Tansa is a beautiful wildlife sanctuary very close to Mumbai/Thane. Its almost 3 times the size of Sanjay Gandhi National Park, Borivali, Mumbai, but seems to have lost all or most of its leopards to poaching, habitat loss, human encroachment etc.
I visited Tansa in September/October last year, right after the monsoons. Not a good time for bird sightings (I did see a small flock of what looked like the Cinereous Tits), but plenty of butterflies, insects, wild flowers.
(An earlier morning would have been better, but I reached at this time only)