Táchira Antpitta Grallaria chthonia on the EDGE: evolutionarily distinct and globally endangered

Táchira Antpitta Grallaria chthonia (Mercedes Madriz)

Last week, a team of UK and US scientists published a paper identifying the conservation priorities for the world's 9,993 bird species based on evolutionary distinctness, a measure of a species’ contribution to the total evolutionary history of its clade[...], expected to capture uniquely divergent genomes and functions (Jetz et al. 2014). In parallel, the Zoological Society of London compiled a list of the world's 100 most Evolutionarily Distinct and Globally Endangered (EDGE) bird species. The findings were widely publicised by the media.

The ZSL's EDGE list includes one Venezuelan bird, Táchira Antpitta Grallaria chthonia, ranked 89th. This Venezuelan endemic is one of the very few of the world's birds that remain unknown in life: there are no photographs, no sound recordings and no living person has ever encountered one. The species is only known from four specimens collected at a single locality nearly 60 years ago. In short, it is an avian enigma. Its curious specific epithet derives from the Greek khthonios, meaning "in the earth" – and it might as well be.

The only evidence that the bird really exists are the four museum specimens languishing in the drawers of the Colección Ornitológica Phelps in Caracas and the Smithsonian Institution in Washington DC. All of them were obtained from the same tiny spot: Hacienda La Providencia (c.7°38'N 72°15'W; Paynter 1982), along the río Chiquito in southwestern Táchira state, on the eastern slopes of the Páramo de Tamá in the Andes of western Venezuela. The holotype (COP 61.055, on deposit at USNM, now NMNH) was taken at 1,800 m by the Phelps Collection's intrepid collector Ramón Urbano on 10 February 1955, together with a paratype. Two further skins – both males like the previous type specimens – were obtained at 2,100 m the following March and the species was described later that year by Wetmore and Phelps (1956). The female has never been encountered.

That is the last time that the bird was seen in life. A three-day search specifically for the species in September 1990 was unsuccessful, but there was no reason to fear for its future, since the type locality still held pristine forest above 1600 m (Collar et al. 1992). By December 1996 however, coffee plantations in the río Chiquito Valley had advanced up to 1600 m, and much forest at 1900–2200 m (including the type locality) had been converted to agriculture; although the species was not found at this time, it may have been present in neighbouring valleys, which were apparently less disturbed (BirdLife International 2000).

The type locality for Grallaria chthonia and the forests that surround it lie within Venezuela's El Tamá National Park, an IUCN Category II protected area which extends over 1,390 km² and is designated as an Important Bird Area (Lentino & Esclasans 2005), part of the Colombian East Andes Endemic Bird Area. In addition, the known and potential range falls within one of the highest priority bioregions for the conservation of Venezuela's birds (Rodríguez et al. 2004). This region is also recognised as one of the most threatened in Venezuela, with at least 17% of the habitat within the National Park affected by deforestation for agriculture (principally coffee cultivation) and to create livestock pasture (Sharpe & Lentino 2008).

For the above reasons, Táchira Antpitta is considered Critically Endangered both nationally and internationally (Sharpe 2008, BirdLife International 2014). Its population is now estimated to consist of fewer than 50 mature individuals (BirdLife International 2014).

Basic field surveys are urgently needed in order to determine the true status of this virtually unknown antpitta; seasonality of vocalisation should be taken into account, with surveys to be carried out in May–June (BirdLife International 2014). In addition, there are questions over its true taxonomic status. On plumage characters, Grallaria chthonia appears to be most closely related to G. guatimalensis and Hilty (2003) suggests that it may be a higher elevation subspecies of the latter. On the other hand, Ridgely & Tudor (1994) and Krabbe & Schulenberg (2003) believe that chthonia is probably more more similar to (or even conspecific with) alleni. Until the species is better known, with molecular and vocal evidence considered, the true affinities of this evolutionarily distinct and globally endangered species will remain uncertain. 

Further information on this species – and all the world's birds – can be found at HBW Alive.


References

BirdLife International (2000) Threatened birds of the world. Lynx Edicions & BirdLife International: Barcelona & Cambridge. 852 pp.

BirdLife International (2014) Species factsheet: Grallaria chthonia. Downloaded from http://www.birdlife.org on 17/04/2014.

Collar, N.J., Gonzaga, L.P., Krabbe, N., Madroño, A., Naranjo, L.G., Parker, T.A. & Wege, D.C. (1992) Threatened birds of the Americas. The ICBP/IUCN Red Data Book. 3rd edition, part 2. ICBP: Cambridge. 1,150 pp.

Hilty, S. L. (2003) Birds of Venezuela. Princeton University Press: Princeton NJ. 928 pp.

Jetz, W., Thomas, G.H., Joy, J.B., Redding, D.W., Hartmann, K., Mooers, A.O. (2014) Global distribution and conservation of evolutionary distinctness in birds. Current Biology. 

Krabbe, N.K. & Schulenberg, T.S. (2003) Family Formicariidae (ground-antbirds). Pp. 682-731 in del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.) Handbook of the birds of the world. Volume 8. Lynx Edicions: Barcelona. 845 pp.

Krabbe, N.K., Schulenberg, T.S. & Sharpe, C.J. (2013) Tachira Antpitta (Grallaria chthonia). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.) Handbook of the birds of the world alive. Lynx Edicions: Barcelona. Retrieved from http://www.hbw.com/node/56887 on 17 April 2014.

Lentino, M. & Esclasans, D. (2005) Áreas importantes para la conservación de las aves en Venezuela. Pp. 621-769 in: BirdLife International and Conservation International (eds.) Áreas importantes para la conservación de las aves en los Andes Tropicales (Serie de Conservación de BirdLife, No. 14). BirdLife International: Quito, Ecuador.

Paynter, R.A. (1982) Ornithological gazetteer of Venezuela. Harvard University, Museum of Comparative Zoology: Cambridge, Mass. 245 pp.

Ridgely, R.S. & Tudor, G. (1994)  The birds of South America. Volume II: the suboscine passerines. University of Texas Press: Austin. 814pp.

Rodríguez, J.P., Rojas-Suárez, F. & Sharpe, C.J. (2004) Setting priorities for the conservation of Venezuela's threatened birds. Oryx 38(4): 373-382.

Sharpe, C.J. (2008) Aves. Pp. 116-157 in: Rodríguez, J.P. & Rojas-Suárez, F. eds. Libro Rojo de la fauna venezolana, 3rd edition. Provita & Shell Venezuela, S.A., Caracas, Venezuela. 364 pp. 

Sharpe, C.J. & Lentino, M. (2008) Hormiguero tororoi tachirense Grallaria chthonia. P. 144 in: Rodríguez, J.P. & Rojas-Suárez, F. eds. Libro Rojo de la fauna venezolana, 3rd edition. Provita & Shell Venezuela, S.A., Caracas, Venezuela. Available online as: Sharpe, C.J. & Lentino, M. (2013) Hormiguero tororoi tachirense Grallaria chthonia. WikiEVA: Especies Venezolanas Amenazadas.

Wetmore, A. & Phelps, W.H. (1956) Further additions to the list of birds of Venezuela. Proceedings of the Biological Society of Washington 69: 1-10.

Recommended citation:-

Sharpe, C.J. (2014) Táchira Antpitta Grallaria chthonia on the EDGE: evolutionarily distinct and globally endangered. The Curious Naturalist. Downloaded from http://thecuriousnaturalist.blogspot.com/2014/04/tachira-antpitta-grallaria-chthonia-on.html on .