Although not the largest and deepest of the area's sinkholes, it is best known because of a tourism project which focuses on the thousands of Mexican green parakeets who live there most of the year, flying in and out in circular patterns.

[6] The climate of the area is mostly warm and humid, with a rainy season from June to October, receiving an average of 1,500mm of precipitation per year.

[7] The Sima de las Cotorras belongs to a Karst topography system, based on the folding, fracturing and erosion of limestone.

The two processes have created a number of formations including canyons, arches, caves, waterfalls, small pools of water and sinkholes.

[7] Major formations include the La Venta River Canyon, the Arch of Time (Arco del Tiempo) and El Aguacero Falls.

[6][7] These sinkholes are vertical depressions formed by the cracking, erosion and collapse of limestone over thousands of years.

[3] El Ocote is home to a number of endangered species, especially birds such as Psittacara holochlorus, Amazilia viridifons and Oporornis tolmiei, as well as other receiving special protection such as Eucometis penicillata, Lanio aurantius, Psarocolius montezuma and Colinus virginianus.

[7] From its bottom grows a tropical deciduous rainforest microsystem with broadleafed species such as cedar, mahogany, Fabaceas espinosa and Burseraceas baja, Manilkara zapota, scrubs of the family Guaiacum and more, with trees reaching as high as 30 meters tall.

[8] Common reserve fauna includes owls, foxes and coyotes, rabbits, opossums, badgers, squirrels, armadillos, Penelopina nigra, chachalacas and of course, parakeets.

These include species which are highly sensitive to human intrusion such as Colinus virginianus, Caprimulgus vociferous, Amazilia candida and Ortalis vetula.

A number of bird species have been found in the Sima de las Cotorras area but not in the larger El Ocote park, including Bubo virginianus, Ramosomyia viridifrons, Vireo philadelphicus, Sialia sialis, Passerina versicolor and Cacicus melanicterus.

And many of Mexico's parrot species are endangered, mostly due to shrinking habitat, along with the illegal pet trade and other exploitation of the animals.

[1] The parrots leave the sinkhole to look for food, which includes from mango trees in people's backyards as far away as Tuxtla Gutierrez.

[6] The area of the park was first explored and academically documented in the mid 20th century, noting local caves and archeological finds such as pottery.

[6] The significant archeological find in and around the Sima de las Cotorras are cave paintings, arrowheads, and much later pottery shards, possibly Zoque.

[3][12] The appearance of cave painting in such a geological formation and especially so high up the sinkhole walls makes them a rarity, and the site is under consideration by UNESCO for protective status.

[7] The El Ocote Biosphere Reserve was established in 1972, extendingover 8 hectares, protecting over a hundred species of birds, and dozens of mammals, reptiles and insects, some endangered.

[10][13] With the exception of the Sima de la Cotorras, the park has not been developed for tourism, and its formations are almost completely unknown outside of their region.

[6][7] Tourism activity here began with the establishment of the Sima de Cotorras Ecotourism Center in 1985 and the building of a road from the town of Ocozocoautla to the site.

[2][6] The project is also registered with the federal government as an ecotourism site, with the aim of being sustainable, providing income for local residents with minimal impact.

[7] By far the main attraction of the site are the parrots that fly in and out of sinkhole each day, generally leaving in the early morning and returning at night.

[2] The project over the years has received intermittent support from various government institutions such as PEMEX, the Secretary of Tourism, SEMARNAT and the Comision Nacional para el Desarrollo de los Pueblos Indígenas, in areas such as finance, customer service and construction.

[2] Changes in political parties has led to varying attitudes towards the project and its ecological focus, with errors being made such as cutting down trees to make way for cement electrical poles and the construction on non-composting toilets.