This highland EBA extends from the Chisos mountains of southern Texas in USA, south-eastwards along the north-east edge of the arid central-northern Mexican plateau in Coahuila state to the northern part of the Sierra Madre Oriental in Nuevo León and Tamaulipas states. To the east lies the extensive coastal plain of the North-east Mexican Gulf slope (EBA 011), while the southern end of the EBA marks the beginning of the Southern Sierra Madre Oriental (EBA 012).

The lowest altitude of the Sierra Madre Oriental EBA marks the upper limit of desert scrub, which predominates on the Mexican plateau to the west. The main vegetation types in the EBA between 1,800 and 2,500 m are oak scrub, pine Yuccajuniper scrub, or pine oak Arbutus forest, and above this altitude coniferous forest with firs Abies and several Pinus species. In degraded areas, scrub (chapparal) is the main habitat covering the slopes.

The EBAs two restricted-range species overlap in the northern part of the Sierra Madre Oriental, which encompasses the entire range of Rhynchopsitta terrisi. The breeding range of Vermivora crissalis extends the EBA further north. Lanning et al. (1990) showed that V. crissalis was present in most areas of open pine oak forest where the average height of the trees reached 8 m and where there was a good understorey of shrubs and ground vegetation. The species winters out of the EBA principally in oak conifer forests of central Mexico (EBA 012) and humid to semi-humid montane forests of the Pacific slope of western Mexico (EBAs 005, 006) (Lanning et al. 1990, Howell and Webb 1995a).

The prime habitat of Rhynchopsitta terrisi is mixed conifer forest, mostly at higher elevations although, interestingly, the species nests exclusively in holes in limestone cliffs, there being few trees of sufficient size to offer nest-holes.

The mixed-conifer forests of this EBA are being destroyed by fire, logging and clearance for agriculture. This habitat destruction is the reason for Rhynchopsitta terrisi, which has a relatively circumscribed range, being judged to be threatened. The largest single observation since 1978, and perhaps ever, was made in October 1994 when 1,480 birds were seen (E. Enkerlin in litt. 1995). A significant portion of the southern half of this EBA, and indeed the range of R. terrisi, is covered by the Cumbres de Monterrey National Park (2,465 km²), which embraces the highland pine forests near Monterrey City. The national park is one of the largest designated protected areas in Mexico, but unfortunately is poorly administered. A working group is investigating how to give effective protection to the park, and an initial proposal includes reducing its size to c.1,500 km² in order to focus on the area of highest conservation value (E. Enkerlin in litt. 1995). Another promising conservation initiative for the parrot is the creation of the El Taray Sanctuary (3.6 km²) to protect the largest-known nesting cliff of the species holding c.100 pairs which is roughly a quarter of the total breeding population currently known (Snyder and Enkerlin 1996, World Birdwatch 1996, 18: 4).

The northern part of the EBA from the Chisos mountains to western Coahuila state encompasses the southern end of the breeding range of Black-capped Vireo Vireo atricapillus (classified as Endangered). This species has suffered a substantial contraction of its US breeding range owing to habitat loss and near-total nest-parasitism by Brown-headed Cowbird Molothrus ater, although numbers in Coahuila (in this EBA) remain disputed (Collar et al. 1992, Collar et al. 1994).

Recommended citation
BirdLife International (2024) Endemic Bird Area factsheet: Northern Sierra Madre Oriental. Downloaded from https://datazone.birdlife.org/eba/factsheet/6 on 23/11/2024.