Successful start of the breeding with some surprises
Newsletter 29/04/2021
The season is off to a wonderful start this year. Many birds have already returned to the breeding grounds and more are still on the way.
In the breeding area of Burghausen in Bavaria there are already 20 eggs in 5 nests. The birds are breeding in the already established way in the breeding niches on the defensive wall of the castle in Burghausen.
In Kuchl near Salzburg there are also 5 nests with 17 eggs so far. There, the behaviour pattern of the previous year continues, with all birds breeding in natural niches in the rock face on the mount Georgenberg. The same rock face is also inhabited by kestrels (Falco tinnunculus). Last year we repeatedly observed attacks of the kestrels on the ibises and the ibises only stayed in the lower half of the wall, while the kestrels dominated the upper part. This year, however, there has been a striking change. There are at least six breeding pairs of kestrels in the wall, but there is hardly any interaction with the ibises anymore and there is also spatial mixing. The two species seem to have got on well together.
In Überlingen, breeding is somewhat delayed. The birds were initially slowed down by the bad weather. In the meantime, however, 6 birds are sitting in the breeding aviary near Überlingen and there are already two breeding pairs. Another 16 birds are on their way to Überlingen, so more breeding pairs will surely form soon.
Another breeding colony was established in 2019 at the southern edge of the Alps in Rosegg in Carinthia. Two birds have already arrived there this spring. Two more birds are on their way, but they are currently staying in Slovenia near Zagreb. There will be no breeding this year. The existing breeding niches are occupied by ibises from the resident sedentary colony. Next year, however, breeding structures will be built in Rosegg for the migrating birds too.
And then there is a very special curiosity. Two adult females flew to Rome from the winter area in spring. They laid three eggs on a window ledge of a building in the south-western part of the city. Concerned people then placed a cardboard box on the ledge and that is where the two ibises are now incubating the eggs. We assume, however, that the eggs are not fertilised and therefore no chicks will hatch.
The two birds in Rome belong to that small part of the Northern Bald Ibises that do not return to their breeding area even as sexually mature birds. They either show no migratory behaviour, fail to cross the Alps or migrate in divergent directions. We assume that this is a natural variation in a migratory population. So far, however, these birds have not attempted to breed. So this year we observe a new behavioural pattern and we also have, quite unexpectedly, the first breeding attempt in Italy as part of the reintroduction project.
Photo: One of the two females sitting on the three eggs on a window sill in Rome.
