The avifauna of the Brazilian state of Roraima: Bird distribution and biogeography in the Rio Branco basin

Abstract

The Brazilian state of Roraima represents a meaningful biogeographical unit, enclosing the entire basin of the Rio Branco, a major river in the Amazon basin. Roraima is also an area of high habitat diversity where terra fi rme forest, seasonally fl ooded forest, white-sand forest, savanna, gallery and dry forest, and the vegetation associated with the tepuis, all occur within a relatively small area (225,000km2) by Amazonian standards. We provide the fi rst comprehensive compilation of the avifauna of the state in forty years. We integrated the results of our own fi eld work, where we recorded 512 bird species, with data gathered from museum specimens and from published sources. We present a list of 741 bird species for the state of Roraima, 38 of which are mentioned for the fi rst time for the state. We also provide a list of 15 species previously cited for Roraima that we consider hypothetical, and predict the presence of another 69 species that we consider likely to be recorded in the state with further fi eld work. We also present details on some of our most interesting records, which include the fi rst Brazilian specimen of Atalotriccus pilaris, and the second locality for Brazil of Myrmeciza disjuncta. We conclude that habitat heterogeneity (beta-diversity) is responsible for 60% of the avian diversity of Roraima, whereas regional endemism (gamma-diversity) accounts for about one third of the bird species occurring exclusively in terra fi rme forests. We analyze the biogeographical patterns of avian distributions within the state, in relation to the different habitats present in Roraima, and discuss some of the main conservation problems in the state of Roraima, driven by the expansion of monocultures such as soybean, acacia, and rice plantations which are putting at risk large expanses of savannas, wetlands, dry and gallery forests.