Holy Bat Trees Batman

One of our regular past times here in Chandigarh is to sit on our veranda at night and watch bats fly over our house. There is a steady, graceful procession of very large bats ( each about the size of a healthy ground squirrel ) every night from around 8PM until 9PM. They always fly from the west over our coti to the east, with one bat departing every minute or so. So for the past few months we've wondered where they are coming from, where they are going, and why they always fly east, and when, if ever, they fly back. While all of our questions remain questions, we recently stopped by Pinjore Gardens on our way home, and found an even more odd piece of information. I always assumed bats lived in caves and other dark places. Take a look at the photo below though. There were far too many to count -- relaxing, hanging from nearly every branch in a large, very exposed tree. These, at least to my untrained eyes, look just like the bats flying over our house. Any bat-ologists out there that can shed some light?