Critically Endangered (IUCN 3.1)
The Brazilian Merganser, Mergus octosetaceus, is a typical merganser.
The Brazilian Merganser, Mergus octosetaceus, is one out of six most threatened waterfowl in the world with possibly fewer than 250 birds thought to be remaining in the world today while none are kept in captivity. The origin of its name is from its long, sharp-edged beak that has a great number of teeth-looking edges.
This merganser is a dark, slender duck with a shiny dark-green hood with a long crest, which is usually shorter and more worn-looking in females. Upperparts are dark grey while the breast is light grey, getting paler toward the whitish belly, and a white wing patch is particularly noticeable in flight. It has a long thin jagged black bill with red feet and legs. Although females are smaller with a shorter bill and crest, both sexes are alike in color. The slender ducks range in size from 49 centimeters to 56 centimeters as an adult. Young Brazilian Mergansers are mainly black with white throat and breast.
The Brazilian Mergansers are generally silent birds, but they are known for making bark-like calls in certain situations. Four calls have been recorded. A harsh krack-krack¬ acts as an alarm call emitted in flight. Males make a barking dog-like call. Females make a harsh rrr-rrrr while a soft rak-rak-rak acts as the contact call. Ducklings give a high pitched ik-ik-ik.
Depending on the availability of suitable nesting and feeding sites, Brazilian Merganser pairs occupy permanent territories of eight to fourteen kilometer stretches of river. Tree cavities, rock crevices, or disused burrows predominantly made by armadillos are the ideal places for the merganser to build its nest. It is thought the breeding season is during the austral winter, when rain is minimal and water levels are low, but it may vary geographically. The Brazilian Merganser usually lays three to six eggs in June and July, with the chicks hatching during the following July and August. The young are capable of flight by September and/or October. Only the female birds incubate the eggs, but both parents care for the young. This is a very unusual behavior in ducks for both parents to help raise the young birds including direct provision of food to young. Adult Brazilian Mergansers are believed to remain on the same territory all year round, but there is not very much information about their movements and dispersal, so this currently remains on scientists' speculations.
Fish is the Brazilian Merganser main source of food. The birds capture the fish, usually in pairs, by diving in river rapids and backwater. Mollusks and insects and their larvae act as supplements to the birds' diet.
As pointed out earlier, the total world population for Brazilian Mergansers is believed to be 250 birds. Originally, the duck's distribution area comprised central-south Brazil and adjacent regions in Paraguay and Argentina. Currently, all confirmed populations are located in Brazil and information on most populations is very scarce. The Brazilian Merganser population in the Serra de Canastra region is the most significant and best well- known with populations occurring hundreds of kilometers away from each other. There are 47 individuals "? 28 adults and 19 young "? in the Serra de Canastra region as of 2006. Most Mergansers are found in the Serra de Canastra National Park, where 70 birds have been seen near the park's headquarters in rio São Francisco.
In 2002, the species was also found on the Arroyo Uruzu in Misiones, Argentina, the first record in the country for ten years, despite extensive surveys done by local researchers conducted throughout previous years. The bird was last reported seen in 1984 in Paraguay, where very little habitat remains; however some local reports show that a few individuals may still be living in the area.
The slender Brazilian Mergansers live in low densities in remote and mountainous regions where it inhabits clean rivers and streams with river rapids and riparian vegetation. Brazilian Mergansers are very territorial birds defending large stretches of river and the land surrounding the fast-flowing water. They are recognized as a resident species that do not abandon the watercourses where it established its territory, which some think is a reason the birds are endangered. They don't move or want to move once their habitats have disappeared. The birds need large territories and their habitat is fast dwindling into nothing making the Brazilian Merganser hard to find.
The Brazilian Mergansers are extremely sensitive to habitat degradation and loss primarily due to human actions. A major threat to the birds' survival is the issue of silting-up of river water caused by the expansion of farming activities, mining, watershed degradation and soil erosion, as well as deforestation.
Current traditional soil management and use practices in the region from farming may bring about serious damage regarding conservation of natural resources, especially water, on which the Brazilian Mergansers and the farmers themselves are dependent on. The farmers use a practice called slash-and-burn. It is common in the region to see farmers causing extensive and uncontrollable burnings causing serious environmental damages to natural vegetation and soils and the species that make the area their home.
A new threat to the species includes the installation of hydroelectric plants. Hydropower plants are planned to be built in the same rivers that Brazilian Mergansers have been found in Paraná (rio Tibagi), Goiás (rio Paranã) and Tocantins (rio Novo). The hydropower plants are a major threat to the birds' survival because the plants transform systems such as creeks, rivers and streams into turbid lake systems. Backed by minister Dilma Roussef, a former communist guerilla, supports government policies creating hydropower no matter how damaging the plants may be to the environment. There is a very real chance the Merganser populations may be lost due to development.
Dam-building has also become a major part in the disappearance of these birds. The filling of the Urugua-i reservoir, which took place between 1989 and 1991, had a major impact on Brazilian Mergansers in Argentina. The population declined drastically when its fast-flowing rivers were turned into large lakes. After the Urugua-i dam was built, the birds have only been seen on the Uruzu stream, a tributary of the Urugua-i. The dams flood suitable habitat, especially in Brazil and Paraguay, where the Brazilian Mergansers build their nests and lay their eggs.
Another threat to the Brazilian Merganser is tourists. The scenic beauty of Serra de Canastra National Park brings people from around the world to see the ecotourism landmark. Tourists are attracted to the abundant supply of clear water with over 150 waterfalls in the area. Sporting activities also create a disturbance for the Brazilian Mergansers. Activities such as canoeing, rafting, etcetera disturb the natural habitats for the Brazilian Mergansers that thrive on the rapid-rivers. With the activities being haphazardly practiced and the increasing amount of facilities being built on the margin of the rivers, they may cause serious threats to the Brazilian Mergansers populations. It disturbs the area of use and their breeding patterns and its habitat due to water course pollution and deforestation.
Other threats include birds inbreeding and humans competitively hunting the birds, egg-collecting and pesticides and predation. Very few individuals survive from these threats and extinction may be imminent. People hunting the birds for food and collecting Brazilian Mergansers for exhibition specimens are also believed to have contributed to the species decline.