It is saying incorrect if I write 'Birds are going to south'......why?
I think you need to type "to the south" if you're going to use "to" at all.
Good question, but your sentence is not standard English. As Lady Nurington says, standard English is "going south" ("south" is an adverb) or "going to the south" ("south" is a noun).
thanks..........i am not native english speaker so the question arrived