Mohan,
For your info, I am quoting form Birds of South Asia The Ripley Guide by Pamela C. Rasmussen and John C. Anderton


Comb duck:
Sarkidiornis melanotos
Description:
A large heavy pied duck with black bill and legs, dark upperparts and white underparts. Breeding male has huge upright black ‘comb’ (fleshy protuberance) on bill (smaller in non-breeding season); white head and neck heavily freckled with black, and glossy black upperparts. Female is much smaller, without comb. Juvenile is dark brown on crown and upperparts, with dark line through eye and dingy, mottled underparts. Downy young is blackish above, and yellow below with short dark eyeline; yellow side-stripe. In flight wings are all dark and underparts all pale; some (either sex) have whitish lower back.

Occurs: Resident, with water-related movements, at least formerly from Lahore and SE Sind (Pakistan; probably extirpated) through N plains to Assam Valley, and in wooded tracts of Peninsula south to N Kerala; Sri Lanka (lowland dry zone, now only a vagrant). Scarce and local, in well-vegetated swamps, tanks and pools in wooded places.

Habits: Swims, perches and walks well; feeds by grazing or in shallows. Wanders widely in dry season, when may be found in flocks. Breeds in monsoon, often in small colonies, and several females may lay in one nest hole (usually in trees).

Cheers,
Sabyasachi