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| Brazilian merganser | |
|---|---|
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Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Anseriformes |
| Family: | Anatidae |
| Genus: | Mergus |
| Species: | M. octosetaceus |
| Binomial name | |
| Mergus octosetaceus Vieillot, 1817 | |
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TheBrazilian merganser (Mergus octosetaceus) is a South Americandiving duck in theMergus genus.It is one of the mostthreatenedwaterfowl species in the world, with possibly fewer than 250 birds in thewild and a small number kept incaptivity inBrazil[1] andCzechia.[2] It has a long, sharp-edgedbeak with a great number of tooth-like edges.
This merganser is a dark, slender duck with a shiny dark-green hood with a longcrest, which is usually shorter and more worn-looking in females. Upperparts are dark grey while the breast is light grey, getting paler toward the whitishbelly, and a whitespeculum is particularly noticeable in flight.[3]: 81796 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 to 56 centimetres (19 to 22 in) as an adult. Young Brazilian mergansers are mainly black with white throat and breast.
The Brazilian mergansers are generally silent birds, but may make barking calls in certain situations. Four calls have been recorded. A harshkrack-krack acts as analarm call emitted in flight. Males make a barking dog-like call, females make a harshrrr-rrrr and the contact call is a softrak-rak-rak. Ducklings give a high pitchedik-ik-ik.
Depending on the availability of suitable nesting and feeding sites, Brazilian merganser pairs occupy permanentterritories of 8-to-14-kilometre (5.0 to 8.7 mi) stretches of rivers.[1] Tree cavities, rock crevices, or disused burrows predominantly made byarmadillos are the ideal places for these mergansers to build theirnests. It is thought the breeding season is during theaustralwinter, 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 birdsincubate 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 information on this is presently speculative in nature.
Fish is the Brazilian merganser's main food, and they also eatmolluscs,insects and theirlarvae. The birds, usually in pairs, capture fish by diving in riverrapids and backwater.
The merganser population is believed to have less than 250 birds. Originally, the duck's geographical distribution comprised central-south Brazil and adjacent regions inParaguay andArgentina. Currently, all confirmed populations are located in Brazil and a more recent population inArgentina and information on most populations is very scarce. The Brazilian merganser population in theSerra da Canastra region is the most significant and best 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 theSerra da Canastra National Park. 70 birds have been seen near the park's headquarters in rio São Francisco. In Jalapão region are estimated 13 individuals in Novo river on 2009/2010 (four couples and some solitary adults).
In 2002, the species was also found on theArroyo Uruzu inMisiones, 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.[citation needed]
The slender Brazilian mergansers live in low densities in remote and mountainous regions where it inhabits clean rivers and streams with river rapids andriparian 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 does not abandon the watercourses where it established its territory. They do not move or want to move once their habitats have disappeared. The birds need large territories and their habitat is fast dwindling.
The Brazilian mergansers are very sensitive to habitat degradation and loss primarily due to human actions. A major threat to the birds' survival is the issue ofsilting of rivers caused by the expansion offarming activities,mining, watershed degradation andsoil erosion, as well asdeforestation.
Current traditionalsoil management and use practices in the region from farming may bring about serious damage regarding conservation ofnatural resources, especially water, on which the Brazilian mergansers and the farmers themselves are dependent. One of the farming practices here isshifting cultivation. It is common in the region to see farmers burning forest areas causing environmental damage to the natural vegetation and soils and the resident species.
A new threat to the species includes the installation ofhydroelectric plants. Hydropower plants are planned to be built in the same rivers that Brazilian mergansers have been found inParaná (rio Tibagi),Goiás (rio Paranã) andTocantins (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. The project has government backing in spite of the damage it may cause.[citation needed]
Dam-building has also become a major part in the disappearance of these birds. The filling of theUrugua-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 inBrazil andParaguay, where the Brazilian mergansers build their nests and lay their eggs.
Another threat to the Brazilian merganser istourism. The scenic beauty of Serra de Canastra National Park brings people from around the world to see theecotourism 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 ascanoeing andrafting disturb the natural habitats for the Brazilian mergansers that thrive on the rapid-rivers, interrupting breeding patterns. Water pollution and deforestation are also a concern as new facilities are built.
Other threats includeinbreeding,pesticides andpredation. Very few individuals survive from these threats and extinction may be imminent.[citation needed] People hunting the birds for food and collecting them for exhibition specimens contributed to the decline of the species.[4]
The Brazilian mergansercaptive-breeding program is led byItatiba Zooparque, azoo inItatiba,São Paulo state,Brazil.[5] The first collected eggs of Brazilian mergansers hatched in captivity in this zoo in 2011[6][7] and in 2017,Itatiba Zooparque announced the successful breeding of the first generation in captivity.[8] In 2020, they announced 15 new ducklings and for the first time, they had second-generation ducklings. For the first time, one female laid 7 fertilized eggs and they all hatched.[8] As of 2025, the only institution outside Brazil keeping Brazilian mergansers was thePrague Zoo, which received its first breeding group fromItatiba Zooparque in autumn 2023[9] and introduced them to visitors in 2024.[2] First five ducklings hatched inPrague in spring 2025.[9]
