 Adult birds in Asia can be confused with the similar lesser whistling duck , although that species is smaller , has a blackish crown and lacks an obvious dark stripe down the back of the neck . Juvenile fulvous whistling ducks are very like young lesser whistling ducks , but the crown colour is still a distinction . Juvenile comb ducks are bulkier than whistling ducks and have a dark cap to the head . In South America and Africa , juvenile white @-@ faced whistling ducks are separable from fulvous by their dark crowns , barred flanks and chestnut breasts . 
