JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. University of California Press and AmericanOrnithologists' Union are collaborating with JSTOR to digitize, preserve and extend access to Ornithological Monographs.Abstract. -This paper reports the findings of several surveys of the avifauna of the region surrounding the town of Alta Floresta, Mato Grosso, Brazil. We recorded a total of 474 species, many of which are regional endemics, which makes Alta Floresta one of the richest known sites in Brazil and all of eastern Amazonia. We provide information for a number of species range extensions and for species for which there were few previous records for Brazil. We also provide information on the vocalizations, foraging ecology, and habitat preferences for many rare or localized species that are poorly known. Of particular interest to us were a number of birds that, at least locally, are restricted in distribution to stands of spiny bamboo (Guadua sp.). The relevance of our findings to previously conducted surveys, current biogeographic hypotheses, and the many urgent regional conservation problems (including conservation priorities), are discussed.Resum£n. -Apresentam-se os resultados de varios levantamentos ornitologicos da regiao pr6xima a Alta Floresta, Mato Grosso, Brasil. Tendo um total de 474 especies, inclusive muitas endemicas da regiao, Alta Floresta 6 um dos sitios mais ricos do Brasil e de toda a Amazonica oriental. Descrevemos extensoes de distribuigao de varias especies, muitas dessas tendo puocos registros no pais. Tambem descrevemos vocaliza96es, ecologia de forrageamento, e preferencia de habitat em algumas especies raras ou mal conhecidas. Particularlmente interessantes sao especies que, pelo menos localmente, sao restritas a tabocais (bambuzais de Guadua sp.). Discutimos os resultados no contexto de levantamentos anteriores, hipoteses biogeograficas, e problemas urgentes regionais de conserva9ao.The Alta Floresta region (centered at 9°41'S, 55°54'W) sits astride the Rio Teles Pires, a principal tributary of the Rio Tapaj6s, in extreme north-central Mato Grosso near the border with Par£ (Fig. 1). It is located in the southern fringe of forested Amazonia, an area suffering alarmingly from rapid deforestation and environmental degradation (Oren and Albuquerque 1991). The accumulating impact of this devastation readily could be seen in return visits to Alta Floresta during the few years of this avifaunal survey. The threat to the region creates an urgent need to inventory its biological resources and to identify representative habitats for conservation.Knowledge of the avifauna of the Alta Floresta region also affords an opportunity to explore important biogeographical issues. Alta Floresta lies in the contact zone b...

A new species of tyrant flycatcher (Suiriri islerorum) is described from the cerrado region of Brazil and adjacent eastern Bolivia. The species previously had been confused with Suiriri suiriri affinis, with which it is syntopic at multiple sites. The new species was first identified by voice. Although cryptically similar to S. s. affinis in many respects, the new species is readily identified by all vocalizations, bill size, color pattern of the tail, and shape of the central rectrices. Most distinctive are the male–female duets, which are accompanied by dramatic wing-lifting displays not performed by any congeners. Reciprocal playback experiments of tape-recorded vocalizations demonstrated that the new species and S. s. affinis do not respond to one another's vocalizations. We provide information on the natural history of the new flycatcher, along with spectrograms of its various vocalizations. We also provide vocal analysis of all other named taxa in Suiriri, and discuss the various intrageneric relationships. In particular, S. s. affinis and S. s. bahiae, although distinct morphologically, are vocally and behaviorally similar, and respond to one another's vocalizations in playback experiments.

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