Predação e dispersão de sementes pelos psitacídeos Aratinga leucophthalma e Aratinga aurea

Abstract

The knowledge of the diet of the animals in the nature supplies important information on the ecology of these animals, being useful for several practical applications, including the acquittal and readjustment of captive animals. This study had as objective (1) to identify the vegetal species consumed by two species of psittacids, Aratinga aurea and A. leucophthalma, separating them in exotic and natives, (2) to describe which part of each species of plant were consumed (seeds, pulp, sprouts/leaves or flowers), (3) to evaluate the potential of these birds as seeds dispensers, from the treatment given to the consumed fruits, (4) to analyze if there were differences in the diet between two stations, dry and rainy and (5) to verify the degree of overlapping of the diet between two species. The study was made in the campus of the Universidade Federal Rural do Rio de Janeiro in the period between November of 2009 and October of 2010. Walking in tracks and in preexisting roads had been made in the campus, in the periods of the morning and the afternoon, totalizing approximately 24 hours of observations for month. It has been considered an alimentary register every time that a group of individuals was observed consuming parts of determined plant. For each register it were observed the consumed part of the plant (seeds, pulp, sprouts/leaves or flowers), the behavior of the birds when manipulating the resource and the place, dates and hour of the observation. In the case of the fruits it was still observed if they consumed it on the same plant they took it or in other places. Each consumed plant was related with the species, having been classified as native or exotic. Differences in the diet between the stations rainy and dry for each species had been evaluated through the ratio of the different alimentary item consumed at each station. To evaluate the degree of over lapping of the diet between the species, the index of Pianka was used. In 217 hours of observation 138 alimentary registers had been gotten, being 94 (63.5%) of A.aurea and 54 (36.5%) of A. leucophthalma It had been identified 26 species of plants used by the animals, belongings to 11 botanical families, of which eight were native 15 were exotic and one was not identified. Of the consumed species, seven had been used by the two species, 14 exclusively by A.aurea and only five by A. leucophthalma. For A.aurea the alimentary item with bigger amount of registers had been the fruit of palm Elaeis guineense (41.5%), while for A. leucophthalma the fruits of the eucalypt Corimbia citriodora had been the most consumed (18.5%). Seeds and pulp had been the parts more consumed of the plants, having difference between the season dry and rainy in the ratio of these items in the diet of both the species. For A.aurea the pulp consumption was higher at the dry station, while for A. leucophthalma the seeds had been the more consumed item at this season. About the birds working as seeds dispensers, the behavior of both species while feeding of ingá Inga laurina and of palm demonstrated that both were seed dispensers of those species The index value of the alimentary overlapping was low (0.31), showing that this over lapping in the diet between the two birds species is small and also these species are not competing for alimentary resource in the studied area.