Biržai: Flora and fauna
Covering 1476 square kilometers, 26 % of Biržai district consists of forests. Biržai was established at the confluence of the Apaščia and Agluona rivers, near the man-made Lake Širvena. Almost all of the Biržai district area lies in the basin of the district’s largest river, the Nemunelis, which is 191 km long. There are 17 lakes in Biržai district, most of them quite small, and 28 rivers and streams longer than 5 km.
One of the rivers that flows into Širvėna lake is the Apaščia river. Its lenght is 88 km. From Širvėna lake the Apaščia flows its waters into another our district river the Nemunėlis. It is the border between Lithuania and Latvia. Further Nemunelis merges with the river Mūša and becomes the Lielupe river. Going through the Lielupe we can reach the Baltic sea.
Another river flowing into Širvėna lake is the Agluona. Its lenght is 21 km.
Lake Širvena was created in 1575 after damning the rivers Apaščia and Agluona at their confluence. It is the oldest artificial body of water in Lithuania. The lake was built to protect the Radvila castle in Biržai.
Now the city of Biržai, which was built around the castle, is located on the southern shore of Širvėna lake. The suburb of Astravas is built on the northern and the suburb of Rinkuškiai on the western shore. 525 m long wooden bridge across the lake was built in 1987. It is the longest foot bridge in Lithuania.
Some kinds of fish found in Širvena lake.
The main water plants are water lilies, pondweeds, reeds, bulrushes, cat‘s-tails.
3 kinds of birds, which were registered in the Lithuanian Red Book, are found in the reeds of Širvena lake. They are bitterns, black terns and great white herons. Bitterns and black terns breed in the lake, but great white herons just feed there. During the autumn migration flocks of ducks and geese settle in the lake. Some pairs of swans also breed in the lake.
The lake is homelike for beavers, minks and otters. The lake and its shores are great habitation for amphibias, i. e. tritons, frogs and toads.
Some kinds of fish are found in Širvena lake. Roach is the most dominant fish. Also there are bass, crucians, pike, etc.
The main water plants are water lilies, pondweeds, reeds, bulrushes, cat‘s-tails.
