I echo Roopak.

I have been so fortunate to have expert tracker belonging to Kadar tribe. He can identify ALL species, including subspecies through out the range - not only by seeing them, but also through calls, nests and even droppings.

Interestingly he was the tracker for Divya Mudappa, Sankaraman,Kannan, Poornima, Alphonse Roy, N.A.Naseer, S.U.Saravanakumar and a score of other wildlifers. Am sure that without his immense field knowledge many of them would'nt have had accomplished their missions. Divya Mudappa referred him to me.

Salim Ali's 12th edition is very good for its vivid description. Inskipp and Grimmet's edition is good especially for sub species.