Forrageamento de beija-flores (Aves: Trochilidae) em bebedouros artificiais, em áreas urbanas e naturais no bioma Cerrado

Abstract

The remnants of green areas and natural habitats in urban environments play an important role as an ecological refuge for many bird species. The Cerrado biome (Brazilian savanna) presents marked seasonality and a mosaic of vegetation types that influence occurrence and behavior of the birds, but their natural remnants in urban areas remain threatened by progressive occupation. The hummingbirds act as pollinators of several species of Cerrado plants, but effects of urbanization on the behavior of this group remain poorly known. This study addresses the following questions: (i) Can the species of hummingbirds and their pattern of visitation to food resource vary between urban and natural habitat patches? (ii) Can their agonistic interactions vary between species and types of environment? (iii) Are there any seasonal, temporal or daily patterns on their foraging strategies and observed behaviors? To address these issues, we conduct observations in three squares, two urban parks, and three ecological reserves, in areas of Cerrado biome (Brazilian savanna), Uberlândia municipality, Minas Gerais State. We classified the observation sites based on the level of conservation and urbanization into four environmental categories: (1) squares and (2) parks, in the center of urban area; and (3) savanna and (4) forest, inside the two biological reserves beside the urban area. Three points of observation (n = 12 in total) were distributed in each environmental category, using an artificial feeders with 20% sucrose solution at each point. We observed the behavior of hummingbirds species based on the focal animal method; observations (total of 600 h) occurred from January to September, between 7:00-12:00 hours in the morning. Ten species of hummingbirds visited the artificial feeders (N= 3,100 visits) in all environments, with Eupetomena macroura, Thalurania furcata and Amazilia fimbriata, as the most common species. Urban parks and savannas had the largest number of species (N = 8) and visits, while squares housed only three species. The similarity between hummingbird communities in the different environments was determined mainly by the structure of vegetation (open or closed), more than urbanization gradient. In closed vegetation, T. furcata was the dominant species and more territorialist, but, in open vegetation, was E. macroura. The savanna environment showed the greatest number of agonistic interactions. Urban parks housed six dominant species, but squares, only one species, E. macroura. During the morning, there was a decline in the visitation of hummingbirds in squares and savannas, but in urban parks and forests, their visitation remained constant. All environments, excepted squares, had more visits at dry season. Hummingbirds’ species composition differed in the environments between the dry and rainy season. In natural habitats, more species occurred at the dry season and, in urban areas, more species occurred in the rainy season. The similarity of species among habitat patches with open or closed vegetation was higher in the rainy season. Agonistic interactions were more frequent at dry season. Hence species composition, the patterns of visitation, of territorialist behavior and the daily or season variations at hummingbird community, should be determined mainly by vegetation structure of their habitats and also by variations in availability of food resources, possibly associated to landscape conservation and urbanization gradient.