Population trends and conservation of the endangered Hooded Grebe (Podiceps gallardoi)

ROESLER, I.; IMBERTI, S.; CASAÑAS, H.; MAHLER, B.; REBOREDA, J.C.

Cusco

Congreso; IX Congreso de Ornitología Neotropical; 2011

When the Hooded Grebe was first discovered in 1974 conservationists thought that there were no more than 150 individuals in only a few shallow lagoons on one plateau, thus it was considered endangered. Soon after, searches were conducted in western Santa Cruz which showed it was present on 90 lagoons with a total of 2691 individuals. The population was estimated to be around 3000-5000 and due to the apparent lack of major threats, it was downgraded to near-threatened. After two decades without monitoring, we conducted extensive searches during the breeding seasons of 2008/09, 2009/10 and 2010/11, covering 416 lagoons on 11 plateaus. We visited 65 lagoons out of the 90 where it was present in the 70’s and 80’s. Twenty of those lagoons were dry (or nearly) and at the remaining 45, that in 1984/85 season had 2056 individuals, we saw only 439 in 2010/11. This represents a decline of nearly 78% in 26 years. The highest decline was at the Strobel Plateau, (c. 95%) while at Buenos Aires plateau the population seems to remain fairly stable. All the previously mentioned threats are still present and some of them seem to have increased their impacts. We also found new threats including the presence of American Mink (Neovison vison) on the Buenos Aires plateau, where it killed at least 33 adults in one of the five colonies discovered during 2010/11. Those dead adults represent more than 3% of the species’ current population. Another new threat is the competition with other species of waterbirds for nest sites and nest materials, possibly caused by desiccation of many lagoons in the area. . We had recorded this competition with four different species so far. The amalgamation of all these negative factors seems to contribute to the strong decline of the Hooded Grebe.