Abstract
Two hundred miles south of the Texas-Mexico border a dramatic transformation occurs. Arid mesquite woodlands and sorghum fields adjoin tropical rivers and lakeshores. Supporting a variety of plants many of which produce edible fruits or seed pods, the scene is set for the Amazon parrot.
The yellow-crowned Amazon (Amazona ocbrocepbala) is the first species encountered. In the northern portions of its range it shares the arid tropical lowlands and riverine forest with the smaller green-cheeked Amazon (Amazona viridigenalis). Proceeding southward, the yellowcrowned Amazon continues to be observed, in one subspecies form or another, into South America. The range of the green-cheek, however, is much more restricted extending only into the Mexican state of Veracruz. With the encroachment of tropical, decidious forest, the green-cheek is replaced by the more forest-loving yellow-cheeked Amazon (Amazona autumnalis). Westwardly the green-cheek can be observed well into the pine-oak belt of the Sierra Madre Oriental range.
Due to its restricted range and popularity in the pet trade, I began a field study in 1983 inquiring as to the status of the species in the wild. Funded, in part, from A.F.A. Avian Research Grants in 1982-83, this paper summarizes my findings during the preliminary trips into the species' range in 1983. A subsequent paper will deal with the species' diet and conservation. ''A great flock of red-crowned parrots flies swiftly down river. Some of them are very low, only a few yards above the house. Heelo, heelo, heelo, era, era, era they shriek, the sound is deafening.'' Cornell-Clarkton Expedition of 1941 in: At A Bend In A Mexican River,
Sutton, 1972.
Mexico has changed a great deal since the early travels of George Sutton. The mighty El Salta Falls has since been tamed by a hydroelectric facility, the magnificent ornate hawk-eagle is seldom seen and the shrieking cry of the green-cheeked parrot can hardly be ''taken for granted as the air we breathe.'' Throughout 1983 I made seven trips into the range of the species. Trips were made in the months of January, February, June and August. With the aid of a LANDSAT satellite photograph, I attempted to visit all areas of undisturbed forest accessible by a fourwheel drive vehicle. Residents were frequently questioned as to the abundance of the species. Captive birds were investigated as to their origin.
DESCRIPTION
Since most individuals are familiar with this species, only a brief description will be given. In general, the species is approximately 12 inches in length and green in coloration. The forehead, lores and crown are crimson to varying degrees. As with the other members of the genus Amazona, the base of the outer webs of the first five secondaries have red markings. In the field its call, a distinctive era, era, era, is unmistakable and often the only means of identifying young birds in flight. Several authors have mentioned that the amount of crimson is greater on the males. Not having examined a large number of birds of known sex and noting several examples that did not conform to this statement, I can't support its validity.
RESULTS
As stated previously, the greencheeked Amazon is first encountered approximately two hundred miles south of Brownsville, Texas. One of the first areas where the species' presence has been documented is along the Rio Corona, one of several rivers that feed into the popular bass fishing lake Vicente Guerrero. During a camping trip in 1978, the species, although not abundant, was present along the riverine forest in small numbers (5-15 birds). Within recent years, however, extensive clearing of the vegetation along the river combined with the accelerated popularity of the area for bathing, washing and swimming purposes has had a dramatic, negative effect upon the parrot population. In addition to the Rio Corona, parrots are also present along the lake itself. Other rivers flowing into the lake (e.g., Rio Purificacion, Rio Soto la Marina) support additional populations of A. viridigenalis although, like the corona, the numbers are low and on the decline.
Proceeding south from the lake through the city of Ciudad Victoria the arid slopes of the Sierra Madre Oriental are soon within view. Without the moisture provided from rivers and streams, only sparse dwarf oaks and thorny scrubs exist. From this point south the habitat vegetation takes a tropical "twist." The major section of such is found along the Rio Sabinas in what is frequently called the Rio Sabinas river valley. Approximately 100 miles south of Ciudad Victoria a great deal of the area is in a ''more or less" natural state providing feeding, roosting and the nesting requirements for the green-cheeked Amazon.