This EBA follows the course of the upper Orinoco (south of Puerto Ayacucho) and its tributaries such as the Ventuari (Amazonas state, southern Venezuela) and Vichada (Vichada department, eastern Colombia), and also the upper Río Negro watershed including the Casiquiare (in Amazonas department, Venezuela), the Guainía, Tomo and Vaupés (in Guainía, Guaviare and Vaupés departments, south-east Colombia), and the Cauaburi, Xie, Içana, Uaupés and Curicuriari (mostly west of Uaupés, in northern Amazonas state, Brazil).

The EBA is cloaked in (mostly undisturbed) primary lowland humid forest up to c.500 m, although along many of the rivers (especially the upper Orinoco watershed) this is more specifically described as riverine white-sand forest. There are numerous small patches and pockets of rocky (partially deciduous) vegetation and savanna (Huber and Alarcón 1988) similar to 'campina' and 'caatinga'; partially inundated 'igapó' forest is also present along some of the rivers. The low sandstone serranías of south-east Colombia are also included.

Most of the birds appear confined to or associated with the relatively specialized humid lowland forest growing on the white-sand soils, but some species are also found in more open woodland, forest-edge and savanna situations. These vegetation types, and thus the birds, seem to be restricted to the lowlands and low serranías below 500 m.

The species in this EBA are all relatively poorly known (most being recorded from less than 10 localities), with (apparenty) large gaps in their distributions. Recent surveys in east and south-east Colombia (Serranía de Naquen in southern Guainía and Serranía de Teraira in southern Vaupés) have extended the known ranges of many of the endemic birds (Anon. 1992a, A. Payne in litt. 1995), but further work is needed to determine precise ecological requirements in order to be able to predict more precisely what their distributions are likely to be.

Thripophaga cherriei is known from just seven specimens taken in 1899 and 1970 along a single affluent (the Capuana river) of the upper Orinoco in Venezuela (Collar et al. 1992), but, with further searching, it is likely to be found along other rivers and across the border in Colombia. In Colombia, outside the immediate area of the EBA as defined above, Crypturellus duidae has been found in the Serranía de la Macarena in Meta department (Secondary Area s019), and is predicted to occur on the table mountains in Vaupés department (Hilty and Brown 1986). In Venezuela, Herpsilochmus dorsimaculatus is found in the lowlands around the Tepuis (EBA 064), although it does not seem to be directly associated with them and so is considered confined to the present EBA.

This EBA is relatively unaffected by human activities, due primarily to the low human population density and the difficulty of access. However, the extraction of white-sand silica, the expansion of gold mining and frequent burning pose major threats to some portions of the EBA, with clearance for cattle-grazing also having an impact (Dinerstein . 1995, A. Grajal in litt. 1993).

Only Thripophaga cherriei is presently thought to be threatened, although this is due mainly to the paucity of records (see 'Restricted-range species', above) rather than any immediate or perceived threat from habitat destruction (Collar et al. 1992, 1994). The only known locality for this species was identified as a Key Area for threatened birds in Wege and Long (1995).

The vast Alto Orinoco–Casiquiare Biosphere Reserve (840,000 km²) presumably provides some formal protection to the EBA in southern Venezuela, as do a number of indigenous reserves (e.g. Alto Río Guainía, Bajo Río Guainía y Río Negro, and Cuiari-Isana) in south-east Colombia, and the Rio Negro Forest Reserve and indigenous areas (e.g. Içana-Ajari and Içana-Xie) in north-west Brazil (IUCN 1992a). The extent to which any of these reserves provides adequate, on-the-ground protection is unknown. The whole of Amazonas state in Venezuela is legally protected from mining and forestry by governmental decree, although a proposal has recently been tabled to revoke the relevant decrees in order to legalize these activities within the state (C. J. Sharpe in litt. 1996). Irrespective of the decrees, all protected areas within Amazonas state are currently affected by gold- and diamond-mining (C. J. Sharpe in litt. 1997).

Recommended citation
BirdLife International (2024) Endemic Bird Area factsheet: Orinoco-Negro white-sand forest. Downloaded from https://datazone.birdlife.org/eba/factsheet/39 on 22/11/2024.