3.5.1 Dendrocygna (Autumnalis, bicolor and viduata) (whistling ducks)
3.5.2 Cairina moschata (Muscovy duck)
Ducks, geese and swans (Order Anseriformes, Family Anatidae) are a much sought after and valuable resource, particularly for sport hunters (Table 20). Fully 62 of the 147 known species (578) are found in Latin America (59, 336, 618), including 16 species migrating from the north. Roughly half of the resident species are confined to southern South America and/or the Andes, and are particularly abundant in the wetland areas of the Pampas (618). Some species are widely distributed throughout tropical America such as Dendrocygna (three species) Neochen jubata, Anas bahamensis, Amazonetta brasiliensis, Sarcidiornis melanotus, Cairina moschata and Oxyura dominica.
Migratory ducks are important in Mexico which had an estimated 2.5-3.2 million in 1952 (336), and 4.78 million in 1981 (388). Over half a million are taken each year (24, 336). Anas acuta is the most numerous species. Southward toward Central and South America, the number of migratory species drops off. Only Anas discors overwinters in vast flocks in South America, providing good hunting, particularly in the coastal regions as far south as Peru and northeastern Brazil. The whistling ducks (Dendrocygna) and Muscovy ducks (Cairina moschata) are far and away the most valuable native neotropical ducks, and they deserve to be treated in greater detail.
Local names (generic): Guire, guirirí (Venezuela); iguasa (Colombia); iraré (Brazil); koneja (Suriname); ouikiki (Trinidad); pato silbador (Venezuela); pato silbón or sirirí (Argentina, Uruguay, Chile), piche (Costa Rica, El Salvador); pichichi or pijijí (Mexico, Guatemala); yaguaso (Venezuela).
Geographical variation and distribution: The genus is circumtropical. D. autumnalis is distributed throughout the American continent from southern Texas to Ecuador, northern Argentina and southern Brazil. D. bicolor is found from California and Texas to Peru and Argentina (though apparently absent in Amazonia). D. viduata ranges from Costa Rica to Peru and Argentina (59). The fourth American species is D. arborea, found in Cuba and other Caribbean islands, and listed as vulnerable by the IUCN.
Elevational range: Whistling ducks inhabit the lowlands but are occasionally found in mountain lagoons, such as D. viudata for which the record altitude is 1 500 m (389).
Size and weight: These are medium-sized ducks with no sexual dimorphism, a total length of up to 48 cm, and weighing 600-900 g. The somewhat smaller D. viudata. 43 cm long, weighs up to 700 g (235, 238, 336, 363, 383).
Habitat: Whistling ducks are found in wetlands, estuaries, brackish lagoons with aquatic vegetation and along the shores of rivers, being most abundant in flooded savannahs and irrigated rice fields. The three species may share the same general habitat, but D. bicolor will be found in the more aquatic sites and D. autumnalis is more of a land-dweller. The construction of irrigation systems and dams seems to favour whistling ducks and greatly expand their regional distribution (67, 70, 238, 336, 358, 363).
Abundance: Whistling ducks can be very abundant in the right habitat. The total estimated duck population in the rice-growing areas of Venezuela is 200-400 000 (238). D. autumnalis is probably the most abundant neotropical duck (67, 70, 232, 336, 381).
Behaviour: Whistling ducks are highly gregarious. Outside the pairing season, they may band together in flocks of hundreds or thousands. They spend most of the day resting on the banks of the estuaries, lagoons and occasionally in the trees along the river bank (D. autumnalis), feeding mainly at night. They fly regularly between their feeding and resting areas at twilight or at night, their presence revealed by their characteristic whistles. They are naturally fairly tame but can be very shy when heavily hunted. Highly mobile, they can easily move from one region to another and the populations of southern America and Mexico seem to be at least partly migratory (24, 146, 336, 519).
Feeding habits: They feed primarily on aquatic grass seeds, and on rice and aquatic weeds in the rice fields, rounding out their diet with insects or molluscs, particularly during the mating season. The three species have rather similar diets and are fairly unspecialized feeders (70, 236, 336, 363).
Reproduction: They nest during the rainy season from June to August in Mexico and Central America (24, 336, 519), from July to September in Venezuela (232, 363), and from November to January in Argentina (146, 433). 232, 336, 578). The chicks reach adult weight and plumage in six to seven months and can reproduce at the age of one year (236).
Hunting: Whistling ducks are stalked until they take wing, or the hunter may wait until the flock flies over, concealed in strategic spots or "blinds" (67, 379). The legal whistling duck kill in the rice fields of Venezuela ranged from 38-118 000 ducks each year between 1967 and 1981 (1.06-3.76 ducks/day/hunter) between 1967 and 1981 (238). A very high portion of the kill (9-30 percent) is not recovered, depending on the species and site (358). Peasants in the llanos region and in Brazil are in the habit of capturing large numbers of moulting ducks and sub-adult chicks that are unable to fly (238, 440, 535).
Products: The meat of these ducks, tasty if a little tough, is much appreciated. The eggs are also gathered and eaten.
Management: Whistling ducks are a very valuable game and food resource in tropical America. Some populations, particularly in Mexico and Central America, are thought to be dropping in numbers under hunting pressure. D. bicolor is apparently the most vulnerable of the three (336, 383). These birds also congregate in massive flocks in the rice fields and may be considered farm pests under certain circumstances (70, 183, 238).
They are widely distributed, abundant and prolific game birds, tolerant of changes in habitat and agro-ecosystems, highly prized as food and relatively easy to hunt. Whistling duck management therefore deserves priority. Studies are needed on their regional mobility, particularly studies focusing on the possible "funnelling effect" of the rice fields.
Captive breeding: Whistling ducks can easily be bred in captivity (232, 432, 578) and are frequently co-reared with poultry in rural areas of the neotropics. The eggs are usually collected from nests in the wild and set under hens to brood.
Local names: Bosdoks (Suriname), pato criollo (Argentina, Uruguay), pato do mato (Brazil), pato perulero (Mexico), pato real (several countries).
Geographical distribution and variation: From Sinaloa and Tamaulipas on the west coast of Mexico down through Central America to Ecuador on the Pacific coast and Uruguay and northeastern Argentina in the south. There are no subspecies (59, 578).
Elevational range: C. moschata is confined to the tropical belt up to 800 m (238).
Size and weight: These are among the most corpulent ducks in America: sexual dimorphism is marked: the adult male measures 76-86 cm and weighs 2-4.5 kg, and the female 53-63 cm and 1-2 kg (36, 59, 336, 383. 399).
Habitat: Muscovy ducks can be found in forest or savannah habitats, around estuaries, lagoons or rivers, and sometimes in very tiny bodies of water in tropical forests (67, 134, 221, 336, 399).
Abundance: Originally abundant in favourable habitats but currently scarce over most of their range (238, 336, 383, 399, 519).
Behaviour: Muscovy ducks live alone or in groups of four to twelve, rarely in large flocks. They are mainly active in the morning and afternoon, feeding on the shores of brackish waters, or in the flood savannah and underbrush. They often sleep at night in permanent roosts in trees along the river bank. Heavy and low-flying, they are silent and timid (36, 238, 336, 383, 399).
Feeding habits: Their diet consists of seeds, roots, aquatic plants, insects and other invertebrates and fish (36, 232, 336, 383, 399). No detailed studies of their diet appear to have been made.
Reproduction: Muscovy ducks are polygamous, nesting in hollow trees and apparently mating mostly at the onset of the rainy season (in Venezuela from the end of the dry season in March up to August) (399). Clutch size ranges from eight to 15 eggs, which are incubated for 35 days by the female (336, 399, 578).
Hunting: Muscovy ducks are hunted with shotguns close to their roosts or along the flight-lines linking the feeding to the resting areas (67, 238, 336, 379, 399).
Products: Muscovy duck meat is red and gamy. Its size and the quality of its meat make it the preferred tropical game duck.
Management: C. moschata is persecuted by all types of hunters and its populations are dropping fast due to overhunting and deforestation of its habitat. This is a species of great value which tolerates modified environments but is in urgent need of hunting regulation measures such as closed seasons and bag limits (238, 336, 383, 578). Studies are also needed on Muscovy duck biology, as the available information on the species is primarily anecdotal.
Captive breeding: C. moschata was domesticated in pre-Colombian times and is domestically reared in many countries of the world (399, 432, 578). It is the only truly domesticated South American bird.