Uso e seleção de habitat por aves em ambientes campestres e áreas úmidas na região sul do cerrado

Abstract

In Brazil, the largest remnants of the Cerrado grasslands are threatened and restricted to protected areas. They are priority ecosystems for preservation and sustain a unique fauna, with many species of conservation interest. The present study was developed in one of the largest contiguous remnants of native grasslands of the Cerrado within the protected area of the Serra da Canastra National Park (SCNP), from December 2012 to April 2016. The aim of this study was to verify aspects of habitat use and selection by the Black-masked Finch (Coryphaspiza melanotis), the Pearly-bellied Seedeater (Sporophila pileata) and the Plumbeous Seedeater (Sporophila plumbea), as well as the relationships between behavior, density of individuals (C. melanotis) or flock size (Sporophila spp.) and habitat characteristics. It was also aimed to record and identify the species of grass (Poaceae) selected for consumption by birds of the genus Sporophila that occur in the SCNP. In two transects of 20 km each, n = 20 plots with about 16 ha were established for the data collection of the Black-masked Finch, while the transects were entirely sampled for data collection of the Seedeaters. The results indicated that the Black-masked Finch selected different types of perches according to their behavioral objectives. The height of certain physical structures of the environment was one of the factors selected by this bird. The grasslands with “murundus” (earth mounds) were positively selected by the Black-masked Finch and sustained higher density of individuals, whereas altered areas were avoided. It was estimated the density of 19 indiv/Km2, considering adult males during reproductive period within all sampled areas. On the birds of the genus Sporophila, their behaviors were also associated to the selection of substrates (perches) and microhabitats. The Pearly-bellied Seedeater fed on 35 grass species and the Plumbeous Seedeater on 34 species. Grass richness was a determining factor for the size of the flocks of both birds. The occurrence of fires influenced the richness of flowering/fruiting grasses, and consequently the availability of food resources for birds. Natural environments where the species diversity of the herbaceous stratum remained high throughout the year were preferred areas for occupation. It is suggested that the diversity of perches in microhabitats of the grasslands, the heterogeneity of the mosaics of grassland macrohabitats and the high richness of native grasses should be preserved and monitored, while exotic species of invasive plants must be properly managed. Fire is an important factor for birds of the genus Sporophila and other granivorous birds that inhabit the SCNP, since it influences the dynamics of plants that offer grains, and is important for the maintenance of landscape heterogeneity. Fire management in the Serra da Canastra National Park, an Important Bird Area in Brazil, should be applied considering the response of both, the resident birds and the plants that constitute a food base for migratory species.