The Hooded Grebe: Endangered
From 14 and 25 January 2009, part of our staff participated on a field survey to gather information on the population trend of Hooded Grebe in Patagonia. Results will be published in at least one technical journal and several ornithological magazines.
The research team included 7 people belonging to two NGOs, Asociacion Ambiente Sur and Aves Argentinas, and was supported by the Pro Natur fund of Japan. Santiago Imberti, Martina McNamara, German Pugnali, Yayoi Sato, Andres Bosso, Andrea Pigazzi and Hernan Casañas are experienced birders and five of them had already been working with the species.
The main goal was to visit the two main known breeding sites. Laguna del Sello and surrounding ponds and the southern part of Strobel plateau, including Laguna del Medio or del Islote and adjacent ponds.
In January 2009 we visited a total of 25 ponds and lakes, which were potential feeding or breeding sites. Most of these sites had previous records of Hooded Grebe. We did not find any juveniles or nests and a total of 99 adults.
Based on the loose pieces of data gathered in the last 15 years and the information presented above we estimate a population size reduction of at least 50% over the last ten years.
Several threats have been listed for the Hooded Grebe. Among them, predation of eggs by Kelp Gull has been considered important. We recorded Kelp Gulls in both plateaus, being fairly common in the Lake Buenos Aires plateau.
The introduction of salmonids in some lakes and ponds may have changed the composition of the zooplankton and benthos of these water bodies. Laguna del Islote, in the Strobel plateau, used to have an important breeding population of the Hooded Grebe. We found no grebes there and very few birds in general.
In the Lake Buenos Aires plateau, in particular, the effects of Hudson Volcano's activity in August 1991 was evident. The information gathered from the local residents support this observation. In parts of the plateau the soil has been literally blown away and rests of volcanic ash cover large areas. This may have had a great impact on water communities, and especially for restricted range species such as the Hooded Grebe.
Another potential factor was the extremely low water level in most of the lakes and ponds. Some of ponds, where Hooded Grebe were recorded previously, have completely disappeared.
The data recorded, although not conclusive, strongly suggest that the Hooded Grebe could be in sharp decline and that its status was more severe than what the global category suggested (Near Threatened). Consequently, BirdLife International has decided to move it to the Endangered category.
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