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Avifauna of a Locality in the Upper Orinoco Drainage of Amazonas, Venezuela

1997; Issue: 48 Linguagem: Inglês

10.2307/40157572

1941-2282

Kevin Zimmer, Steven Hilty,

Botany and Geology in Latin America and Caribbean

This paper reports the findings of several surveys of the avifauna of the region surrounding two remote fishing camps in the upper Rio Orinoco region of Amazonas, Venezuela. This area is of particular interest because it has been little-explored by ornithologists, and because of the predominance in the region of habitats derived from white-sand soils. We provide information on a number of range extensions, including one species (Pale-bellied Mourner, Rhytipterna immunda) for which there were no previous records for Venezuela. We also provide information on the vocalizations, foraging ecology, and habitat preferences for many rare or poorly known species, including Mitu tomentosa, Neomorphus rufipennis, Notharchus ordii, Myrmotherula cherriei, and Hylophilus brunneiceps. Our observations of Hylophilus brunneiceps also have taxonomic implications. The soil-based insularity of the local terra firme habitat as a factor limiting local bird distributions is also discussed. Resum£n. Este papel reporta los encuentros de varios reconocimientos de la avifauna de la region rodeando dos campamentos de pezca remotos en la parte superior del Rio Orinoco en la region de la Amazonas, Venezuela. Esta area es de interes particular porque se ha explorado poco departe de ornitologos y porque la predominancia de habitaciones en la region se diriven de terrenos de arena-blanca. Proveemos informacfon sobre varias extensfones, incluyendo un especie {Rhytipterna immunda) por el cual no se encuentran archives anteriores en Venezuela. Tambien proveemos informacfon sobre las vocalizaciones, forraje ecologico, y habitaciones preferidas departe de muchos especies raros 6 poco conocidos incluyendo Mitu tomentosa, Neomorphus rufipennis, Notharchus ordii, Myrmotherula cherrei, y Hylophilus brunneiceps. Nuestras observacfones de Hylophilus brunneiceps tambien tiene implicaciones taxonomicas. La insulacion de la base terrena cercano, habitaciones terra firme, como punto que limita la distribucion de pajaros tipicos tambien se di scute. In February 1990 we began surveying the birds in the area surrounding a small fishing camp, Campamento Junglaven, in the interior of the Territorio Federal de Amazonas, Venezuela, at approximately 05°06'N, 66°44'W (ca. 156 km E-SE from Pto. Ayacucho), south and east of the Rio Orinoco and northwest of the Rio Ventuari (Fig. 1). The camp is located on the left (east) bank of Creek, a small tributary flowing south into the Rio Ventuari. A second nearby fishing camp Camani Camp is on the north bank of the middle Rio Ventuari, between the Indian village of and the mouth of the Rio Manapiare. The area is completely undeveloped except for the two camps and ca. 15 km of sandy roads connecting them to the shared airstrip. Access is limited to boat or small aircraft. Annual precipitation is ca. 2,550-3,000 mm, much of it concentrated in June through October (Schwerdtfeger 1976). There is a pronounced November-May dry season. The surrounding area contains a mosaic of different soil types that support a natural patchwork of distinct vegetation types. Much of the area is dominated by white-sand soils covered by grassy savanna with scattered shrubs (1-3 m in height) and small stands of Mauritia palms. Bordering these savannas are scrubby, low-canopy (3-10 m) woodlands (= savanna woodlands) that are also found on white-sand soils. These woodlands are dense, with an understory that is often nearly impenetrable. They are somewhat deciduous, with a partially open canopy, and are seasonally flooded (June-October). Scattered lagoons and oxbows within these woodlands retain standing water throughout the dry season (November-May). The Ventuari and its many small tributaries are flanked by wide bands of taller (15-25 m) forest that grows on yellow-clay soils and is seasonally flooded. This vdrzea forest is characterized by a more closed canopy with a fairly open understory and an abundance of vines and lianas. Farther from the river, large isolated