Distinctive dark maroon wing coverts are hard to see but visible on the folded wings in this photo. These patches are usually concealed behind body feathers. This is a close relative of the widespread Fulvous Whistling-Duck (D. bicolor). Their ranges overlap in eastern India, but only the Lesser occurs regularly at Bharatpur. The two are similar but Lesser is smaller and lacks the white uppertail coverts of Fulvous. Lesser Whistling-Ducks are largely nocturnal, roosting near wetlands during the day but foraging in paddyfields at night. Males and females are similar. Canon PowerShot SX50 HS
References:
Ali, S & SD Ripley (1987). Compact Handbook of the Birds of India and Pakistan. Edition 2. Oxford University Press.
Carboneras, C. & Kirwan, G.M. (2016). Lesser Whistling-duck (Dendrocygna javanica). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from http://www.hbw.com/node/52798 on 22 June 2016).
Rasmussen, P.C. & Anderton, J.C. (2005) Birds of South Asia. The Ripley Guide. Vols. 1 and 2. Smithsonian Institution & Lynx Edicions, Washington, D.C. & Barcelona.