Ismaning – bird paradise at the reservoir – district of Munich

Of course, Karin Haas knows the best spot for a view of the lake. She has been area manager for the reservoir in the State Association for Bird Protection (LBV) since 2010 and naturally knows from where swans, greylag geese, herons and ducks can be observed particularly well. This morning, the path leads from the road through the dense and shady alluvial forest, which is astonishingly green after the drought of the past few weeks and months. The dampness of the previous cool night is clearly still in the branches and thickets. Arriving at the top, the whole beauty of the body of water artificially created in 1929 to generate electricity on the Middle Isar Canal and its feathered guests can be seen. It is very quiet on this clear and sunny day. The water surface of the reservoir glitters and shines. Lots of waterfowl sit as if on a huge mirror, undisturbed by the noise of civilization – and do credit to the important bird paradise between Ismaning, Aschheim, Kirchheim, Pliening and Finsing, which is known throughout Europe.

A central dam divides the reservoir, which was artificially created in 1929, into two basins

The reservoir is about seven kilometers long and up to 1,300 meters wide. A central dam divides the body of water into a western and an eastern basin, in which an unimaginably large number of different bird species cavort. 50,000 to 60,000 animals are guests in the high season in July, now it should be 30,000 to 40,000. They come from all over Europe to moult and find ideal conditions at the reservoir to shed their feathers. According to Haas, the LBV estimates that all in all more than 100,000 waterfowl fly to Ismaning to moult. No wonder the bird sanctuary is particularly popular with ornithologists. Since 1929, more than 280 species (excluding zoo refugees and other exotic species) have been observed at the reservoir and the ponds and recorded in the archives of the Ornithological Society in Bavaria (OG). This has been ornithologically in charge of the area since 1929, carries out counts and documents sightings.

Keeps a close eye on the reservoir and the Teichgut: Karin Haas, area manager of the State Association for Bird Protection (LBV).

(Photo: Robert Haas)

According to Haas, the reservoir has become one of the most important refuges for moulting in recent years for red-crested pochard and gadwall ducks. In the months of July and August over the past ten years, at least 15,000 of these two duck species have dropped their flight feathers at the reservoir, reports Haas, before most of them set off for the Camargue in France. The graduate biologist is out and about at the lake and the Teichgut two to three times a week. During the summer months, counts are also scheduled every other weekend. Coots, great crested grebes, mute swans, herons, cormorants, for example, are located and counted.

For many of the feathered companions who come from the northern climes, the reservoir is, unlike in the past, not only their place of choice for moulting in summer; they stay, even when the days are getting shorter again and the temperatures are dropping. The number of overwintering guests has increased, Haas and the bird counters have determined. Climate change makes it possible.

And it is also quite noticeable in the opposite direction. For example, that nowadays yellow-legged gulls also fly to the large bird sanctuary to breed – and look out for food, i.e. smaller birds such as ducks, as Karin Haas reports. On this morning at the lake there is no one to be seen, not even a distant call that sounds like “kijo kijo kijo” can be heard. Luckily for the countless guests on the lake. Nevertheless, they feel a little disturbed and retreat further to the middle of the west basin when Karin Haas sets up her waterproof spotting scope at the top of the dam, with which the individual birds can be viewed up close, and lots of interesting facts about swans, ducks and Heron tells.

Bird Sanctuary: The Heron

The heron

(Photo: Claus Schunk)

Bird sanctuary: The coot

The coot

(Photo: Florian Peljak)

Bird sanctuary: The great crested grebe

The great crested grebe

(Photo: Felix Kästle/dpa)

Otherwise, however, the consequences of warming and drought in the reservoir can hardly be seen with the naked eye. On the one hand, this is because the lake is fed by water from the Isar. Because of its shallow depth, which according to Haas is only one to two meters in some places but around four meters in other places, the reservoir is quite warm anyway. According to Haas, there is no need to fear that the reservoir and the chain of ponds will dry out, as seepage or evaporation is known in technical jargon, because wastewater from the Isar and Munich flows into it. The water level usually varies by a mark of 80 centimeters anyway. There is also no danger that the lake could “overflow” after storms or heavy rain events. It is also impossible for flotsam and urban waste to be washed in, because this is intercepted with a rake at the southern inlet and fished out. What Haas and the bird counters are observing, however, is an increase in wintering guests at the lake.

In addition to the water regulation of the power plants on the Isar Canal and flood protection, the lake also serves the natural post-clarification of the Munich sewage water from Großlappen, which is still rich in nutrients. Swimming is forbidden, water sports too, but fishing is allowed. The Isar canal coming from the Isar branches for the first time directly after crossing under the A 99 motorway. A side canal is used to supply water to the ponds of the Birkenhof estate, whose carp farming was abandoned in 2000 for economic reasons. In this area, part of the sewage water is pumped by Uniper’s main pumping station between Unterföhring and Ismaning via an underground pressure pipeline into the fish ponds, before the water from the ponds is subsequently taken up again using a drainage canal. After another three kilometers, a canal supplies the reservoir. In order to permanently secure the bird sanctuary, the Bavarian Nature Conservation Fund finances the maintenance and care management.

The biologist has noticed a remarkable development in recent years: Because the sewage treatment plant in Großlappen removes phosphorus from the wastewater through the installation of modern technology, the phosphorus content of the reservoir today is 20 to 40 micrograms per liter. The water is no longer as rich in nutrients as it used to be – and above all much clearer. “We don’t have super-pure water here, but we don’t have dirty water either,” says Karin Haas, pointing to the lake below the steep bank. Since then, many aquatic plants that need light have grown in it, and fewer algae in the water. The major changes at Gut Großlappen took place in the 1990s. At that time there was a huge drop in bird numbers due to the drop in phosphate, because birds and carp competed for food. It only leveled off again over the years after the fish management in the Teichgut was given up. According to Haas, the number of birds is at least back to where it was before.

Bird sanctuary: Up to 30,000 gadwall ducks fly in and spend the summer at the reservoir north of Munich.

Up to 30,000 Gadwall ducks fly in and spend the summer at the reservoir north of Munich.

(Photo: Robert Haas)

The consequences for the birds were very different, according to Haas. Herbivorous species such as the red-crested pochard would have benefited, but the numbers of tufted ducks, which would prefer “a muddy ground” to nibble on insects, were declining. At the reservoir, however, nobody needs to worry about these populations: every summer, the voluntary waterfowl counters register a good 30,000 gadwalls and red-crested pochards in the bird paradise north of Munich, which fly in to shed their feathers and “rent” there for three to five weeks. because they are unable to fly during the moult and, if at all, only set off further south in the autumn. It remains to be seen whether the summer of 2022, which was much too hot and too dry, will be followed by a winter that is too warm again.

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