Its preferred habitat consists of wetlands with plentiful vegetation, including shallow lakes and paddy fields.

The downy grey ducklings leave the nest within a day or so of hatching, but the parents continue to protect them until they fledge around nine weeks later.

[2] They were an early split from the main duck lineage,[3] and were predominant in the Late Miocene before the subsequent extensive radiation of more modern forms in the Pliocene and later.

It has no recognised subspecies, although the birds in northern Mexico and the southern US have in the past been assigned to D. b. helva,[5] described as having paler and brighter underparts and a lighter crown than D. b.

[7][a] This led to the next available name proposed by French ornithologist Louis Pierre Vieillot in 1816 from a Paraguayan specimen as Anas bicolor.

[15] It is a long-legged duck, mainly different shades of brown; head, neck and breast are particularly rich buff (fulvous) with a darker back.

[5] There is a complete wing moult after breeding, and birds then seek the cover of dense wetland vegetation while they are flightless.

[19] These are noisy birds with a clear whistling kee-wee-ooo call given on the ground or in flight, frequently heard at night.

[20] The calls of males and females show differences in structure and an acoustic analysis on 59 captive birds demonstrated 100% accuracy in sexing when compared with molecular methods.

Adult birds in Asia can be confused with the similar lesser whistling duck, which is smaller, has a blackish crown and lacks an obvious dark stripe down the back of the neck.

In South America and Africa, juvenile white-faced whistling ducks are separable from fulvous by their dark crowns, barred flanks and chestnut breasts.

African birds move southwards in the southern summer to breed and return north in the winter, and Asian populations are highly nomadic due to the variability of rainfall.

[20] This species has strong colonising tendencies, having expanded its range in Mexico, the US and the West Indies in recent decades with northerly range expansions into California in late 19th century and rice-growing regions of the U.S. Gulf Coastal Plain in the early to mid-20th century, given its affinity for rice-growing areas.

[20][16] Breeding in the northern American region is restricted to the Gulf Coastal Plain of Texas and Louisiana and localities in southern California and south- and east-central Florida.

[5] The fulvous whistling duck is found in lowland marshes and swamps in open, rice fields, flat country, and it avoids wooded areas.

It flies at low altitude with slow wingbeats and trailing feet, in loose flocks rather than tight formation.

Foraging is by picking plant items while walking or swimming, by upending, or occasionally by diving to a depth of up to 1 m (3.3 ft).

[5] The International Union for Conservation of Nature (IUCN) estimates the population of the fulvous whistling duck to be from 1.3 to 1.5 million individuals around the world.

[20] A series of invasions from South America and reaching the eastern US commenced around 1948, fueled by rice cultivation, and breeding was recorded in Cuba in 1964,[19] and Florida in 1965.

[35] Outside North America it is subject to hunting for food or because of its liking for rice, and persecution means that it is now rare in Madagascar.

Pesticides used on rice fields may also have an adverse impact,[5] causing liver and breast muscle damage even at sub-lethal levels.