The lake Bogensee is located near Buch, just north of Berlin, on the border of the Pankow district. The lakes near Bogensee and the stream Lietzengraben form a restricted nature area (Naturschutzgebiet), that constitutes a safe place for birds and small animals to inhabit.
You can reach the area by taking the S2 S-Bahn line and getting off at the Berlin-Buch station and takin a short walk north-west.
On the lakes you can meet various species of local birds, from coots and duck to swans, storks and grey herons.
Birds of Bogensee
The area is covered in forests with occasional meadows and swamps.
It is a great place to escape from the urban life of Berlin into a fairly wild area, not very far from the town center, where one can rest among surrounding sounds and sights of nature.
The main attraction are the free ranging bulls, wandering about the area is a few herds. They are overall not aggressive and quite accustomed to meeting visitors, you must however remember basic rules of safety, like not cutting through the herd etc.
See my other entries on parks/nature in and around Berlin