter threatened the whole group and despite immediate capture, some birds froze to death.
In the following years, it has become apparent that the timing of the birds in autumn is becoming more and more variable. Sometimes the first southward departures take place as early as the beginning of October, sometimes not until November. Apparently, the departure is strongly determined by external conditions.
Again and again, the fascinating phenomenon of the synchronisation of groups at different locations can be observed during the departure. This was also the case this year, with the exception of the Überlingen birds. While the bald ibises of other colonies migrated synchronously when there were good flying conditions, they stayed on site.
It may have played a role that the birds in Überlingen were kept on the ground by frequent ground fog. However, as the timing of the bald ibises in autumn is generally becoming more and more variable, we assume much more basal causes that are directly related to climate change. The fact that only the Überlingen colony was affected this year may have something to do with the group composition. This group consists entirely of young birds with little migratory experience.
All this is mostly speculation, based on many years of experience. So far we have lacked the necessary data to investigate these complex relationships scientifically. This is a goal for the next few years. But at least our experience allows us to manage these situations efficiently. According to the weather forecasts, the birds are not yet acutely threatened by a winter onset and we can still wait and see what happens. Perhaps favourable conditions for migration will still come in the near future. But by the beginning of December at the latest, we will have to catch the birds and release them along the migration route in South Tyrol. There they are out of the danger zone and can migrate further into the winter area by themselves. And according to our experience, they will do so. We also know that these birds are very likely to migrate quite regularly the next year.
The current situation of the Überlingen bald ibises is of course neither expected nor pleasing. But it does not endanger the further existence of this colony. And it is precisely such anomalies that often offer the chance to gain a deeper understanding of complex correlations. And sound knowledge about the influence of climate change on the complex phenomenon of migration is not only important for the reintroduction of the Northern Bald Ibis. More and more migratory bird species are showing similar anomalies (in the German version here) and it can be assumed that these phenomena will increase in the future.
Photo: The Überlingen ibis-group in flight. We really hope to see them like this soon. (Photo: Waldrappteam)
