The Condor92~947-960 8 The cooper onlithologid society1990 NORTH AMERICAN BIRD MIGRANTS IN PARAGUAY ’ MuseoNational de Historia Natural de1Paraguay, SucursaIl9, Ciudad Universitaria, San Lorenzo, Paraguay STEVEN M. GOODMAN~ Mu.wumof Zoology, The Universityof Michigan, Ann Arbor, MI 48109 JENNIFERA. Fox4 AND TARSICIO GRANIZO TAMAYO~ Centro de Dates para la Conservacibn,Casilla de Correo 3303, Asunci6n.Paraguay NANCY E. ~PEZ Muse0 National de Historia Natural de1Paraguay, SucursalI9, Ciudad Universitaria, San Lorenzo, Paraguay Abstract. The status of North American bird migrants in Paraguay is reviewed and summarized. Observations (from 1987-1989) are reported for 29 of the 32 speciesdocu- mented from Paraguay.New extreme migration dates, maximum counts,and distributional records are reported for many species,including six speciesof North American migrants documented from Paraguayfor the first time: Peregrine Falcon (Falco peregrinus),Black- bellied Plover (Pluvialis squatarola), Red Knot (Calidris canutus), Sanderling (C. alba), Arctic Tern (Sterna paradisaea), and Purple Martin (Progne subis). Paraguay’s Nearctic migrant fauna is dominated by aquatic nonpasserines,especially shorebirds; terrestrial non- passerinesand passerinesare poorly represented.Paraguay ’sfauna is depauperatecompared with other Neotropical areasto the north, presumablydue to its southernand inland location. Most migrant speciesfeed primarily on invertebrates. More speciesinhabit wetlands than dry areas. Key words: Bird migration; distribution;food use;habitat use;North America; Paraguay: seasonality. Resumen. Se resume el estado de las aves migrantes norteamericanasen el Paraguay. Se informa en relaci6n alas observaciones(desde 1987 hasta 1989) para 29 de las 32 especies documentadaspara el Paraguay.Se presentandatos referentesa nuevas fechas extremas de migracibn, censosmaximos y registrosdistribucionales para muchas especies,incluyendo seisespecies de migrainesnorteamericanas documentadas para el Paraguaypor primera vez: el Hal&n Peregrino (Falco peregrinus),Chorlo Artico (Pluviahssquatarola), Player0 Rojizo (Calidris canutus), Playerito Blanco (C. alba), Gaviotln Artico (Sterna paradisaea) y Go- londrina Purpurea (Prognesubis). La fauna m&ante neartica de1Paraguay esta dominada por las aves acuaticasno-paserinas, especialmente10s playeros; las aves terrestres no-pa- serinasy las paserinase&n pobremente representadas.La fauna paraguayaes pequefia en comparacidn con otras areas neotropicales m&s al norte, presumablemente debido a su ubicacion meridional y lejos de1mar. La mayoria de las especiesmigratorias se alimentan principalmente de invertebrados. Se encuentran mls especiesen humedales que en areas secas. INTRODUCTION ’ Received 12 February 1990. Final acceptance 15 Although more than half of the Nearctic breeding July 1990. bird speciesspend at least part of their lives as *Present address: Department of Biology, Loma Linda University, Loma Linda, CA 92350. migrants in Neotropical areas (Rappole et al. 3 Presentaddress: Department ofZoology, Field Mu- 1983), much remains to be learned of their dis- seumof Natural History, RooseveltRoad at Lake Shore tribution, abundance, and seasonality in many Drive, Chicago, IL 60605. areas of the Neotropics. In the Republic of Par- 4 Present address:11 Orrantia Circle, Danvers, MA aguay, where previous ornithological researchfo- 01923. 5Present address:Avenida Venezuela 2225, Quito, cused primarily on the distribution and taxon- Ecuador. omy of local breeding species, a paucity of 19471 948 FLOYD E. HAYES ET AL. published information exists on the occurrence by undulating or precipitous hills, none exceed- of North American migrants. In this paper we ing 800 m in elevation. report our observations, from 1987-1989, of 29 Precipitation in Paraguay is lowest in the west- speciesof North American bird migrants in Par- em Chaco, averaging lessthan 500 mm annually aguay, and review the status of all species re- in some areas, and highest in southeastern Par- ported from the country. New extreme migration aguay where an average of over 1,700 mm of dates, maximum counts, and distributional rec- rain falls annually. The distribution of precipi- ords are reported for many species,including six tation is highly seasonalin the Chaco, where rain speciesdocumented from Paraguay for the first seldom falls during the dry season,from June to time. We also compare the migrant fauna of Par- October, yet causesextensive flooding during the aguay with several other Neotropical areas and wet season, from November to May. The same discussfood and habitat use of migrants. seasonal pattern holds true for the Oriental re- gion, although rainfall is more evenly distributed ECOLOGICAL ZONES AND CLIMATE during the year and more frequent than in the Situated in the interior of south-central South Chaco. Temperatures in Paraguay often exceed America, the land-locked Republic of Paraguay 40°C during the austral summer, and occasion- comprises an area of 406,752 km*. The country ally dip below freezing during winter, thus sub- is divided by the southward-flowing Paraguay jecting large portions of the country to occasional River into two distinctive regions (Fig. 1). To frost. Mean annual temperatures range from less the west, the Chaco region is essentially a vast, than 2 1°C in southeasternParaguay to over 25°C relatively flat alluvial plain gradually sloping in the northeastern Chaco. downward toward the Paraguay River from the Andean foothills. The northwestern portion of SPECIES ACCOUNTS the Chaco is arid and characterizedby xerophytic In the following accounts, species enclosed by vegetation. Further east, toward the Paraguay brackets are presently regarded as hypothetical River, the scrub forests gradually become taller in Paraguay. Figure 1 showsthe location of each and more scatteredas the terrain becomesdom- of the 19 departments (Dept.) of Paraguay; de- inated by seasonally inundated palm savannas. partments are identified only at the first mention The northeastern comer of the Paraguayan Cha- of a specific locality. Geographical coordinates co is more heavily forestedthan the lower Chaco are given for localities not listed in Paynter (1989). and is ecologically similar to the Pantanal of ad- Seasonal references pertain to the boreal cycle jacent Bolivia and Brazil. becauseNorth American bird migrants winter in East of the Paraguay River, the more topo- the southern hemisphere even though locally it graphically diverse Oriental region comprises a is summer. “Migrant” refers to birds passing mosaic of habitats. Xerophytic Chaco forma- through during fall and spring; “visitor” refers tions persist along the east bank of the river in to birds remaining during winter or summer. some areas, gradually yielding to taller and more Abundance terms are defined as follows: com- humid deciduous foreststo the east. The north- mon, observed daily in appropriate habitat; fair- eastern comer of the Oriental region is domi- ly common, observed every other day on aver- nated by a peculiar scrub forest formation re- age;uncommon, observed once every 2- 10 days; ferred to as camposcerrados. The upper Parand rare, observed at intervals of 10 or more days. River basin of the southeasternpart of the Ori- Nomenclature and sequenceof speciesfollow the ental region was once dominated by tall humid AOU (1983). forests,but as in many areas of the region, much Acronyms in addition to the authors’ initials of the forest has been cleared during the last few include: AFARP = Archive Fotografico de Aves decadesby developing agricultural communities. Raras de1Paraguay, San Lorenzo; FMNH = Field Toward the confluence of the Parana and Para- Museum of Natural History, Chicago; IML = guay Rivers, in the southwestern comer of the Instituto Miguel Lillo, Tucuman, Argentina; MAS Oriental region, the terrain is characterized by = Museo A. Schulz, Resistencia, Argentina; extensive prairies and wetlands dotted by scat- MNHNP = Museo National de Historia Natural tered patchesof scrub forests,and is ecologically de1Paraguay, San Lorenzo; MVZ = Museum of similar to the eastern Chaco. The topography of Vertebrate Zoology, University of California, the Oriental region is punctuated in many areas Berkeley; UMMZ = University of Michigan Mu- NEARCTIC MIGRANTS IN PARAGUAY 949 PARAGUAY FIGURE 1. Map of Paraguayshowing location of 19 departmentsand major rivers. Departments: 1 = Chaco; 2 = Nueva Asuncion; 3 = Alto Paraguay;4 = Boqueron; 5 = PresidenteHayes; 6 = Conception; 7 = Amambay; 8 = San Pedro; 9 = Canindeyu; 10 =-Central; 11 = Cordillera; 12 = Caaguazk 13 = Alto Parank 14 = Paraguari, 15 = Guairl; 16 = Caazapl; 17 = Neembucti, 18 = Misiones; 19 = Itapua. seum of Zoology, Ann Arbor; and VIREO = records include single birds seen by FEH along Visual Resourcesfor Ornithology, Philadelphia, the Tebicuary River at Villa Florida, border of Pennsylvania. Depts. Paraguari and Misiones (26”25’S, 57%5’W), on 12 June 1988, and along the Par- OSPREY (PANDION HALIAETUS) aguay River near Puerto Maria, Dept. Alto Par- In Paraguay, this specieshas been recorded only aguay, on 16 June 1988. SMG noted a single bird a few times along the Paraguay River at LambarC 16 km N of Antequera, Dept. San Pedro, on 15 and Asunci6n, Dept. Central (Berlepsch 1887, September 1988. A Madrofio (pers. comm.) ob- Bertoni 1914), and at Rio Negro, Dept. Presi- served four Ospreys on 22, 24, and 26 August dente Hayes (Bent 1937). A specimen in UMMZ 1989 along the Paraguay River north of Con- wascollected 40 km WSW