Ørnsø
At Ørnsø, birdlife changes with the seasons, from swarming starlings to summer warblers and the quiet passage of the osprey. Beneath the surface lives an unusually rich fish population, in a lake where the rhythm of nature and the state of the water continue to evolve.
Bird life
Autumn
As autumn approaches, both swallows and starlings gather in the lake’s reed forests to spend the night. Before the starlings find peace for the night, some years you can witness impressive flocks that hover over the lake, creating the breathtaking phenomenon known as the “black sun”. From late August until October you can also spot the osprey, soaring majestically on its way south during the autumn migration towards Africa.
Winter
During the winter months, the lake is visited by many ducks from all over the Nordic region. Great martin, wigeon, troll and swans can be seen on the lake. If the lake freezes over, the birds will gather in the wake where Funder Å flows out at the western end of the lake.
Spring
In April and May, the osprey is often seen soaring majestically over the lake on its way from Africa to breeding grounds in Sweden and Norway. The sharp whistle of the kingfisher sounds as it flies low over the water, and from mid-May, lucky visitors can catch a glimpse of the night owl chicks sitting in the old beech trees on the south side of the lake. On the water, the great crested grebe can also be seen performing its fascinating mating dance, shaking its head vigorously.
Summer
In the meadow at the western end of the lake, in early summer, you can hear the little warblers whistling beautifully at dusk. The nightingale's melodious song can be heard by the lucky ones, while the cuckoo is busy finding suitable bird nests in the reeds for its eggs. On the lake, both great grebes and coots can be seen in a zealous battle for invisible territories that must not be crossed. The cormorant dives for fish in the lake and often spends the night in trees along the shores of the lake.
The Water
The water in Ørnsø
Ørnsø gets most of its water from Funder Å, which, like Arnakkekilden and several other springs in the area, is rich in iron. From Ørnsø, the water flows through Lyså and out into Silkeborg Langsø.
An unusually rich fish life
Although the water is often murky, Ørnsø contains one of Denmark's most species-rich fish populations. A total of 15 species were recorded in a survey in 1998, including: bream, smelt, roach, pike-perch, pike-perch and roach. The roach is the dominant species, which typically thrives in nutrient-rich lakes.
