[order] ANSERIFORMES | [family] Anatidae | [latin] Merganetta armata | [authority] Gould, 1842 | [UK] Torrent Duck | [FR] Merganette des torrents | [DE] Sturzbach-Ente | [ES] Pato de los Torrentes (Arg), Pato Torrentero | [NL] Bergbeekeend | [copyright picture] Arthur Grosset
The Torrent Duck (Merganetta armata) is a member of the duck, goose and swan family Anatidae. It is the only member of the genus Merganetta. Today it is placed in the shelduck subfamily Tadorninae after the “perching duck” assemblage where it was formerly assigned to was dissolved because it turned out to be paraphyletic. Its closest relative may be the Blue Duck of New Zealand. The subspecies taxonomy is quite confusing. Males of the southern nominate subspecies, the Chilean Torrent Duck, have a grey back and blackish underparts with a chestnut belly. Males of the slightly smaller northern subspecies, the Colombian Torrent Duck, M. a. colombiana, are paler underneath, with steaked grey-brown underparts. Males of a third subspecies, the Peruvian Torrent Duck, M. a. leucogenis, are intermediate but very variable in plumage; some have entirely black underparts (turneri morph). Only males of the Chilean Torrent Duck have a black ‘teardrop’ mark beneath the eye. The Peruvian Torrent Duck is sometimes split into not less than 4 subspecies (leucogenis, turneri, garleppi and berlepschi), but these are more likely simply color variations, as they are not limited to distinct areas.
The Torrent Duck is highly sexually dimorphic. In contrast to most other ducks, the female is just as colorful as the male, but with an entirely different color scheme. Further, males show considerable geographic variation in head patterning and extend of black in the underparts whereas the female?s plumage remains the same throughout the range.
Listen to the sound of Torrent Duck
Copyright remark: Most sounds derived from xeno-canto
South America : Venezuela to Central Chile and West Argentina. The Torrent Duck is distributed in the Andes of South America from Venezuela and Colombia south to southern Chile and Argentina and into Tierra del Fuego.
The torrent duck exploits a difficult aquatic environment. Unlike most ducks, which seek calm waters, the torrent duck thrives on shallow, white-water rivers and streams. High-speed currents quickly wash nutrients downstream, and the waters are often heavily cobbled with rocks and boulders. As a result, food is scarce and difficult to reach. By adapting to exploit this niche, however, this duck has few competitors for food resources.
The torrent duck favors rivers and streams with areas of calmer water where it can take a rest between its demanding bouts of feeding.
The torrent duck is territorial throughout the year, which is uncomon in ducks. In keeping with such behavior, the male and female often pair for life, defending a stretch of river. Breeding start is geographically varied, begin February in Columbia. At the beginning of breeding season, both the male and female construct the nest with dry grass and line it with down and feathers. Nest sites vary from a cavity among rocks, on a cliff ledge or in thick streamside vegetation. Even the abandoned nest burrow of a ringed kingfisher may be used. The female incubates the clutch of 3-4 eggs for about six weeks. At hatching the young are boldly striped with black-and-white spots. They leave the nest within hours and have the swimming skills to feed in calm waters, though their buoyant down prevents them from diving. Juveniles are unlikely to find their own territory until they?re a year old. Both parents care for the young after hatching.
The diet of the torrent duck consists mainly of caddis-fly larvae, other aquatic insects, snails and a few fish. In the challenging mountain rapids, the duck uses various techniques to find food. Foraging mainly by day, the torrent duck dives into rushing rivers to search for food among the rocks and sieve through the bottom debris. In shallow water, it stands and dips its head below the surface to snap up invertebrates. In calmer waters, it up-ends, reaching down with its long neck to explore the streambed. It also feeds at the foot of a waterfall, with water crashing over its body, or climbs onto slippery ledges behind the cascade to feed among plants growing on the rocks.
copyright: Josep del Hoyo
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size may be moderately small to large, but it is not believed to approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
The torrent duck is not considered threatened, but is declining in many places, especially in the northern parts of its range. Its disappearance owes much to deforestation, which causes siltation – the lack of trees means that soil is washed away more easily.The increased runoff also causes flash floods, which destroy nesting sites.
Almost completely sedentary, the Torrent Duck remains close to its mate throughout its reproductive life, but young birds will range widely before establishing a territory.