Oferta de frutos e frugivoria por aves, em espécies do gênero Miconia Ruiz & Pav. (Melastomataceae) em duas áreas do Cerrado

Abstract

The goals of this study were: to determine the seasonality, duration and fruit supply peaks of Miconia albicans, M. ibaguensis, M. affinis, M. theaezans and M. chamissois; to verify the nutritional quality of these fruits (Chapter I); to evaluate which birds feed on these fruits, and to verify which birds are the main dispersers of each Miconia species (Chapter II). The study was carried out from January to December 2009 in two Cerrado areas: Estação Ecológica do Panga (EEP) and Fazenda Experimental do Glória (FEG), at Uberlândia, MG. The phenological observations were made every two weeks, in order to assess the quantitative immature and mature supply of fruits, for each species. Miconia species offered fruits along the year, with an asynchrony between species. All species presented significant fruit peaks at the wet season, where fruit supply was more concentrated. The main climatic factors influencing the fruit supply were temperature and precipitation; in both areas this influence was higher for immature fruits supply. The Miconia species were similar in relation to nutritional content, except for M. affinis, which presented the highest levels of lipids, proteins and minerals. The carbohydrate levels at EEP were higher than those at FEG, and the inverse was observed for water content, indicating a relation between water and carbohydrate content. The nutrient levels were influenced negatively by temperature. The focal observations of Miconia fruit consumers were carried out for M. theaezans, M. albicans and M. chamissois, to determine the potential dispersers of these species, through feeding behavior. Thraupidae was the most frequent family on M. theaezans and M. chamissois, while Emberizidae and Tyrannidae were the most frequent on M. albicans. Species that offered fruits at the dry season (M. theaezans and M. chamissois) were more visited, and their fruits were more consumed than species that presented fruits at the wet season. The number of consumed fruits was proportional to the time birds remained on the plant. The most common foraging tactic used during fruit consumption, for all species, was perched , which varied from 68.83% to 100% visits, depending of the Miconia species. The most common foraging tactic used was swallower (M. chamissoi e M. albicans, in both areas), followed by the strategy of masher-and-swallower (M. theaezans). From the total records for Miconia, the omnivorous guild was predominant in relation to visitors (57.14%) and visits (83.16%), a pattern shared for all species.