Special Conservation Report: Ecological Aspects of the Yucatan Parrots & Perspectives for Their Conservation

Abstract

During the three month period from April to June 1989, nine journeys were made around the Yucatan Peninsula. These took in extensive portions of Yucatan, Campeche and Quintana Roo, and covered some 4, 200 kilometers of highways and white roads (see map).

In the state of Yucatan, coastal regions were visited at Sta. Maria de Sisal in the west and at Rio Lagartos, San Felipe and El Cuyo in the east. To the south was included the mechanized agricultural and horticultural region between Oxcutzcab and Tekax, taking in the most distant portions such as the villages of Tigre Grande, Becanchen, Nohalal and Hunto Chae. This region represents an area of some 40,000 ha. enclosed by four perimeter roads.

In the state of Campeche, parts of the Calakmul Biosphere Reserve were visited and also the neighboring "ejido" of Alvaro Obregon at the northeastern boundary. Here, visits were made from the 24th through the 28th of April and from the 25th through the 27th of June.

Only one extensive journey was made to the state of Quintana Roo and this was affected by strong transient rains.

Our aim is to gain detailed knowledge of the seasonal food habits and local movements of the parrots and to diagnose the current state and distribution of their populations, as well as the plant associations which still remain as natural habitat in the south of the Yucatan.

The passage of Hurricane Gilbert in 1988 obliged thousands of parrots to invade the citrus groves in the south of the state of Yucatan. A battle ensued in which the horticulturists used mainly firearms against the birds. The future consequences of the latter event, along with our lack of knowledge of current population levels of the parrots in the area (although it is thought they have suffered a drastic reduction in numbers in recent years), were among the central motives for carrying out this report.

To obtain data, interviews were carried out with local inhabitants with emphasis being placed on aspects of capture, trade, human disturbance, nesting areas and the birds' food. During field work, we proceeded to determine those plants with flowers or fruits and collected material for a herbarium. In addition, some markets were visited in the main towns in the south of the Yucatan.

 Summary of Progress Made

1. Field Surveys

Visual surveys showed that the large groups of parrots consisting of hundreds of individuals reported at the end of 1988, specifically in the horticultural zone of the Yucatan, were no longer present in the area. Apparently, no large concentrations were to be seen from March onwards 0. Ehrenberg, pers. comm.). The extensive surveys carried out between April and June 1989 in numerous localities of the Peninsula were characterized by the absence of such gatherings.

Observations took place in April and June. In May, surveys of the littoral zone of the Yucatan yielded no records of parrots. Most observations were during the early hours of the morning and at dusk (Table 1 ), the majority of these being of pairs or singles. The total number of parrots seen was 216 (Table 2).

Groups, when seen, were of small size, the largest being of 16 birds seen flying in pairs. Groups of parrots seen flying in the south of Campeche during the last days of June were more or less defined due to the fact that it could be clearly seen that they were moving in pairs. This is in contrast to what was observed at the beginning of April when the few groups that were seen were flying in aggregations with no apparent order. The latter phenomenon was again observed in early July by Rafael Castillo.

In total, 19 days were spent in the field. Of these, parrots were recorded on 13 days so that the frequency of occurrence (68.4%) was high. The frequency of occurrence was obtained following Edwards and Tahsian (cited in Nocedal, 1981), where it is described as the quotient of the number of days with records by the total number worked, multiplied by 100.

2. Food

A list was made of some of the plant species utilized by the parrots, whether this be as a food source or as nest sites. At present, direct evidence is scant and the results of interviews with the local inhabitants revealed 19 species of trees altogether, several of which are considered of use to the human population (see list).

Table 3 presents the phenology of some trees that are important in the parrots' diet. This is related to the time of year when citrus fruits are harvested in the Yucatan. The phenological data have been taken from biogeographical sources. However, specific information for the area, which is deposited in the herbarium of the Centro de Investigaciones Cientificas de Yucatan (CICY), is in the initial stages of being collected.

3. Reproduction

These species form pairs in late March and during the first weeks of April, and, for this reason, it is at this time that flocks break up and disperse. In May, the first chicks, normally two per brood, begin to hatch. However, some of those interthis was backed by direct observational evidence. These trees are the "Chaca" 'Bursera simaruba) and the "Kitmiche " (Caesalpinia gaumeri). The first has a soft wood which is easily worked with the bill. The second is a leguminous species of hard wood but which has an irregular body structure that commonly gives rise to many natural hollows. Both species are abundant in the south of Yucatan and the "Chaca " has a high potential for regeneration and growth, as well as being a species which is dispersed by birds (Sousa, 1969).

Some species of palm are also used as nest sites by parrots. Species of "Guano" (Sabal yapa), whose leaves are esteemed by regional inhabitants for the construction of the thatched roofs of traditional dwellings, have a wide distribution and important populations on the peninsula. Coconuts (Cocus nucifera), which are intensively cultivated along the coasts, are also appreciated by the rural population of the interior. There appears to be an important nesting area in the coconut groves of Caba Catoche, Quintana Roo.

Other sites used frequently are termite nests and preferably those constructed in the crowns of trees. A pair of Aratinga astec was in occupation of one of these constructions in the south of Campeche in April.

No evidence is available concerning the segregation of A. xanthora and A. albifrons for breeding, either in regard to area or different plant associations. A campesino from the south of Quintana Roo can find a nest of either of the two species, as was observed on a ranch to the south of Felipe Carillo Puerto. However, we are told that A. xantholora is ' 'scarcer: '