A comparison of bird communities in natural and disturbed non-wetland open habitats in the Cerrado's central region, Brazil.

Abstract

In the Cerrado of Brazil, the largest Neotropical savanna region, open habitats are suffering an intense process of conversion to pasture and agricultural land. This study evaluated the responses of birds to the thinning of tree and shrub cover in plots of cerrado sensu stricto, the dominant habitat in the region, and examined whether disturbed plots supported bird communities of open natural habitats with similar structure. Birds were censused by point counts in five disturbed sites and in seven preserved patches, with a total of 304 samples of 20 minutes in 68 points. Cleared plots were not suitable for species strongly dependent on trees and shrubs, such as frugivores and most insectivores. Their abundance was associated with the complexity of vegetation structure in these plots. Shrubby pastures held about 120% more species than the traditional cleared ones. Bird communities of pastures showed large differences in relation to those of grasslands with similar structure. Communities of pastures were dominated by a seedeater, the Blue-black Grassquit Volatinia jacarina, and most species were habitat generalist or oportunistic predators, such as raptors and insectivores. Obligate grassland species, like the Grass Wren Cistothorus platensis, Cock-tailed Tyrant Alectrurus tricolor and Black-masked Finch Coryphaspiza melanotis, as well as other abundant species in grasslands, such as Sharp-tailed Grass-tyrant Culicivora caudacuta and Capped Seedeater Sporophila bouvreuil do not adapt to pastures. Grassland grasses probably do not recover spontaneously in abandoned pastures and in other agricultural lands. Thus, conservation of grassland birds will strongly depend on a urgent programme of identification and protection of large areas of Cerrado dominated by campo limpo and campo sujo. These species would also benefit from the maintenance of a band of grassland along gallery forests.