A bird-watching tower can be seen across the lake; I'd recommend against going there, as the path to the right comes too close to the birds, and you'd only be likely to scare them to flight in their hundreds (or, in 1000's). The view from the tower would also be against the sun. It is a better idea to take the path to the left; here it winds behind the vegetatation, and, with some luck, you may come close enough to Sarus Cranes or storks, to have some decent shots. At the end of the path, in the distance to the left, there is an additional pond, which is often literally filled with spoonbills; do not try to approach here, but take a look with a scope instead.
Patna Sanctuary is best during the winter months; most of the birds tend to leave in March. Should you happen to be in the area, I'd definitely recommend it, particularly, if you have trouble finding birds elsewhere, due to the lack of water.
There's likely to be an abundance of birds, and the people are very friendly.
And should you happen to meet the chief wildlife warden, say hi from me.