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Version 1.0

This is a historic version of this account.  Current version


Hooded Grebe Podiceps gallardoi

S. Imberti, H. Casañas, and Ignacio Roesler
Version: 1.0 — Published August 27, 2009


Due to the negative results of the winter counts made between 1998-2004 (Imberti et al. 2004), and of an extensive search in several breeding areas during the summer of 2009 (which included the lagoons that held 40% of the estimated population in the 1980’s; Imberti et al. 2009 in litt), the conservation status of the Hooded Grebe recently has been upgraded to ‘Endangered’ (BirdLife International 2009). Reflecting on these results, BirdLife International (2009) indicates that it is likely that birds move between breeding sites on an annual basis, but recent absences from former breeding sites are now thought to represent genuine declines.

Although it has been suggested that this species often skips breeding seasons, and that, for each pair, a few years may elapse between each successful breeding (Fjeldså 2004, pers. comm.), the low numbers found in the surveys seem at odds with this explanation. Having spent a good part of the 2008/9 season visiting these lagoons, a fact that quickly becomes apparent is that no nests, chicks or immatures of Hooded Grebe were observed in any of the 50 plus sites visited. This is a situation that repeats itself as we review our notebooks from the last decade, when these breeding events seem to have become less and less common, the last big breeding season observed having taken place some six years ago. Perhaps a strategy that helped the species survive by reducing its numbers in years of lack of resources and increasing in the good ones has been pushed a bit over the limit of sustainability by our modification of the environment? (SI, HC).

Effects of human activity on populations

No direct effects of human activity over the grebe’s population have been proven with certainty, aside from the illegal killing of a few individuals.

Major considerations should be taken regarding the indiscriminate introduction of trout on the breeding grounds: since the Hooded Grebe is such a specialist, any change in the composition or nature of the environment likely will affect the grebe earlier than other species. The introduction of trout seems to be the most important local human induced change.

On a larger scale, a factor that is common throughout all the plateaus is the low water level in the lagoons, and the large number of smaller basins that are completely dry. This could potentially explain the low numbers of grebes detected everywhere when compared with the 1980’s. If the trend of dry winters continues, a minimum threshold might be reached for the species: their ability to switch from lake to lake until they find a suitable one to breed might not be enough to sustain a viable population.

Recommended Citation

Imberti, S., H. Casañas, and I. Roesler (2009). Hooded Grebe (Podiceps gallardoi), version 1.0. In Neotropical Birds Online (T. S. Schulenberg, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/nb.hoogre1.01