The bird sanctuary is essentially a large lake (about 30 acres) with trees (mangrove type). The best season to visit is Nov - Mar . I went in Dec 26th and there were thousands of birds. (How to get to Vedanthangal bird sanctuary: Part 1)
Essentially, you get to be in a long walkway around the lake (around 2~3 kms on either side of the entrance).
The birds are around 200 ~500 m away and on a clear day you wont have trouble seeing them. It is preferable to carry your telephoto lens or binoculars if you are keen on having a closer look.
There are two watch towers too from where you get to see the birds and the view is very scenic from there.
You can take a lot of pics when you go there. Some of my snaps are in
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