ORNITOLOGIA NEOTROPICAL 14: 247–262, 2003 © The Neotropical Ornithological Society AVIFAUNA OF THE NORTHERN PARAGUAYAN CHACO Kristof Zyskowski1,4, Mark B. Robbins1, A. Townsend Peterson1, Kimberly S. Bostwick1, Robert P. Clay2, & Luis A. Amarilla3 1University of Kansas Natural History Museum, Lawrence, Kansas 66045, USA. 2Guyra Paraguay: Conservación de Aves, C.C. 1132, Asunción, Paraguay. 3Museo Nacional de Historia Natural del Paraguay, San Lorenzo, Paraguay. Resumen. – Avifauna chaqueña del norte de Paraguay. – Inventarios llevaros a acabo en cinco sitios en el chaco del norte de Paraguay indicaron la presencia de 233 especies de aves, incluyendo a Mosqueta Boreal (Empidonax alnorum), la cual se registra por primera vez en el país. Se documentaron por primera vez tres especies por medio de especimenes [Chiripepé de Cabeza Gris (yrrhura molinae), Pijuí Ocráceo (Poe- cilurus scutatus) y Batará Boliviano (Thamnophilus sticturus)] y una por grabaciones de cantos [Piojito Trinador ³Serpophaga griseiceps)]. Se registraron dos especies nuevas para el chaco de Paraguay, y 22 especies nuevas para las zonas del Alto Chaco o Matogrosense (sensu Hayes 1995). Comparaciones preliminares entre sitios, junto con información adicional publicada, apoyan a la idea de que el recambio de especies de sitio a sitio es considerable en el bioma del chaco. La recien declarada Reserva de Biosfera del Chaco, si se imple- menta y se protege efectivamente, representa un paso importante hacía la conservación de la avifauna del norte del chaco. Abstract. – Surveys at five sites in the chaco biome in northern Paraguay revealed the presence of 233 bird species including one species, Alder Flycatcher (Empidonax alnorum) new for the country. Four species were documented for the first time with specimens [Green-cheeked Parakeet (Pyrrhura molinae), Ochre-cheeked Spinetail (Poecilurus scutatus), and Bolivian Slaty-Antshrike (Thamnophilus sticturus)] or tape-recordings [Gray- crowned Tyrannulet (Serpophaga griseiceps)]. Two additional species were new for the Paraguayan chaco and 22 species for the regions of Alto Chaco or Matogrosense (sensu Hayes 1995). Preliminary comparisons among sites, along with other published information, support the idea that site-to-site turnover of species is high in the chaco biome. The recently declared Reserva de Biosfera del Chaco, if effectively imple- mented and protected, will represent an important step towards the conservation of the northern chaco avifauna. Accepted 3 October 2002. Key words: Paraguay, chaco, Neotropical, faunal turnover, austral migration, conservation. INTRODUCTION areas still holding primary vegetation (Peter- son et al. 1993). Paraguay holds an important Effective biodiversity conservation depends portion – almost 25% – of the South Ameri- critically on quality data regarding the geo- can dry-forest biome called the chaco, repre- graphic distributions of species in remote senting 61% of the national territory ______________ (Madroño 1995, Vera et al. 2000). As Short 4Current address: Peabody Museum of Natural His- (1975) underscored in his treatise on the tory, Yale University, P.O. Box 208118, New chaco avifauna, northern Paraguay and south- Haven, Connecticut 06520, USA. E-mail: kris- eastern Bolivia hold the last “extensive uncut [email protected] stands” of dry woodland in the region. Given 247 ZYSKOWSKI ET AL. FIG. 1. Map of Paraguay, showing the location of the five study areas and other important features men- tioned in the text. Shading denotes the approximate extent of Paraguayan chaco. broad patterns of species turnover across the the area protected as far as the Bolivian bor- chaco (Short 1975, Kratter et al. 1993), and der recently came to fruition with presidential given that the chaco of northern Paraguay has decree 13202 of 21 May 2001, that boldly never seen detailed ornithological survey, new declared the entire northern Paraguayan inventories become important for establish- chaco (a total of 47,072.5 km², or 10% of the ing optimal strategies for conservation in the national territory) as the “Reserva de Biosfera region. Indeed, the only detailed single-site del Chaco.” This nationally recognized bio- surveys of the Paraguayan chaco are those of sphere reserve includes three existing pro- Short (1976) at Lichtenau, depto. Presidente tected areas (Parque Nacional Defensores del Hayes, and Brooks (1997) at Estancia Toledo, Chaco, Parque Nacional Teniente Agripino depto. Boqueron, both of which lie c. 250 km Enciso, and the now expanded Monumento south of our southernmost site. Natural Cerro Chovoreca) and incorporates In 1975, Paraguay decreed the 7800 km² three new reserves within the national system Parque Nacional Defensores del Chaco (Fig. of protected areas (Parque Nacional Río 1), one of the first protected areas to be estab- Negro, Reserva Natural Cerro Cabrera- lished in the country. An initiative to extend Timané, and Parque Nacional Médanos del 248 AVIFAUNA OF PARAGUAYAN CHACO Chaco). This massive area of well-preserved every day) and limited mobility (all areas habitat has seen no published avifaunal list, accessed on foot), restricted the number of with the exception of that included within the mist-nets at this site (8), which were con- rapid ecological assessment of Defensores del stantly filled with dry leaves by the strong Chaco (DPNVS 1999). The present study winds. Censuses were conducted up to c. 7 thus seeks to provide preliminary avifaunal km north and c. 5 km south of our road-based surveys for five sites in extreme northern Par- camp. aguay—two within the Parque Nacional Los At Madrejón, climatic conditions were the Defensores del Chaco, and three near the same as at Cerro León until a strong cold Bolivian border (Fig. 1). Our inventory work front arrived from the west at 19:00 (GMT-4 at the latter three sites represents the first avi- h) on 27 October 1995. By the morning of 28 faunal surveys from within the Monumento October, the temperature had dropped to 17° Natural Cerro Chovoreca and the newly cre- C with a completely overcast sky. At 15:30, ated Parque Nacional Río Negro. rain began and continued until c. 09:30 the next morning. By 17:00 on the 29 October, STUDY AREAS AND METHODS the wind had ceased and the sky had cleared completely. The sky was overcast on 30 Octo- Study areas ber. Censuses were limited to 3–4 road km Parque Nacional Defensores del Chaco. Two sites north, west, and south of park headquarters. within the Parque Nacional Los Defensores del Chaco, depto. Alto Paraguay, were sur- Cerro Chovoreca. The study site was chosen so veyed in late October 1995 by Robbins, as to be situated as far north as possible in the Zyskowski, Rosalía Fariña, and Sergio Villan- dry forests of the Paraguayan chaco. The ini- ueva. The first, Cerro León (20°26’S, tial goal was to arrive at the Bolivian border 60°19’W), was surveyed from the evening of (Cerro Chovoreca, Hito VII; Fig. 1). How- 21 October through the morning of 25 Octo- ever, access from the direction originally ber. The second site, Madrejón (20°40’S, planned (via Base Aérea Adrián Jara, or Base 59°50’W; c. 54 road km E of Cerro León), 5) proved impossible, and the main access was surveyed from the afternoon of 25 route (Picada Chovoreca) was both impass- October through the early morning of 31 able and surrounded by naturally disturbed October 1995, and briefly (c. 5 h) by habitat (perhaps an old burn) within a few Zyskowski, Bostwick, and Peterson on 17 kilometers north of Linea 3. For these rea- September and 10 October 1999. sons, activities were focused along Picada Conditions at Cerro León were extremely Chovoreca immediately south of Linea 3 (cen- windy, hot, and dry. Strong winds, from ter 19°35’S, 59°16’W) in an area of about 10 the northeast and east, persisted day and km2. Sampling was carried out during 19–24 night for virtually our entire stay at Cerro September 1999 by Zyskowski, Peterson, León. Temperatures peaked at 42° C by Bostwick, and Amarilla. mid-afternoon and remained at 40° C until The study site included two principal hab- after sunset. Surface water was limited to two itat types: relatively tall dry forest and scrubby shallow (one a few cm deep, the other about woodland. The forest was 10–15 m tall, with a 30 cm deep) pools. Most trees and bushes fairly uniform canopy. At the time of our were either devoid of leaves, or still in the pro- fieldwork, just prior to the normal onset of cess of losing them. The above conditions, rains and following four months of drought, combined with very limited shade (cloudless only about 5% of trees had leaves. The 249 ZYSKOWSKI ET AL. scrubby woodland averaged 1–3 m tall, with dry forest at Estancia Triunfo, c. 14 road km occasional tall trees and palms. There, essen- W of Bahia Negra (20°06’S, 58°16’W). This tially none of the vegetation had leaves. This privately-owned ranch included a small patch habitat appeared to be the result of a combi- (c. 12 x 7 km) of relatively undisturbed dry nation of topographic effects (low-lying ter- forest adjacent to the more degraded scrub rain) and disturbance, perhaps a major forest and pastures. Censuses and mist-netting were fire. We found no surface water, which led to conducted along a 7 km long narrow hunting serious problems with moisture-seeking hon- trail that traversed the patch, and along the eybees (Apis sp.). Both habitats were sampled, last 5 km of the access road. The forest was although efforts focused more on the forest about 15 m tall and carpeted with terrestrial (about 70% of effort) than on woodland bromeliads (Bromelia serra). The only standing (30%). water in the area was two artificial, 10 m diameter ponds along the main road. Despite Estancia 42.