Lesser Rhea (Rhea pennata) - BirdLife species factsheet

Lesser Rhea Rhea pennata

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Justification

Justification of Red List category
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (extent of occurrence <20,000 km² combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size has not been quantified, but it is not believed to approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

Population justification
The global population size has not been quantified. The subspecies pennata is described as locally fairly common (Schmitt et al. 2022). Considering the number of observational records (see eBird 2022), the population is likely very large.
The combined population of the two subspecies tarapacensis and garleppi is likely smaller. It has been suggested that the total population of both subspecies is as low as several hundred birds. In 1983, the Peruvian population was estimated at 18 individuals, with very low numbers in northern Chile (principally in Lauca National Park [A. Jaramillo in litt. 1999]) and on the altiplano in Bolivia. These figures are now generally thought to be too low, with 'at least many hundreds' in Chile from the Peruvian border to the Antofagasta highlands alone (A. Jaramillo in litt. 2014), while the population in Peru is estimated at 350 individuals (SERFOR 2018). A preliminary estimate is that the combined population of tarapacensis and garleppi could lie within the range 1,000-2,499 mature individuals, but this requires confirmation.

Trend justification
The species is suspected to undergo a decline, driven by habitat loss through conversion for agriculture and human settlements, overgrazing, hunting and egg-collection.

Distribution and population

Rhea pennata ranges from southern Peru to Patagonia in Chile. The nominate subspecies pennata is found from the Strait of Magellan and southern Chile to south-central Argentina. The subspecies tarapacensis is found in northern Chile, while the subspecies garleppi occurs from southern Peru through south-western Bolivia to north-western Argentina. A very small population of subspecies pennata was introduced to northern Tierra del Fuego (Schmitt et al. 2022).

Ecology

The subspecies pennata inhabits steppe, shrubland, shrub-steppe and mallines (successional wetlands with bog, meadows and ponds) (Bellis et al. 2006), up to 1,500 m, generally breeding in upland areas with bunch-grass (del Hoyo et al. 1992). The northern subspecies tarapacensis and garleppi inhabit deserts, salt puna, pumice flats, upland bogs and tola (Lepidophyllum) heath in altiplano at 3,000-4,500 m, down to 2,000 m in the eastern part of the range, and as low as 1,220 m in La Rioja (Argentina), where it frequents the monte desert ecosystem unique to Argentina (M. Pearman in litt. 2014).
It is typically found in groups of 5-30 individuals, with a male always accompanied by several females. During the breeding season the females lay up to 50 eggs in a single nest, which the male alone incubates. The species is fully herbivorous, feeding on leaves of herbs and shrub, fruits and seeds of grass (Marinero et al. 2017).

Threats

Hunting pressure for food and traditional medicine as well as the collection of eggs are thought to be the primary threats to the species (Borghi et al. 2017). Habitat loss and degradation through conversion for agriculture, grazing and expansion of human settlements may represent additional threats in parts of the range (Pedrana et al. 2011, Baldi et al. 2015).

Conservation actions

Conservation Actions Underway
CITES Appendix I (except nominate subspecies, which is on Appendix II). There has apparently been a captive breeding programme in Peru but it is not certain whether this has continued (J. Barrio in litt. 2014). It occurs in at least three national parks in Argentina (M. Pearman in litt. 2014). The species is listed as Critically Endangered at the national level in Peru (SERFOR 2018), as Vulnerable in Argentina (MAyDS and AA 2017) and as Endangered in Chile.

Conservation Actions Proposed
Quantify the population size. Monitor the population trend.
Maintain "mallín" (meadow) habitats in adequate condition as nesting sites (Bellis et al. 2006; Barri et al. 2008a, 2009). Prevent illegal hunting and egg-collecting, while developing alternative sustainable harvesting programmes (Barri et al. 2008a). Harvest "orphan eggs" (eggs sporadically laid outside nests) for use in captive breeding and reintroduction programmes (Barri et al. 2008b). Develop campaigns to raise awareness and reduce hunting, egg-collecting and the domestication of wild immature birds.

Acknowledgements

Text account compilers
Hermes, C.

Contributors
Barrio, J., Benstead, P., Capper, D., Jaramillo, A.P., Knapton, B., Mazar Barnett, J., Pearman, M., Sharpe, C.J., Symes, A. & Symes, A.

Recommended citation
BirdLife International (2024) Species factsheet: Lesser Rhea Rhea pennata. Downloaded from https://datazone.birdlife.org/species/factsheet/lesser-rhea-rhea-pennata on 22/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from https://datazone.birdlife.org/species/search on 22/11/2024.