Justification of Red List Category
This species's population size has declined rapidly over the past three generations and it therefore qualifies as Critically Endangered. It appears from recent counts that the population is now stable, probably as a result of extensive conservation actions. If evidence continues to show that the population remains stable, the species may be downlisted to a lower category of threat in the future.
In 2013, a simultaneous count across all plateaus known to have ever held grebes and visiting virtually every lake with historic records of the species, resulted 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). Surveys during the breeding season in 2015/2016, 2016/17 and 2017/18 counted 753, 749 and 776 adults, respectively (Roesler et al. 2016b, 2017, 2018b). The total population is therefore estimated at 650-800 mature individuals.
The population was estimated the population to number 3,000-5,000 individuals in the mid-1980s (Fjeldsa 1984). Following recent and rapid declines, more recent surveys estimated 1,000-1,200 individuals, roughly equivalent to 660-800 mature individuals, representing a population reduction of approximately 60-80% over three generation lengths. This estimate has been borne out by the breeding survey counts of 691 adults and 144 chicks in 2013 (Casañas et al. 2013), 771 adults and 138 chicks in 2014-15 (Roesler et al. 2015), 753 adults and 187 chicks in 2015-16 (Roesler et al. 2016b) and 749 adults and 130 chicks in 2016-17 (Roesler et al. 2017). By comparing the total counts made across the same 58 lagoons in 1984-5 (2,352 individuals) and 2010-11 (471 individuals), the overall population reduction was estimated at 80% over 26 years (Roesler et al. 2012, Roesler 2016), which is equivalent to a 73% reduction over three generation lengths. Nevertheless, it appears from recent counts that the population is now stable, probably as a result of extensive conservation actions.
This species breeds on a few basaltic lakes in the interior of Santa Cruz, extreme south-west Argentina. The only known wintering grounds are located at the estuaries of río Coyle, río Gallegos and río Chico on the Atlantic coast of Santa Cruz (Johnson and Serret 1994, Imberti et al. 2004, Roesler et al. 2011b). It is apparently a summer visitor in the Torres del Paine National Park in Magallanes, southern Chile, but there are no confirmed breeding records for the country (Roesler et al. 2011b, S. Saiter and F. Schmitt in litt. 2013, Donoso et al. 2015, Roesler 2015). The total population was estimated at 3,000-5,000 individuals in the mid-1980s, with half of these on Meseta de Strobel (Fjeldså 1984, O'Donnell and Fjeldså 1997). Counts on the wintering grounds suggest a decline of 40% over a period of seven years (S. Imberti in litt. 2006). Surveys conducted in December 2006 and January 2009, which 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). 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 have been real and rapid (Roesler et al. 2011b). 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). Comparing the total counts made across the same 58 lagoons in 1984-5 (2,352 individuals) and 2010-11 (471 individuals) suggests an overall population reduction of 80% over 26 years, most of which occurred in the Strobel plateau (Roesler et al. 2012, Roesler 2016). 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. Surveys during the breeding season in 2015/2016, 2016/17 and 2017/18 counted 753, 749 and 776 adults, respectively (Roesler et al. 2016b, 2017, 2018b).
During the breeding season, the species 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 Argentinian coast (Johnson and Serret 1994). Aquatic vegetation (mainly Myriophyllum elatinoides) on the breeding lakes is essential material for floating nests 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). The species breeds in colonies of up to 130 pairs from October to 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). Individuals tend to have a high fidelity towards the plateaus where they were born (Roesler et al. 2016).
The principal threats to the species appear to be introduced American Mink Neovison vison, salmon and trout and climate change (S. Imberti in litt. 1999, Imberti and Casañas 2010, Casañas et al. 2013, Roesler et al. 2015).
American Mink threaten the species at all stages of its life, with nests, chicks and adults all vulnerable to predation (Roesler et al. 2015, Fasola and Roesler 2018). In 2010-2011, an American Mink killed more than half the adults in a breeding colony of two dozen nests on the Buenos Aires plateau (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). Efforts to eradicate American Mink are complicated by its dispersal behaviour, with young males dispersing widely and re-occupying lakes (Fasola and Roesler 2018).
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 compete for food with the Hooded Grebe and modify lake conditions, increasing levels of cyanobacteria which may be harmful to grebes (Lancelotti et al. 2015, Roesler et al. 2015, Izaguirre et al. 2018, Francisco et al. 2019).
Surveys between 2006 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). Research has indicated that lower water levels exacerbate the detrimental impact of introduced fish on the lake conditions and thus on the grebes (Izaguirre et al. 2018). Given the small size of the population, the failure of an entire colony's breeding effort due to exceptionally high winds, as observed in 2013 at La Siberia, is another 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).
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 and attacks by Flying Steamerducks Tachyeres patachonicus (del Hoyo et al. 1992, O'Donnell and Fjeldså 1997, Imberti and Casañas 2010, Roesler et al. 2015). 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). Light pollution from cities, as well as oil exploitation and mining, may pose a threat on migration routes (Roesler et al. 2016b). Poor habitat conditions in breeding lakes may have increased competition for nest sites with other waterfowl species (Roesler et al. 2012, 2015). By-catch from fisheries may pose a threat in the winter range (Roesler et al. 2016b). The planned construction of two hydroelectric dams on the Santa Cruz River may cause changes to the species's wintering habitats and food availability, thereby threatening the species's wintering areas (Aves Argentinas 2016, Roesler et al. 2018a). Research has indicated that although the species winters at three estuaries, before returning to their breeding grounds they congregate at the Santa Cruz-Chico estuary, with almost 95% of the total population recorded there in August 2016 (Roesler et al. 2018a), meaning that any impact of dams on this estuary could have a great impact on the population.
Conservation Actions Underway
Aves Argentinas is Species Guardian for Hooded Grebe and, along with the local NGO Ambiente Sur, is coordinating the conservation effort. Patagonia National Park was created in 2014, covering 52,000 ha that includes over half of the breeding colonies (Roesler et al. 2015). 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. Surveys of the breeding population have taken place annually since 2009 (Roesler et al. 2018b). Surveys of wintering birds have been carried out along estuaries of the Atlantic coast (Roesler et al. 2015, 2018b). Research on the species's migration routes is underway, with the use of colour rings and GPS transmitters (Roesler et al. 2015, 2018b). Blood samples have been taken to perform genetic analyses and stable isotope analysis to better understand the species's diet.
'Colony Guardians' have been established with local communities (Roesler et al. 2016a). 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; recruitment is significantly enhanced at nests with Colony Guardians (Roesler et al. 2016a). 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, 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). Workshops have been held in 2014 and 2016 to provide updates on conservation work and engage with the scientific community (Roesler et al. 2015, Roesler et al. 2016b). 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). In August 2015, a 'Hooded grebe month' took place, involving educational, recreational, cultural and artistic activities (Roesler et al. 2016b). Teachers have been trained about the species's biology and threats (Roesler et al. 2016b).
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, 2016b). In 2014/2015, 40% fewer mink were captured compared to 2013/2014 indicating that these control measures were proving to be effective. A regulation has been passed banning the introduction of trout on the Buenos Aires plateau and a large number of trout have been removed from Laguna El Islote (Casañas et al. 2013, Roesler et al. 2018a). In 2015, Kelp Gull were controlled on the Buenos Aires plateau by shaking eggs to reduce breeding success (Roesler et al. 2016).
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 (Roesler et al. 2015), although by 2018 no captive-reared chicks had so far been released (Roesler et al. 2018a).
Experiments to prevent the loss of colonies to wave action during exceptionally strong winds have been undertaken, but were halted due to the risk posed to the grebes (Casañas et al. 2013, Roesler et al. 2018a).
Conservation Actions Proposed
Continue comprehensive surveys of breeding colonies and winter censuses of estuaries and unfrozen lakes. Expand the 'Colony Guardian' approach to all active colonies. 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. 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 Patagonia National Park, and more land is acquired (Roesler et al. 2015). Establish the species as a National Natural Monument (Roesler et al. 2015). Develop a captive breeding programme.
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
Mansur, E.F, Martin, R., Pilgrim, J., Wheatley, H., Ashpole, J, Bird, J., Symes, A., Sharpe, C.J., Butchart, S., Benstead, P., Capper, D.
Casañas, H., Imberti, I., Saiter, S. & Schmitt, F.
BirdLife International (2021) Species factsheet: Podiceps gallardoi. Downloaded from http://www.birdlife.org on 13/04/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 13/04/2021.