Abstract
The Brazilian Merganser is a threatened species and classified as Critically Endangered. Its world population is estimated to be fewer than 250 individuals surviving in the wild. Currently, the species is known from disjunct populations distributed in the states of Minas Gerais, Goias, and Tocantins (in the Jalapao region). For this study, the stretches of the Preto, Novo, Soninho, and Sono Rivers were surveyed by airboat to better estimate the species distribution in the region. Brazilian Mergansers were found only on the Novo River along a stretch upstream from Da Velha waterfall. Four pairs and a few other adult individuals were identified there. A 50 km stretch of the Novo River was selected for monthly censuses (n = 13) from August 2009 to October 2010 to estimate the relative abundance and population size of the Brazilian Merganser. The Abundance Kilometric Index was 0.125 individuals/ km. The Novo River, from Da Velha waterfall until near its headwaters, is 145 km long and our survey estimated a population of 13.7 individuals. Changes caused by uncontrolled tourist activities on the Novo River, such as rafting during the species’ breeding season, riparian forest deforestation, and proposed hydropower projects, can negatively impact this small Brazilian Merganser population putting it in great risk of local extinction.
Highlights
The Brazilian Merganser (Mergus octosetaceus Vieillot, 1817) is a globally and locally endangered species (MMA 2014, IUCN 2015)
Relative abundance of Brazilian Mergansers along the Novo River was estimated using the Kilometrical Abundance Index (KAI) (Telleria 1986), which consists of determining the number of individuals detected per kilometer of survey; here we considered only adult individuals detected on the census section (50 km)
Brazilian mergansers were recorded only in the Novo River at the section located above the Da Velha waterfall; no records were obtained along the Preto, Soninho and Sono rivers
Summary
The Brazilian Merganser (Mergus octosetaceus Vieillot, 1817) is a globally and locally endangered species (MMA 2014, IUCN 2015) It is one of the most threatened waterfowl species of the Neotropical region (Bartmann 1988, Collar et al 1992), with probably less than 250 individuals surviving in the wild (Birdlife 2015). Its nests are made in tree or rock cavities (Bruno et al 2010, Barbosa et al 2011) right beside water bodies (Lamas & Santos 2004), and its breeding season usually ranges from June to September. It inhabits only shallow, clear water rivers or small streams, with stretches of rapids, and bordered by riparian vegetation. Due to its low population densities and high sensitivity to environmental disturbance, the species is most threatened by the loss of suitable habitat and/ or reduction of water quality, complicating the species’ conservational status
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