The Sierra Los Tuxtlas are mountains located near the coast of the Gulf of Mexico in the Mexican state of Veracruz. It is an area of intense volcanic activity with many peaks, including Volcán San Martín Tuxtla at 1,700 m and Volcán Santa Marta at 1,650 m (Dirzo and García 1992). From Sierra Los Tuxtlas, the EBA probably spreads south-east into the Gulf slope of the Isthmus of Tehuantepec in the Uxpanapa region of extreme eastern Veracruz and eastern Oaxaca, and in the El Ocote region of western Chiapas.

The principal habitat of the EBA is tropical rain forest, which is at its northern limits for eastern Mexico. The forest can be divided into lower montane and montane types, especially on the slopes of Volcán San Martín Tuxtla and Volcán Santa Marta (Andrle 1967). In the lowlands of Uxpanapa and El Ocote there are distinct zones of tropical rain forest found on limestone karst, a prominent characteristic of these areas being large rocky outcrops in otherwise flat terrain. The EBA encompasses two areas (notably the Uxpanapa region) of the three in eastern Mexico which receive unusually high rainfall and which have pronounced levels of plant endemism and species diversity (Wendt 1993, WWF/IUCN 1997).

This region has been identified as an EBA since the previous analysis (ICBP 1992) owing to the recent recognition of Geotrygon carrikeri and Hylorchilus navai as full species. G. carrikeri was previously regarded as a well-marked and isolated subspecies of the widespread Purplish-backed Quail-dove G. lawrenci of Costa Rica and Panama, but its larger size, paler plumage and possibly different calls and egg colour, as well as the fact that its breeding range lies more than 1,500 km from that of the nominate form, together indicate that it is better treated as a species (Peterson 1993, Howell and Webb 1995a). It is confined to the Los Tuxtlas region, occurring on both of the main volcanoes. H. navai was originally described as a subspecies of Sumichrasts Wren H. sumichrasti (see Atkinson et al. 1993 and Secondary Area s006). It was poorly known until the 1980s when populations were found in the northern part of the Uxpanapa region, mainly in the Coatzacoalcos drainage of eastern Veracruz, in neighbouring Oaxaca and in western Chiapas along the La Venta canyon (Collar et al. 1992, Whittingham and Atkinson 1996). Its range lies within the forests on karst limestone outcrops in the central zone of the Isthmus of Tehuantepec.

Campylopterus excellens is probably found throughout the EBA (i.e. in the intervening lowland area between Sierra Los Tuxtlas and the Uxpanapa and El Ocote regions), but most records are from the Sierra Los Tuxtlas with a few in the Uxpanapa region and just one from western Chiapas in the El Ocote region (Howell and Webb 1995a). The bird is, however, very similar to the widespread Wedge-tailed Sabrewing C. curvipennis (with which it is often considered conspecific), and so may well be overlooked. In Sierra Los Tuxtlas it is a fairly common member of the understorey avifauna, also occurring there in degraded habitats such as forest edge and overgrown orchards (Winker et al. 1992).

The EBA has suffered from extensive deforestation especially in Veracruz. A recent study estimated that 86% of the original forest area of Volcán San Martín in the Sierra Los Tuxtlas had been lost by 1986 (Dirzo and García 1992). Flatter areas on the karst limestone areas are being cleared, mainly for cattle-grazing and agriculture, leaving isolated forest fragments on the main rock outcrops. Much forest within the immediate range of Hylorchilus navai has presumably been destroyed by the creation of a reservoir, Lake Malpaso, in western Chiapas. Both Geotrygon carrikeri and H. navai are considered threatened owing to the large-scale habitat destruction in the region.

In spite of the serious habitat loss which has occurred within the EBA there do exist a number of protected areas which give some security to the regions remaining forests, including Santa Marta Biosphere Reserve (546 km²) and Los Tuxtlas Biological Station (6 km²), the latter the best-studied forest site in Mexico (Dirzo and García 1992). Additionally, La Venta river in western Chiapas, where Hylorchilus navai has been recorded, lies within the El Ocote Ecological Reserve (c.480 km²). In the Uxpanapa area, the Los Chimalapas–Uxpanapa Biosphere Reserve has been proposed (8,000 km²), covering a relatively undisturbed transect through lowland rain forest in Uxpanapa to extensive montane forest in the Chimalapas mountains to the south (Wendt 1993).

Recommended citation
BirdLife International (2024) Endemic Bird Area factsheet: Los Tuxtlas and Uxpanapa. Downloaded from https://datazone.birdlife.org/eba/factsheet/30 on 23/11/2024.