Justification of Red List Category
This species has a very small and extremely rapidly declining population within a very small range. It is likely that birds may move between breeding sites on an annual basis but recent absences from former breeding sites are now believed to represent genuine declines. The species therefore qualifies as Critically Endangered.
O'Donnell and Fjeldsa (1997) estimated the population to number 3,000-5,000 individuals. The minimum population size, based on simultaneous winter counts during 2010-2011, is 759 (Roesler et al. 2011b). Following recent and rapid declines, and new surveys, the latest estimate is 1,000-1,200 individuals, roughly equivalent to 660-800 mature individuals, borne out by the comprehensive 2013 survey's total of 691 adults and 144 chicks (Casañas et al. 2013) and the 2014-2015 survey total of 771 adults and 138 chicks (Roesler et al. 2015).
Censuses on the wintering grounds indicated that the population may have declined by as much as 40% since the late 1990s. Assuming an exponential rate of decline this equates to an extremely rapid population decline of over 80 % over 21 years (three generations). This trend is also supported by recent surveys of the breeding grounds. During the winter counts of 2010 and 2011 no juvenile Hooded Grebes were observed (Roesler et al. 2011b).
This species breeds on a few basaltic lakes in the interior of Santa Cruz, extreme south-west Argentina; the only known wintering grounds are the río Coyle, río Gallegos and río Chico estuaries on the Atlantic coast of Santa Cruz (Johnson and Serret 1994, Imberti et al. 2004, Roesler et al. 2011b). It is apparently accidental in Magallanes, south Chile (Roesler et al. 2011b), however well-documented observations were made of two individuals using a lake in Laguna Blanca in October 2013 (Saiter in litt. 2013, Schmitt in litt. 2013). The total population was estimated at 3,000-5,000 individuals in 1997 with half of these on Meseta de Strobel (O'Donnell and Fjeldså 1997). Counts on the wintering grounds suggested a decline of 40% over a seven year period (S. Imberti in litt. 2006), and surveys conducted in December 2006 and January 2009 that revisited key known breeding sites surveyed in 1987 (Lagunas del Sello, del Islote and Tolderia Grande) and 1998 (Encadenadas) also found sharp declines; numbers fell from 452 to 51 at Laguna del Sello, from 700 to 0 at Laguna del Islote, from 90 to 0 at Tolderia Grande (H. Casañas in litt. 2009) and from 198 to 0 at Lagunas Encadenadas (Konter 2008). During the 2010-2011 breeding season 535 individuals were counted, indicating a population decline of more than 80% over the last 26 years (Roesler et al. 2011b).
In 2013, greater resources allowed a simultaneous count across all plateaus known to have ever held grebes and visiting virtually every lake with historic records of the species, resulting in a count of 691 adults and 144 chicks in 12 colonies (Casañas et al. 2013). During the summer of 2014/2015, 771 adults, 138 juveniles and 12 colonies were recorded across 18 lakes (Roesler et al. 2015). Three new lakes holding the species were identified, however on the Strobel plateau the number of lakes holding the species decreased. In both the 2009/2010 and 2010/2011 breeding seasons, the species was most abundant on three plateaus: Buenos Aires, Strobel and Siberia, with five lakes holding almost 85% of the population (Roesler et al. 2012). A population decline between 1984/1985 and 2010/2011 was not detected on the Buenos Aires plateau but there was a very strong decline (96%) on Strobel plateau (Roesler et al. 2012). While there is speculation that numbers fluctuate dramatically at breeding sites from year to year driven by movements rather than actual population fluctuations (Fjeldså 1986), overall declines detected on the wintering and breeding grounds appear to be real and rapid (Roesler et al. 2011b). Examination of photographs from the 1980s suggests that P. gallardoi was formerly the commonest waterbird on its core breeding grounds, the Buenos Aires, Strobel and San Martin plateaus; the 2009 surveys visited two of these areas and recorded the declines above as well as noting that a number of former breeding sites were completely dry.
During the breeding season, it inhabits basaltic lakes in the arid Patagonian steppes at elevations of 500-1,200 m (Chebez 1994); saline and bitter-salt lakes are used by non-breeding flocks and at least some birds wintering on the Argentine coast (Johnson and Serret 1994). Aquatic vegetation (mainly Myriophyllum elatinoides) on its breeding lakes is essential material for its floating nest and as habitat for several aquatic invertebrates that form its basic diet (Chebez 1994). During the first week after hatching, chicks are fed with aquatic beetles (Limnaea spp.) (Chebez 1994). It breeds in colonies of up to 130 pairs from October-March (Chebez 1994), but has an exceedingly low reproductive rate with an average of 0.2 young reared per adult per year (O'Donnell and Fjeldså 1997). However, while potential resources for breeding are apparently limited, the resources for adult survival appear to be plentiful and under natural circumstances adult mortality may be extremely low (O'Donnell and Fjeldså 1997). It occasionally establishes colonies in areas marginal to its main range (O'Donnell and Fjeldså 1997).
The two principal threats to the species appear to be climate change and the introduction of American Mink (Neovison vison) and of salmon and trout to private lakes on the Strobel plateau (S. Imberti in litt. 1999, Imberti and Casañas 2010, Casañas et al. 2013, Roesler et al. 2015). Recently the introduction of trout has been correlated with a decline in breeding numbers at certain lakes (S. Imberti in litt. 2006, Konter 2008). These exotic salmonids may compete for food with the species and modify lake conditions (Roesler et al. 2015). Surveys in 2006, 2009, 2010-2011 and 2013 found a number of lakes completely dry and water levels at known breeding sites were 2-3 m lower than in previous years (Konter 2008, Imberti and Casañas 2010, Roesler et al. 2011a, Casañas et al. 2013). Anecdotal reports indicated reduced winter snowfall without a corresponding increase in precipitation at other times (Konter 2008). Given the small size of the population however the failure of an entire colony's breeding effort due to exceptionally high winds, as observed in 2013 at La Siberia, is a potentially serious threat (Casañas et al. 2013). The apparent increase in the incidents of these exceptional winds over the last two decades (Roesler et al. 2015) may be related to overgrazing and/or climate change (Imberti and Casañas 2010).
American Mink threaten the species at all stages of its life, with nests, chicks and adults all vulnerable to predation (Roesler et al. 2015). In 2010-2011 an American Mink, a new arrival on the Buenos Aires plateau, killed more than half the adults in a breeding colony of two dozen nests (Roesler et al. 2011a). Further losses to lone mink occurred in 2012-2013, with 15 adults and 7 juveniles killed at El Cervecero and 10 adults and 5 chicks killed at the very remote C199 colony in La Siberia plateau (Casañas et al. 2013). Given that the Buenos Aires plateau currently holds a large proportion of the population, the presence of American Mink is a serious threat (Roesler et al. 2012). Furthermore, American Mink are known to exhibit 'surplus killing', which means that the presence of a single animal could result in the loss of whole grebe colonies (Roesler et al. 2015).
Excessive grazing by sheep (which causes erosion at lakeshores and limits the growth of emergent vegetation), predation by Kelp Gulls Larus dominicanus at some lakes, attacks by Flying Steamerducks (Tachyeres patachonicus) (Roesler et al. 2015), an inhospitable breeding climate and low breeding potential have been cited as threats (del Hoyo et al 1992, O'Donnell and Fjeldså 1997, Imberti and Casañas 2010), but the species's life history strategy is apparently well adapted to these conditions (Fjeldså 1986). The population may be limited by the carrying capacity of rather few lakes with good nest vegetation (O'Donnell and Fjeldså 1997). Volcanic eruptions in the breeding area may have a negative short-term effect because of heavy ash fall, but a long-term positive effect on the productivity of the wetlands (O'Donnell and Fjeldså 1997). There is oil exploitation on the potential migration route to the Atlantic (S. Imberti in litt. 1999). Poor habitat conditions in breeding lakes may have increased competition for nest sites with other waterfowl species (Roesler et al. 2012, 2015).
Conservation Actions Underway
Aves Argentinas is Species Guardian for Hooded Grebe and along with local NGO Ambiente Sur is coordinating the conservation effort. A law to create a new National Park was passed on March 14th 2013, covering 52,000 ha that includes over half of the breeding colonies. The final bill was passed on December 16th 2014, confirming Patagonia National Park as a protected area (Roesler et al. 2015). The park has one ranger and two fire rangers, all three have been involved in management tasks for the species. The site where the species was discovered in 1974, Laguna Los Escarchados, was declared a reserve in 1979 but is now known to hold only a marginal population (O'Donnell and Fjeldså 1997). Comprehensive surveys have taken place to locate all breeding colonies with ongoing monitoring to assess breeding success and mortality. In the winters of 2013 and 2014 surveys were carried out along estuaries of the Atlantic coast to assess wintering numbers (Roesler et al. 2015). 'Colony Guardians' have been established to work with local communities (Roesler et al. 2016). These are local people assigned to protect nests from predators, and to collect breeding data. Their efforts have improved survival rates at a number of colonies, with 60% nests successful when Colony Guardians were present (Anon. 2013); recruitment is significantly enhanced at nests with Colony Guardians (Roesler et al. 2016). During the 2014/2015 season, 11 individuals were colour ringed in order to understand their migration patterns (Roesler et al. 2015). Blood samples were also taken to perform genetic analyses and stable isotope analysis to better understand the species's diet.
An awareness-raising program has included displays and theatre productions within the region and the production of a video highlighting the plight of the species (available at http://www.youtube.com/watch?v=W0taBiJB35c&feature=youtu.be), which has been presented to over 100,000 people. An interpretation centre has been established at Río Gallegos, an important wintering area for the species (Roesler et al. 2015). A two day workshop was held in Buenos Aires in August 2014 to provide updates on the last five years work and engage with the scientific community (Roesler et al. 2015). Members of the Hooded Grebe Project have met with fishing, environmental and conservation agencies in Santa Cruz to inform them of key sites for the species to support decision-making (Roesler et al. 2015).
A monitoring protocol and control program for invasive species has been devised, targeting American Mink, Kelp Gulls (Stuart et al. 2013) and salmonid populations at breeding lakes and identifying routes of arrival. Work is ongoing to eradicate American Mink from the high plateau areas (Roesler et al. 2015). In 2014/2015, 40% fewer mink were captured compared to 2013/2014 indicating that these control measures are already proving to be effective. So far 71 mink have been removed from the Buenos Aires Lake Plateau and no further mink predation has been observed (Fasola & Roesler 2016). Experiments to prevent the loss of colonies to wave action during exceptionally strong winds have been undertaken and are ongoing (Casañas et al. 2013). A regulation has been passed banning the introduction of trout on the Buenos Aires plateau and a trout removal experiment has begun on the Strobel plateau to assess recovery times of the lake vegetation (Casañas et al. 2013). A captive rearing programme has been initiated near the Strobel Lake population, with the aim of raising wild eggs in captivity and releasing them back to Strobel Lake in order to boost the population which has been severely affected by the introduction of exotic salmonids (Roesler et al. 2015).
Conservation Actions Proposed
Continue comprehensive survey of breeding colonies and winter censuses of estuaries and unfrozen lakes. Expand the 'Colony Guardian' approach to all active colonies. Write and implement a species recovery plan. Eradicate American Mink from the high plateau areas and control the size of Kelp Gull colonies at key sites (Roesler et al. 2015). Extend the area ban on introducing salmonids to further breeding locations and work with landowners to raise awareness of the impacts of introducing salmonids. Study the species's ecology to understand population movements. Research on the species's migration is planned with support from the Zoological Society of London's EDGE of Existence programme and Cornell University (Roesler et al. 2015). Gather empirical data on population size and trends. Continue to investigate the threats to the species and the reasons behind recent declines. Investigate the threats to Hooded Grebes on the wintering grounds, particularly their interaction with fisheries (Roesler et al. 2012). Ensure that management activities for the species are implemented in the newly designated protected area, Patagonia National Park, and more land is acquired (Roesler et al. 2015). Establish the species as a National Natural Monument (Roesler et al. 2015).
c.32 cm. Unmistakeable, largely white with a dark grey back extending up the hindneck to its black head with contrasting white forehead merging into a reddish peaked forecrown. Extensive white in the flanks. Similar spp. Silvery Grebe P. occipitalis has less extensive white in the flanks. Its ear coverts are yellow and the front half of the face is grey rather than black. It lacks the peaked crown of Hooded.
Text account compilers
Benstead, P., Bird, J., Butchart, S., Capper, D., Mansur, E., Pilgrim, J., Sharpe, C J, Symes, A., Martin, R & Ashpole, J
Casañas, H., Imberti, I., Mazar Barnett, J., Roesler, I., Schmitt, F. & Saiter, S.
BirdLife International (2018) Species factsheet: Podiceps gallardoi. Downloaded from http://www.birdlife.org on 20/08/2018. Recommended citation for factsheets for more than one species: BirdLife International (2018) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 20/08/2018.