Programa Pato-mergulhão - Instituto Terra Brasilis
www.terrabrasilis.org.br

SUMMARY

The Brazilian Merganser, Mergus octosetaceus, is considered critically endangered and one of the ten most threatened waterfowl worldwide (IUCN 2004, BirdLife International 2000).  Originally, its 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 almost non existent.

The Brazilian Merganser lives in remote and mountainous regions where it inhabits clean rivers and streams with river rapids and riparian vegetation (Partridge 1956, Silveira & Bartmann 2001).  It is recognized as a resident-species that does not abandon the watercourse of its established territory, and feeds on fish and aquatic invertebrates that it captures by diving in river rapids and backwater.  Preliminary studies indicate that the size of its territory varies between five and twelve kilometers (Silveira & Bartmann 2001).

The Brazilian Merganser is extremely sensitive to habitat loss and degradation.  The greatest threats to this species are increased river siltation caused by the expansion of cattle ranching, mining, watershed degradation and soil erosion.  Installation of hydroelectric plants is also a relevant factor and a constant threat.  Intensifying ecotourism, such as rafting, may become another threatening factor.

This project, partially funded by Ducks Unlimited, aimed to increase the knowledge on the distribution and habitat requirements of the Brazilian Merganser in the Serra da Canastra, Brazil.  Field surveys were conducted in 2004 and 2005 along several watercourses to map the occurrence of Brazilian Mergansers and to evaluate their habitat requirements.

Almost 150 kilometers of rivers were sampled.  A total of 23 Brazilian Mergansers were observed and 12 territories identified.  The environmental characteristics of the sampled sites in the same watercourse were highly variable, making it difficult to establish a pattern, or to detect the parameters on which the Brazilian Merganser is dependent.  Great structural variation was found among the sites sampled as well, including the type of riverbank vegetation and land use, as well as degree of conservation, occurrence of erosive processes, polluting sources, and width and depth of the watercourse.  Thus, further and more comprehensive studies are needed to identify the structural mosaic that defines Brazilian Merganser habitat.

Despite the stretches of degraded habitat found in some territories, the existence of well-preserved stretches with marginal vegetation seems indispensable for Brazilian Mergansers.  When disturbed or frightened, individuals seek shelter in the most protected portions of the watercourse within their territory.  This behavior is even more important when the pair is accompanied by young, emphasizing the need for well-conserved gallery forest habitat in the merganser’s territory.

RECOMMENDATIONS

The results of this study indicate the importance of the Serra da Canastra for the Brazilian Merganser, and support the urgent need to regulate and develop the expanding tourism activities in a sustainable manner that takes into account the conservation of this species and its habitat.

Farming, use of agro chemicals, and mining should be restricted where Brazilian Mergansers occur because of the negative impact of these activities on the rivers used by the birds, and their effect on the abundance of the merganser’s main food resource – fish.

Farmers play a crucial role in M. octosetaceus protection.  Therefore, their partnership in the development of actions to protect this species is of critical interest, including activities aimed at the conservation of water resources, creation of private reserves, and implementation of environmentally sustainable farming practices.

The Brazilian Merganser is an indicator of environmental quality and an important flagship species.  The conservation efforts aimed at this species will have a positive impact not only in the protection of water resources in this part of Brazil, but will also ensure the preservation of the quality of life of the local communities.

The amount of data gathered in recent years has contributed to a much better understanding of both the problems and the possible solutions.  However, a more detailed and systematic study of the biology and habitat requirements of the Brazilian Merganser is essential for the development of a comprehensive conservation action plan.

REFERENCES

•  BirdLife International. 2000. Threatened Birds of the World. Barcelona & Cambridge, UK: Lynx Editions & BirdLife International.
•  IUCN. 2004. 2004 IUCN Red List of Threatened Species. Gland, Switzerland and Cambridge, UK, IUCN.
•  Partridge, W.H. 1956. Notes on the Brazilian Merganser in Argentina. Auk 73: 473-488.
•  Silveira, L.F. & W. Bartmann. 2001. Natural history and conservation of the Brazilian Merganser Mergus octosetaceus at Serra da Canastra National Park, Minas Gerais, Brazil. Bird Conservation International 11: 287-300.