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 soon publish the HBW-BirdLife Illustrated Checklist of the Birds of the World, 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 2013 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.

References:

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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