j. Field Ornithol., 64(4):549-556 NORTH AMERICAN MIGRANT PASSERINES AT TWO NON-FORESTED SITES IN VENEZUELA BETSY TRENT THOMAS Waterfield,Rt. 1 Box 212 C Castleton,Virgznia 22716 USA Abstract.--Fourteen speciesof passerinenearctic migrants to the neotropicswere observed at two non-forestedsites in interior Venezuela, over >20 yr. Eleven specieswere found in a secondary-scrubhabitat in northern Venezuela and 12 were observedat a site in the central llanos. Behavioral notesare reportedin addition to extensionsof monthsof occurrence for five species,and sevennew state records. PASERIFORMES MIGRATORIOS EN DOS LOCALIDADES NO-FORESTADAS DE VENEZUELA Sinopsis.--Enun perlodo>20 aftos,se han observado14 especiesde paseriformesmigra- torlos del neofirtico en dos localidades no-forestadas del interior de Venezuela. Se encontraron 11 de las especiesen habitat caracterizadocomo matoffal secundariode la parte norte de Venezuela,y 12 en una 1ocalidadde los llanoscentrales. En el trabajose informanademfis 7 nuevosregistros para estadosde Venezuela,se discuteel perlodode estadlade cincode las aves,y se ofrecengeneralidades sobre la conductade las 14 especies. Currently there is concernabout the diminishingnumbers of some North American migrants to the neotropics(Keast and Morton 1980, Rappole et al. 1983, Robbinset al. 1986, Terborgh 1989). To address this problem, numerousauthors call for more detailedobservations of nearcftcmigrants on their wintering grounds(see Hagan and Johnston 1992). Most North American passefinemigrants to the neotropicsare found in forestedhabitats (Rappole et al. 1983), but Leck (1985) in Mexico, Karr (1976) in Panama, and Robinson et al. (1986) in Peru, reportedthat high numbersare alsofound in edge,scrub and secondary habitats. In Venezuela nearcticmigrants are reported to be found from coastalmangroves to montanewet forestsat > 3000 m (Meyer de Schauen- seeand Phelps 1978). I found 14 nearcticpassefine species at two climatically harsh, low altitude, non-forestedVenezuelan sites. Both sites regularly experience an approximately5-6-mo dry seasonfrom about November through April at the time migrantsare generallypresent. The migrantsappeared to be transients at both sites, although at some places a few may spend the boreal winter (McNeil 1982, Schwartz 1964). Some nearctic migrants used the same harsh, non-forestedsites on their northward journeys at the extreme height of the Venezuelan dry season. The regionalfield guide(Meyer de Schauenseeand Phelps1978) gives months of occurrence,elevation rangesand Venezuelan statesfor most species.This paper extendsthose months of occurrencefor five species, addsseven new states,and givesbehavioral notes for all 14 species. 549 550] B.T. Thomas J.Field Ornithol. Autumn 1993 STUDY SITES AND METHODS One studysite was 30 km southof Caracas,in the south-facingfoothills of the Costal Cordillera at Urbanizacion Los Anaucos(10ø19' N, 66ø51'W), state of Miranda. I lived there, and studied the birds from 1966 to 1984, making brief visits in 1985, 1987, 1988 and 1993. The secondsite was 45 km southof Calabozo,state of Gufirico,at FundoPecuario Masaguaral (08ø31'N, 67ø35'W), where I studiedbirds from 1971 to the present.At bothsites most annual rainfall wasbetween May and November(Thomas 1985) with a strongdry seasonin between,during which many of the predominantly deciduoustrees were bare. The Los Anaucossite (elevation 550-800 m; 141 ha) consistedof secondary-scrubwith much mesquite (Prosopisjulifiora)and a few widely scatteredhouses surrounded by yards and gardens.The original forestcover of this area was lost over 400 yr ago with the earliestarrival of Europeans.Masaguaral (elevation63 m; 10,000 ha) is a large cattle ranch with grazed fields, widely scattered large treesand somegallery forest,although few observationswere made in the gallery forest.The llanoshabitat, althoughused by humans,may not be greatly modifiedfrom its statebefore European colonization. For more detailed descriptionsof the sites,and their avifauna by month, breeding and abundance,see Thomas (1979, 1993). I kept lists of all speciesobserved at both siteswhile I studiedendemic South American birds. Although I mist-nettedat both sites,only a few (n -- 16) nearcticmigrants were capturedincidentally to other work, as comparedwith >2100 neotropicalbirds. Weights of thosebirds are in Thomas (1982, 1990). One speciesoccasionally recorded at both sites, the Red-eyedVireo (Vireo olivaceus)is not consideredbecause I couldnot separatesightings of residentraces from migrants.For non-flockingbirds the total numberfound is indicatedin parenthesisfollowing the sitename. RESULTS Bank Swallow(Riparia riparia).--Masaguaral only. On 26 Apr. 1983 I mist-netteda single bird that had an incompletechest band, but two other individualsflying overheadhad completechest bands; usually 5- 100 Bank Swallowswere observed,often with much larger flocksof the next species,in December, January, February and April. Meyer de Schauenseeand Phelps(1978) reportonly October-Novemberoccurrence in Venezuela, and none from Gufirico. Barn Swallow(Hirunclo rustica).--Los Anaucos.Once, on 10 Dec. 1969. Masaguaral.This specieswas commonin the llanosbut foundirregularly in all monthsexcept June-August; flocksvaried from 10-100 birds, but over 5000 roosted< 1 km from Masaguaralin January-February 1976. On 26 Apr. 1983 a large volumeof water was pumpedinto a drying lagoon starting at 0800 hours. By 1130 a flock of about 40 swallows appearedand foragedas low as 20 cm alongthe advancingedge of fresh water, exploiting a suddenlyavailable sourceof prey. Large numbersof transient Barn Swallowscongregated at the Gufirico Dam, closeto Cala- bozo,from mid-April throughearly May of eachyear. Vol.64, No. 4 NearcticMigrants in Venezuela [551 Veery(Catharusfuscescens).--Los Anaucos (2). On 31 Oct. 1983; on 20 Oct. 1981 a Veery wasattracted out of thickunderbrush to a commotion causedby residentbirds at a rare ant swarm,but it did not remainthere. Willis (1966) reportedthat Veeriesin Panamaare regularlyattracted to ant swarms.Masaguaral (4). On 25 Oct. 1978 a singlebird twice ate the ripe red fleshof the commonannona fruit (Annonajahnii). A Veery mist-nettedon 3 May 1985 had freshlymolted remiges, but worn and brokenrectrices, and was missingthe distal 3 mm of the culmen.This Veery weighed44.4 g, well overthe average31.2 g of migratingVeeries in Pennsylvania(Dunning 1984), suggesting,in spiteof bill damage,that it had good migratory fat reserves.Meyer de Schauenseeand Phelps (1978) had no recordsfor May nor any as low as 63 m, and no records for Miranda or Gufirico. Gray-cheekedThrush (Catharus rninirnus).--Los Anaucos (2). One found with a ConnecticutWarbler (Oporornisagilis) on 27 Apr. 1969 in open scrub;another on 7 Nov. 1983. Masaguaral (3). Two different birds netted there on 15 and 16 Nov. 1980, both in open scrub. TennesseeWarbler (Verrnivora peregrina).--Los Anaucosonly (5). On 4 Apr. 1968 a bird ate smallfruits from a nativevine; two birdschased eachother 21 Apr. 1970 while both appearedto be foragingamong seeds of a thick-leavedepiphyte; on 20 Jan. 1980 a mist-nettedbird had its foreheadstained pink, possiblyfrom the red pollenof a Combreturnspp. vine, a nectar source.In January and February these warblers were frequently seen in Colonia Tovar (state of Aragua) with their entire foreheadsand throatsheavily stainedpink. Morton (1980) describessim- ilar stainingof TennesseeWarblers in Panama.On 4 Apr. 1982 a bird foraged in the lower outer branchesof a semi-leaflessmasaguaro tree (Albiziaguachapele), by flitting out to the freshlyfoliated branch tips. At the sametime a male American Redstart (Setophagaruticilla) foragedin the uppercenter branches just belowthe thin canopy.Both birds appeared to be gleaningtiny prey in the emergingfoliage. Yellow Warbler (Dendroicapetechia).--Los Anaucos(16). Birds were seenin November,February, March and April; on 5-7 Feb. 1969 a bird returned repeatedlyto a yard to feed on small insectson an apamatetree (Tabebuia rosea);31 Mar. 1982, four birds spent time in a masaguaro tree, the next day from 0935 to 1003 hoursat least 10 Yellow Warblers in partiesof 3-5 fed quickly by gleaninginsects attracted to the blossoms of a floweringavocado tree (Perseaamericana), along with three resident species.Masaguaral (12). Seenin all monthsOctober-March; a 1 Nov. 1977 bird caughtand ate a 2 cm pale buff-coloredadult lepidoptera;7 Feb. 1984 a Yellow Warbler sangbriefly from low bushes;11 Mar. 1991 a bird in fresh plumage foragedin bushesat 0.50-1.50 m. For about 12 min on 13 Mar. 1991 a Yellow Warbler foragedalong an 8 cm diameter, nearly horizontalbranch of a large leaf matapalo(Ficus spp.) by hopping alongthe branchand probingall the leavesit couldreach from the branch. On 14 and 15 Mar. 1992 a bird sang as it foragedin low trees and hedgerowbushes but apparentlyleft the area as it was not found there 552] B.T. Thomas J.Field Ornithol. Autumn 1993 again. All observationswere presumablyof the migrant subspeciesD. p. desrivabecause the polytypicresident Yellow Warbler is confinedto man- grovesalong the Caribbeancoast (Meyer de Schauenseeand Phelps1978). Blackpoll Warbler (Dendroicastriata).--Los Anaucos(3). A male was seenon 16 May 1966; on 11 May 1976 a female in fresh plumage ate tiny (<2 mm) insectsfrom the branchesof an avocadotree; on 13 Oct. 1981 an immature plumagedbird fed actively in the lower canopyof a mesquitetree (Prosopisjuli flora ). Masaguaral (1). On 21 Oct. 1979 a bird in immatureplumage fed in leavesof the upper branchesof