Abstract
The Yellow-naped Amazon (Amazona auropalliata), is one of the most popular psittacines in aviculture today, and like most psittacines in captivity little is known of its ecology. We know that they do well in a captive environment and much has been done to improve diets there and give them all that is necessary for their reproductive success. But what do we really know of their actual needs?
Since 1985, and more intensively in the last six months, I have spent my time studying this question. I have observed the Yellow-naped Amazon (A. auropalliata) on the south coast of Guatemala, particularly in the area of Santa Rosa, where the populations which still exist in the wild are concentrated. Here, 30 miles from the El Salvadoran border, where the land has been heavily disturbed and deforested (principally for large cattle and sugar cane ventures), where heavy use of pesticides is common, and where habitat is further denuded by the locals cutting firewood, trapping wildlife and planting their subsistence plots of com, the Yellow-naped Amazon exists in the small ecological niche left to it.
In studying the diet of the Yellownaped Amazon during its breeding season (roughly, December through April), I began by locating private Fincas (large private land holdings) with active nests then in use by Yellow-naped Amazons. I succeeded in locating six active nests, and secured permission to observe four. By studying these nesting pairs and following these birds on their daily flights to feeding areas, by observing non-nesting Yellow-naped Amazons in other feeding and roosting areas, by examining the crop contents of the chicks in the nest, and by conducting local interviews, I have identified 22 species of trees used by Y ellow-naped Amazons as a food source during their breeding season.
The following list sets forth those 22 trees by local common name, what part of the seed or fruit is consumed and at what stage of the seed or fruit's development and, where data is available, a breakdown of water/ protein/ carbohydrate/ fat/ eel- 1 ulose content for each source. To the extent other psittacine species feed from the same food source, I note same. Finally, the list sets forth trees by relative popularity in the Y ellow-naped Amazon's diet.
I consider the list to be complete for the dry/breeding season (November through April) and for the study area. Many of these trees fruit more than once a year, i.e. Sterculia apetala will fruit up to three times a year giving the Yellow-naped Amazon a certain consistency in its diet throughout the year. There are undoubtedly other foods utilized during the non-breeding (rainy) season.
Moreover, the rainy season is the time when agriculture is at its peak and the Yellow-naped Amazon has been observed flying down to corn fields (Milpas) therefore being more of a pest and more dependent of agricultural crops than in the dry/breeding season.
One interesting conclusion I came upon was the decided preference for four of these trees, the Castano, Maranon, Ceiba and the Conacaste tree. They form the vast bulk of the Yellow-napedAmazon's diet- a general impression confirmed by examination of the crops of the chicks (at roughly four weeks of age) in the nest. Other sources, such as (Bursera simaruba), were of far lesser importance and were utilized only sporadically or as alternatives when its preferred rood source was not in the vicinity of the nest. Why the concentration of these four trees when other foods were available in the area? Perhaps the answer lies in the common attributes of these four trees: high protein and fat content and low water content.
Does it not make sense that Yellownaped Amazons at nesting time will concentrate on high fat, cost-efficient foods for the rapid development of chicks? Might the needs of parenting chicks also explain the avoidance of fruit intake? For example, the fruit of Anacardium occidentale (cashew fruit) was abundant at this time but was never consumed (the parents eating the nut only). Thus the hypothesis is that parents want a low water intake. Moreover the Yellowna ped Amazon was never observed by myself or by the natives to drink water. This may be due to the fact that they want to decrease the water intake in the nest cavity. Similarly, this and other fruits give comparatively less food value for the development of chicks and would be digested far quicker than the thick pulp of the preferred foods. In other words, the preferred foods permit the parents to visit the nest as little as possible, thus drawing less attention to the nest. This gives the nest less "color", as the natives say, for the parents would come and feed the chicks only twice a day (between 9:30 and 10:00 a.m.; and again at dusk, between 6:00 and 6:30 p.m.). All the other time was spent away from the nest-but always with at least one parent bird being at close visible/vocal range of the nest tree. I did observe that in the first few weeks of hatching, the parents stayed a bit closer to the nest, generally in the boughs of the nest tree itself. This was possibly to protect the newly hatched chicks from the White-throated Jays (Calocitta formosa) that would frequent the nest tree, and from the Collard Aracaris (Pteroglossus torquatus) who were nesting in the same tree.