Influência do gradiente urbano sobre a avifauna na cidade de Uberlândia, Minas Gerais, Brasil

Abstract

The existence of an urban gradient can influence the distribution of the local avifauna. The objectives of this work were: 1. to establish distribution (space and time) of the avifauna in a section of the urban area of Uberlândia; 2. to estimate the richness and the contact frequency of the species found in the study area; 3. to determine the existence of an urban gradient along the area and 4. to evaluate the influence of environmental parameters on the distribution of the avifauna in that gradient. They were established nine transects along three avenues of the city, disposed parallely, that are prolonged from the periphery to the center. The corners were considered observation points. The avifauna was reasearched between October of 2003 and August of 2004. The observations were accomplished about 30 minutes after dawning, in sessions of eight minutes for point. The registrations of the species were visual and/or acoustic. The number of contacts was establish through the counting method for points. The species Columba livia, Notiochelidon cyanoleuca and Passer domesticus were not counted. The registered species were classified as for the occurrence frequency. The transects were sampled in nine days a month, a totality of 432 points (57,6 hours). The urban gradient was characterized by amount of houses, buildings, urban trees, lamp posts and fallow lands, as well as the distance of each point. We found 56 species of birds (10 orders, 21 families and 49 generes). The rainy station presented larger richness (51 species) and larger number of exclusive species (n = 5). The resident species (n = 31) acted more than 55% of the registered birds. In the total, 3,746 contacts were registered. The stations differed statisticaly as for the number of contacts: 1,516 in the rainy station and 2,230 contacts in the dry station. Fourteen species of birds were classified as common (registered in all of the months), representing 88,3% of the total of registrations (n = 3,311). The initial points of the transectos presented larger number of trees and fallow lands. Richness showed significant relationship with the distance of the points to the center. Among the quantified environmental variables, those that demonstrated the existence of the urban gradient were: urban trees, fallow lands and buildings; while buildings between an and five floors, fallow lands and lamp posts had larger weight about the distribution of the avifauna.