Archived 2014 discussion: Lesser Rhea (Rhea pennata) is being split: list R. tarapacensis as Endangered?

This is part of a consultation on the Red List implications of extensive changes to BirdLife’s taxonomy for non-passerines

Lynx Edicions and BirdLife International will publish the HBW-BirdLife Illustrated Checklist of the Birds of the World in 2014, building off the Handbook of the Birds of the World series, and BirdLife’s annually updated taxonomic checklist.

The new Checklist will be based on the application of criteria for recognising species limits described by Tobias et al. (2010). Full details of the specific scores and the basis of these for each new taxonomic revision will be provided in the Checklist.

Following publication, an open and transparent mechanism will be established to allow people to comment on the taxonomic revisions or suggest new ones, and provide new information of relevance in order to inform regular updates. We are also actively seeking input via a discussion topic here regarding some potential taxonomic revisions that currently lack sufficient information.

The new Checklist will form the taxonomic basis of BirdLife’s assessments of the status of the world’s birds for the IUCN Red List. The taxonomic changes that will appear in volume 1 of the checklist (for non-passerines) will begin to be incorporated into the 2014 Red List update, with the remainder, and those for passerines (which will appear in volume 2 of the checklist), to be incorporated into subsequent Red List updates.

Preliminary Red List assessments have been carried out for the newly split or lumped taxa. We are now requesting comments and feedback on these preliminary assessments.

Lesser Rhea Rhea pennata is being split into R. pennata and R. tarapacensis, following the application of criteria set out by Tobias et al. (2010).

Prior to this taxonomic change, R. pennata (BirdLife species factsheet) was listed as Near Threatened under criteria A2cd+3cd+4cd, on the basis that it was suspected to be in moderately rapid population decline (approaching 30% over three generations, estimated by BirdLife to be c.33 years in this species), owing to habitat loss, hunting and egg-collection.

R. tarapacensis (incorporating garleppi) occurs in extreme southern Peru, north-eastern Chile, western Bolivia and north-western Argentina, where it inhabits deserts, salt puna, pumice flats, upland bogs and heathland at 3,500-4,500 m (Davies 2002). The species is subjected to high hunting pressure and poaching of eggs, as exacerbated by road construction, and it has been noted to be in decline (Davies 2002 and references therein). There appears to be little up-to-date information available on the species’s population size and rate of decline, although it has been noted that it may qualify as Vulnerable or Endangered (del Hoyo et al. 1992, Davies 2002).

Populations of all forms in the R. pennata complex have declined markedly in recent decades and the northern subspecies are said to be in serious danger of extinction (Folch 1992). The combined population of tarapacensis and garleppi has been estimated at several hundred birds, with the healthiest populations in Argentina (densities at two sites of 2-5 birds/km2) (Chebez 1994). 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.

This information implies that R. tarapacensis could qualify as Endangered under criterion C2, on the basis that its population includes fewer than 2,500 mature individuals and is inferred to be in continuing decline. However, additional information is required on the species’s likely subpopulation structure (i.e. the number of mature individuals in the largest subpopulation or the percentage of all mature individuals in one subpopulation), where subpopulations are defined as geographically or otherwise distinct groups in the population between which there is little demographic or genetic exchange (typically one successful migrant individual per year or less).

Further information is also requested on this species’s rate of population decline over a period of 33 years (estimate of three generations), stretching into the past or future. Any evidence of a population decline approaching or exceeding 30% over the past or next 33 years will likely qualify the species for listing as Near Threatened or Vulnerable, respectively. A decline of at least 50% over this period would probably qualify the species as Endangered.

R. pennata (as defined following the taxonomic change) is found in southern Argentina (introduced to Tierra del Fuego in 1936) and south-eastern Chile, and inhabits shrub-steppe and floodplain grasslands from sea-level to 2,000 m (Davies 2002). It is characterised as still fairly common (del Hoyo et al. 1992, Davies 2002). Hunting and egg-collection are threats to this species, with overgrazing perhaps being less significant but still having a negative impact (Barri et al. 2008). Captive breeding projects are taking place for conservation and commercial reasons (F. Barri in litt. 2012). It is thought likely that the species will qualify as being of Least Concern, on the basis that it is not thought to approach the thresholds for Vulnerable under any of the IUCN criteria; however, any evidence of a population decline approaching or exceeding 30% over the past or next 33 years (estimate of three generations) will likely qualify the species for listing as Near Threatened or Vulnerable, respectively. Comments and further information are invited.


Barri, F., Martella, M. B. and Navarro, J. L. (2008) Effects of hunting, egg harvest and livestock grazing intensities on density and reproductive success of lesser rhea Rhea pennata in Patagonia: implications for conservation. Oryx 42(4): 607-610.

Chebez, J. C. (1994) Los que se van: especies argentinas en peligro. Buenos Aires: Albatros.

Davies, S. J. J. F. (2002) Ratites and Tinamous: Tinamidae, Rheidae, Dromaiidae, Casuariidae, Apterygidae, Struthionidae. Oxford, UK: Oxford University Press (Bird Families of the World Series).

del Hoyo, J., Elliot, A. and Sargatal, J. (1992) Handbook of the birds of the world, vol 1: Ostrich to Ducks. Barcelona, Spain: Lynx Edicions.

Folch, A. (1992) Rheidai (Rheas). Pp. 84-89 in del Hoyo, J., Elliott, A. and Sargatal, J., eds. Handbook of the birds of the world. Barcelona, Spain: Lynx Edicions.

Tobias, J. A., Seddon, N., Spottiswoode, C. N., Pilgrim, J. D., Fishpool, L. D. C. and Collar, N. J. (2010) Quantitative criteria for species delimitation. Ibis 152: 724–746.

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6 Responses to Archived 2014 discussion: Lesser Rhea (Rhea pennata) is being split: list R. tarapacensis as Endangered?

  1. Few years ago the Wildlife office in Peru (DGFFS), under Agriculture, had a captive rearing program on R. tarapacensis. I think it failed, but it would be good to contact the head of the office (EDIT: EMAIL ADDRESS REMOVED) to know what happened. On a personal view, there are more than just 18 individuals in Peru, but the Peruvian population is indeed Critically Endangered. Worst than hunting is egg collection.

  2. Joe Taylor says:

    Preliminary proposals

    Based on available information and comments posted above, our preliminary proposals for the 2014 Red List would be to treat:

    R. pennata as Least Concern

    R. tarapacensis as Endangered under criterion C2a(ii)

    There is now a period for further comments until the final deadline of 31 March, after which recommended categorisations will be put forward to IUCN.

    The final Red List categories will be published on the BirdLife and IUCN websites in mid-2014, following further checking of information relevant to the assessments by both BirdLife and IUCN.

  3. Mark Pearman says:

    The distributional and even altitudinal data used, in part, to define species and threat status is just way off the mark. Jaramillo (2003) mentions and maps widely allopatric tarapacensis from pennata (i.e. extreme northern and southern Chile e.g. 5000 km apart) with the mention of vicariant events that separated them possibly including the rise of the Andes. Jaramillo (presumably influencing Birdlife) completely overlooked the situation in Argentina where both taxa are either parapatric or grade into one another in Mendoza province, central Argentina. There is NO major break at all in the distribution from the Bolivian-Argentine border to extreme southern Santa Cruz and southern Chile. In addition to Jujuy, Salta and Catamarca provinces, tarapacensis also occurs in La Rioja, San Juan and Mendoza provinces (USNM specimens), whereas pennata ranges from Mendoza southwards. In La Rioja it frequents the monte desert ecosystem unique to Argentina and reaches 1220 m. , i.e. very much lower than the quoted 3,500 m. Furthermore, tarapacensis is found in at least 10 Argentine AICA’s (published by birdlife Argentina) and at least three national parks. Even looking at Birdlife’s statement … ”’R. pennata is found in…. southern Argentina” makes me wonder if this article and future decision making was researched at all. Mendoza lies at the same latitude as Buenos Aires in central Argentina, and that is at least 1300 km. north. Although tarapacensis could be declining it’s primary habitat is in truly vast uninhabited areas. “Populations of all forms in the R. pennata complex have declined markedly in recent decades” is just another unsubstantiated and if anything erroneous statement when concerning nominate pennata. In sum, after reading through multiple erroneous statements presented by BirdLife, and lacking any serious paper on splitting these taxa in the first place, I would say that BL need to properly research the facts before making any future suggestions regarding this species.

  4. Mark could very well be correct. But we are still no closer to figuring out the question of one or two species here. He mentions that both taxa are “either parapatric or grade into each other” but it would be vital to know which one of these it is. Are they parapatric, with a small intervening area of hybridization? Are they clinal over a large area? Are they separated by a narrow but significant area of habitat or elevation? Do they overlap and not interbreed? Mark clarifies that the situation may be much easier to figure out given that there is the potential for overlap or near overlap, but still the data is not available to say one way or the other.
    These birds are difficult as they do not have showy plumages we can compare, vocal data we can look at. They are also flightless, so even a narrow area of unsuitable habitat could be as great a barrier as a mountain range for these birds. It may take genetic work to determine if there is gene flow between populations and if there has been a long period of isolation or not?
    Either way, the population estimates appear low to me for tarapacensis. Also we have no concrete surveys to work from to assess population numbers and trends at least in Chile. But on birding tours I have seen that this form is either stable or increasing in Lauca National Park, my gut feel is that they are increasing. This is also not the only place it is found in Chile, the Peruvian border to the highlands of Antofagasta is quite a distance. Surely there are at least many hundreds there, but I would be foolish to give a number given how little some of these areas are searched.

  5. Mark Pearman says:

    Exactly Alvaro, so many different scenarios yet some here want to believe that two species are involved without seeing the evidence. How can we even debate whether another species is involved when there are no published studies? If a ball goes over the goal line in football, it’s a goal, but if it’s still touching the line it shouldn’t be allowed. In the case of Lesser Rhea, we can’t even see the line, because it’s under muddy water.

  6. Andy Symes says:

    We appreciate these comments and information regarding the validity of this taxonmic change, however the taxonomy to be followed in 2014 has been finalised and so there will be no change to the planned split of Rhea pennata this year. There will however be an ongoing opportunity to review the BirdLife/Lynx Taxonomic Checklist as and when new information becomes available, and so whilst we do not envisage a significant number of reversals of changes adopted in 2014, it should be noted that these are not necessarily set in stone.

    Recommended categorisations to be put forward to IUCN

    Based on available information and comments posted above, our recommended categorisations to be put forward to IUCN for the 2014 Red List are:

    R. pennata as Least Concern

    R. tarapacensis as Near Threatened, suspected to approach the thresholds for classification as Vulnerable under criterion A2ad – change to the preliminary proposal.

    The final Red List categories will be published on the BirdLife and IUCN websites in mid-2014, following further checking of information relevant to the assessments by both BirdLife and IUCN.

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