Population Size and Distribution of the Chubut Steamer-Duck (Tachyeres leucocephalus) in Patagonia, Argentina

MARÍA LAURA AGÜERO; PABLO GARCÍA BORBOROGLU; DAN ESLER

Québec, Canadá

Conferencia; Third North American Sea Duck Conference; 2008

Canadian Wildlife Service, Environment Canada; Science & Technology, Environment Canada; Regroupement QuébecOiseaux

The Chubut Steamer-Duck (Tachyeres leucocephalus) is a flightless species endemic to the Central Patagonia marine coast of Argentina. In many ways, steamer-ducks are the ecological equivalent of North American sea ducks of the Tribe Mergini, occurring in nearshore waters where they dive to forage on benthic invertebrates. Also, like North American sea ducks, little is known about steamer-ducks and their low numbers make them a conservation concern. We present data from initial studies of steamer-ducks, and highlight how the research approaches and results from Sea Duck Joint Venture (SDJV) projects can be used to inform research and conservation of other species. As a first step, we present the first reliable population estimate, based on surveys conducted along 499 km of coast encompassing its main breeding area. To determine the best census technique we conducted both boat and ground counts along 36 km of coast. Numbers detected by boat surveys were 19% higher than ground census, overall. However, detectability differed among categories: boat census detected 70% and 75% more pairs and males, respectively, while ground census detected 9% and 5% more females and subadults, respectively. Using survey data and associated correction factors, we extrapolated calculated densities to unsurveyed sectors. We estimated that the total population size for the Chubut Province would not exceed 4700 individuals, with 33% (1565) represented by adults. This species has a restricted and non uniform distribution, with highest concentrations of individuals occurring at southern Chubut. Our study is the first to estimate Chubut Steamer-Duck abundance. All in all, has a multitude of implications regarding management strategies, habitat management goals and research objectives. A regular monitoring scheme and research program should be applied to assess the population health of this sea duck analog, and the successful efforts of the SDJV can be referenced to help direct these efforts.