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Hooded GrebePodiceps gallardoi
Authors: S. Imberti, H. Casañas, and Ignacio Roesler
Hooded Grebe is a near endemic species in Argentina with a local distribution in Santa Cruz province, southern Patagonia, where it is a breeding endemic. Records from southern Chubut province (Harris 2008) are not confirmed. There are very few records in Chile, including some sights from the Torres del Paine National Park area to the south, XII Región and some photographic evidence (R. Matus pers. comm.) and sight records (St. Pierre and Davies 1998) from Monumento Natural Laguna de los Cisnes in Tierra del Fuego.
During the breeding season its distribution extends over an area of high plateaus (the main ones are Buenos Aires, Asador, Strobel, Siberia, Cardiel Chico, Basáltica and Vizcachas) from 47° to 51° S at elevations varying between 500 and 1500 meters a.s.l., well to the east of the Andean range (Johnson 1997).
The main known wintering sites are on the estuaries of the Atlantic coast (Johnson and Serret 1994, Imberti et al. 2004), especially the Coyle and Gallegos estuaries which hold the greatest numbers (Imberti et al. 2004), with occasional records at Santa Cruz River and San Julián Bay (Johnson and Serret 1994). These areas hold less than 20% of the estimated population; the whereabouts of the rest of the population is only speculated upon. It has been suggested that they might use the Chilean fiords during this season (Fjeldså 1986, Johnson and Serret 1994) but a good search of the area yielded no results (Imberti 2005 and several pers. comm.). It is likely that most of the grebes are largely sedentary using the bigger lakes (Strobel, Quiroga, Sello, Islote among others) that do not freeze over during the winter. However, it also has been suggested that although they migrate to the coast, not all of the grebes enter the estuaries with the tides, but instead remain well offshore where they can not be accounted for (J. Fjeldså pers. comm.).
Little is known about the grebe's migration, as there are only a handful of records from intermediate areas. Grebes migrate down to the coast in April and remain there until August (Imberti et al. 2004). They are known to use a number of small lagoons as stopover (Johnson and Serret 1994, SI pers. obs.), where the numbers observed are regularly fewer than 20 individuals.
Distribution outside the Americas
Endemic to the Americas.
During the breeding season the Hooded Grebe favors a very harsh environment, the continuously storm battered small to medium size volcanic upland lakes that are surrounded by sheltering cliff walls, devoid of fringing reeds and deep enough to have clear water (Fjeldså 1986a, 1986b, Llimona and del Hoyo 1992). This habitat must be considered the most inhospitable in which a grebe possibly can breed (Fjeldså 1986). These lakes, depending on their level of water, present different amounts of the floating vegetation Myriophyllum elatinoides, which is used by the grebes to build their floating nests and also provides some protection from breaking waves. The amount of water covered by vegetation is crucial, for if there are not enough open leads to feed, the nesting attempts won’t be successful. Non breeders and young birds usually congregate in larger lakes, not necessarily clear or deep, with a high density of invertebrates (Beltrán et al. 1992) but without dense vegetation reaching to the surface (Fjeldså 1986b) where it is easier to feed.
At the end of the breeding season, presumably during their migration through the Patagonian steppe towards the coast, they have been observed in a number of smaller lagoons that are not very deep, with brackish, colored water and occasional patches of Myriophyllum elatinoides or similar floating vegetation (Beltrán et al. 1992, Imberti et al. 2004, SI pers. obs.). These are used for very short periods of time and never by large numbers of grebes.
During fall and winter (April-August) a percentage of the population moves to the Atlantic coast and mainly uses the estuarine areas of the Gallegos and Coyle rivers (Imberti et al 2004). These areas of brackish waters have some extreme tidal ranges of (up to 13 meters in the case of the Gallegos) and are very rich in resources, which might be the reason why the grebes use the strong currents in and out of the estuaries during the change of tides. The rest of the population is presumed to over winter nearby the breeding area, in the main lakes that do not freeze over: Strobel, Quiroga, Buenos Aires, Cardiel, Sello, Islote (Imberti et al. 2004).
Perhaps the first reference to the existence of Hooded Grebe went largely unnoticed for almost 100 years (Rumboll pers. com.). In 1902 H. Hesket Prichard, while traveling in Patagonia, wrote: “Here we camped and found yet another deep and rocky lagoon, on which were many divers which I could not identify”.
Hooded Grebe was only discovered for science as late as 1974 (Rumboll 1974) when a group of 150 birds was found at Escarchados Lagoon. The receding numbers of that population provoked more extensive searches by researchers from Fundación Vida Silvestre Argentina. The discovery of another group further north hinted at the fact that the Escarchados population was not a relict one and changed the search priorities. The need for establishing an estimate of the size of the population of the species was realized and field trips where organized during 1979 – 1987. The core of the population was established in the 1980’s, largely due to the efforts of the late Andrés Johnson and others (Bremer and Bremer 1984, Beltrán et al. 1992, Johnson 1985, 1986, 1997, Johnson and Serret 1994). Having established the breeding grounds, the question of the wintering grounds remained until part of the population was found wintering in the Atlantic coast (Johnson and Serret 1994). Further investigations were not carried out until the period 1999 - 2005, when Imberti et al. (2000, 2003, 2004, 2005) set out to survey a large portion of the coast of Santa Cruz province and the Chilean Fiords searching for other possible wintering sites.
No information available.
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