use of the before winter

[quazimahbub]

Dear Sir

which sentence is correct

The Cuckoo sing in winter

Cuckoo sing in the winter

Sincerely Yours

Mahbub

[Alan]

Actually, both versions are possible (i.e. with or without article) when, as here, reference is to the season in general.
When, however reference is to a season in a specific year, 'the' is obligatory.

Thus, compare

The cuckoo sings in (the) winter.

This year I took my paid leave in the summer, but next year I'm going to take it in the winter.