Habitat Selection and Foraging Ecology of Raptors in ...

Habitat Selection and Foraging Ecology of Raptors in Amazonian Peru Author(s): Scott K. Robinson Source: Biotropica, Vol. 26, No. 4 (Dec., 1994), pp. 443-458 Published by: The Association for Tropical Biology and Conservation Stable URL: http://www.jstor.org/stable/2389239 . Accessed: 23/07/2013 16:14 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp

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BIOTROPICA 26(4): 443-458

1994

HabitatSelection and ForagingEcologyof Raptorsin AmazonianPeru1 Scott K. Robinson IllinoisNaturalHistorySurvey,607 East Peabody Drive,Champaign,Illinois61820, U.S.A.

ABSTRACT Census resultsand observationsof foragingtacticsand diet werecompiledforthe 35 regularly occurringspeciesof diurnalraptorsin an 800-ha sectionof the lowlandManu National Park of southeastern Peru. Censusresultsshow thatmostforestraptorsoccurredacrossa broad arrayof successionalstages.Populationdensitiesrangedfroma high of one or two territories double-toothedkite,Harpagusbidentatus)to lows per 100 ha (e.g.,Micrasturforest-falcons, in the entirestudyarea (e.g., largeeagles). A speciesreplacement of much less thanone territory apparentlyoccurs in thegenusLeucopternis, withtheslate-colored hawk L. schistaceaoccupyingfloodplain forestand thewhite-browed hawk L. kubli occupyingupland forest.All othercongenersshowed substantialoverlapin habitatuse. Based on of over 400 preyitems being carriedand over 200 attacks,I divided raptorsinto observationsby 35 researchers from severalpreliminary guilds. Forestraptorsinclude seven species that hunt arthropodsand small vertebrates concealedperches(e.g.,Micrasturforest-falcons, gray-headedkite,Leptodoncayanensis);sevenspeciesthathuntlarge attacks birdsand mammalseitherfromconcealedperches(e.g.,ornatehawk-eagle,Spizaetusornatus)or on long-range on siteswherebirdsormammalsaggregate(e.g.,bicoloredhawk,Accipiter bicolor);and severalspecieswithspecialized diets of wasps (red-throated uncinatus),and caracara,Daptriusamericanus),snails(hook-billedkite, Chondrohierax snakes(laughingfalcon,Herpetotheres cachinnans).Species thathunton the wing includefourthat feedmostlyon and the bat falconFalco flyinginsectsand small vertebrates (two kites,the short-tailedhawk Buteo brachyurus, and two vulturesthatsearch one thatdiveson perchedvertebrates (zone-tailedhawk Buteoalbonotatus), rufigularis), forcarrion.Raptorsof open rivers,lakes, and marshesindude a fishspecialist(the ospreyPandionhaliaetus),two and threespecies snailspecialistkites,a carrion-eating and smallvertebrates, vulture,a Buteothatdiveson arthropods withextremely Snailspecialiststendedto occurirregularly diversediets(e.g.,black-collared hawk,Busarellusnigricollis). thepopulationdynamicsof their duringthe elevenfieldseasonsof thisstudy.Severalraptorsare knownto influence preyspecies.Largeforest-dwelling raptorssuchas theharpyand crestedeaglesarelikelyto requirethelargestpreserves.

RESUMEN y dieta fueronrecopiladaspara las 35 especies Resultadosdel censoy las observaciones de las tacticasde alimentaci6n en 800 hectareas dentrodel ParquenacionalManu, al sudestede Peru.Los resultados de raptores diumosque ocurrieron atravesde una ampliaseriede etapassucesivas. del censoindicanque la mayoriade los raptoresdel bosque ocurrieron de 1 a 2 territorios por 100 hecatarias(ejemplo: Micrastur, Las densidadesde poblaci6nvariaronde un mrnximo en el area total de estudio (ejemplo: aguilas grandes). Harpagus bidentatus),a mucho menos de un territorio donde el L. schistaceaocupa los vallesformados Aparentemente, hayun reemplazode especiesen el generoLeucopternis, mostraronuna por inundaci6ny el L. kublilos terrenos elevadosde bosque (terrafirme).Todos los otroscongeneres considerablesuperposici6nen el uso de la region. de mas de 400 presas transportadas y mas de 200 Basandose en observacioneshechaspor 35 investigadores, Los raptoresdel bosque incluyensiete especiesque ataques, he dividido los raptoresen variosgrupospreliminares. cazan arthropodosy pequeiiosvertebradosdesde perchasescondidas(ejemplo:Micrastur,Leptodoncayanensis);siete especiesque cazan pajarosgrandesy mamiferos, ya sea desde perchasescondidas(Spizaetusornatus),o en ataques a se congregan distanciaenlugaresdondepajaroso mamiferos (Accipiter bicolor);yvariasespeciescondietasespecializadas cachinnans).Las de avispas (Daptrius americanus),caracoles(Chondrohierax uncinatus)y serpientes(Herpetotheres de insectosvoladoresy pequeiios especies que cazan en vuelo induyen cuatro que se alimentanprincipalmente en su percha una que desciendesobrevertebrados vertebrados (Ictinia,Elanoides,Buteobrachyurus y Falco rufigularis); Los raptoresde rios,lagosypantanosinduyenuna especialista (Buteoalbonatatus);y dos Cathartesque buscancarronia. un Buteoque desciende en pescado (Pandionhaliaetus);dos que se especializanen caracoles;uno que come carronia; variadas(Basarellusnigricollis). sobrearthropodos y pequeniosvertebrados; y tresespeciescon dietasextremadamente Las especialistasen caracolesaparecieronmuyirregularmente durantelas once estacionesde esteestudio.Se sabe que varios raptoresinfluencian la dinamica de la poblacion de las especiesde sus victimas.Los raptoresgrandesque habitanel bosque, como Harpia y Morphnus, necesitanlos bosques mas grandes. foragingtactics;guilds;habitatselection. Keywords: AmazonianPeru; diet; diurnalraptors;Falconiformes;

' Received24 March 1993, revisionaccepted 16 December 1993. 443


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ofinterest 1978, Bierregaard1984). The onlymajorstudies organization at thecommunity in theroleof predationin community levelhave beendone by Thiollay and dynamics(Taylor 1984, Martin 1988, Ter- (1989) in FrenchGuiana, who employeda team borgh1988, Ricklefs1989). Predationcan exerta of observersworkingin huge plots (up to 10,000 success,habitat ha) to quantify majorinfluence on thereproductive relativeabundance,habitatselection, selection,populationdynamics,life histories,and home rangesize, and dietsof diurnalraptors,and of the speciesthatmake up a com- the extensivestudiesin southernMexico reported demographies munity(Taylor1984). Martin(1988) hypothesized in Whitacreand Thorstrom(1992). that the availabilityof safe nest sites may limit The purposeofthepresentstudywas to provide Oniki(1979, 1985) and Skutch data comparableto those of Thiollay on habitat speciescoexistence. (1985) havearguedthatnestpredationis important selection,populationdensities,huntingtactics,and in the life historiesof most tropicalforestbirds. diet of Amazonianraptors.In this paper, I have Populationsof one of the commonestspecies of compiledmy observations of raptorsand thoseof Amazonian forestbirds may vary fivefoldin re- 35 otherresearchers workingat the Cocha Cashu (Robinson BiologicalStationin the Manu National Park of sponseto recentattacksbynestpredators how southeastern 1985). Munn(1985, 1986) has demonstrated Perufrom1973 through1989. These of observations predatorsdictatethe structure and organization includesightingsof raptorsattacking thehuge multi-species flockscharacteristic ofmuch preyor carrying foodand all data froman intensive of Amazonia.Terborgh(1988) has further argued censusof the majorhabitatsof the lowlandsector thatlargepredatorsplay a majorrolein regulating of the Manu Park (Terborghet al. 1990). populationsof medium-sizedpredators,whichin turnaffectpopulationsof small preyspecies(Terborgh& Winter1980, Soule et al. 1988). Thus, STUDY AREA AND METHODS even thoughpredatorsmay have low population densities,theylikelyplay a keyrolein community The studysiteis in the 1.5 million-haManu NationalPark in the Departmentof Madre de Dios, organization (Thiollay1989). Peru, at 71?19'W, 11?51'S. Except vulnerable southeastern Evidencethatraptorsare extremely weremade withinan and disturbanceis grow- wherenoted,all observations to habitatfragmentation the Cocha Cashu lack manyforest raptors 800-ha studyarea surrounding ing.Smallforestfragments in both the temperatezone (Robinson 1991) and BiologicalStation.The stationis locatedon an oxin the tropics(Willis 1974, 1979; Leck 1979). bow lake (Cocha Cashu) of the Manu Riverand is Thiollay(1985c) and Whitacreetal. (1992) found 3-4 days by boat fromthe nearestroad. The inthatin disturbedhabitatsforest ofthesitehas protected it fromlogging raptorsarereplaced accessibility of more open habitats. and systematic by species characteristic hunting.For thisreason,the Manu Thiollay(1989) arguedthatlargehomerangesand Park has a full complementof species,induding low populationdensitiesmake raptorsespecially top predatorsand theirprey,at naturalpopulation sensitive to habitatfragmentation, an argument sec- densities. onded by Robinson and Wilcove (1989). Barro Colorado Island, whichhas lost manyof its large MAJORHABITATS.-As the Manu River meanders highlevelsof nest acrossits floodplain,it createsa diversemosaicof raptorsand cats,has extremely predation(Loiselle & Hoppes 1983; K. Sieving, habitats,which have been describedin detail by pers.comm.),perhapsas a resultof thelack of top Terborgh(1983, 1985) and Robinsonetal. (1990) are describedonlybriefly predators,whichpreyon medium-sizedpredators. and consequently here. River:The stretchof habitatalong the Manu Efforts to evaluatetheimpactof fragmentation on raptorsand theimpactof theloss of raptorson Riverindudesopenwater,steeperodedbanks,and have been hamperedby the sandybeachesexposedduringthe dryseason. tropicalcommunities Lakes:The studyareaincludestwooxbowlakes lack of data on raptorecology (Thiollay 1980, 1985a, b, c; Whitacre& Thorstrom1992). The borderedby shrubbymarshesand small trees. Pantanal:A large(> 100 ha) openmarshyarea and inconlow populationdensities, highdiversity, spicuousbehaviorof manyraptorshave made for withscatteredislandsof treesand shrubsand nua veryslow accumulationof basic naturalhistory merousdead treesis locatedin the studyarea. Tessatia/Cane:The firststageof ripariansucof raptorecology data. Most of our understanding comesfromstudiesof singlespecies,especiallyob- cessionconsistsof narrow(< 50 m) beltsof Tesservations at singlenests(e.g., Beebe 1950, Rettig satia, a treelikeplant in the familyCompositae,

THE LAST DECADE HAS SEEN A REEMERGENCE


Ecology of Amazonian Raptors

445

and wider(up to 500 m) beltsof Gynerium, a cane. cicuscela) (Robinson1985) and rivermargins where Plantsseldomexceed 10 m in height. we observedmanyraptorsduringthe2-3 dayboat Transitional forest:The middlestagesof ripar- tripto thestation.All observations notfollowedby ian successionconsistof foreststhatbecome taller initialsare myown. I also compiledthe same data and increasingly diverseas one movesfurther from fromsightings recorded byotherscientists, including theriver.Canopyheightrangesfrom20 m at earlier Dave Bolster(DB), PerriEason (PE), Louise Emstagesof successionto 50 m by laterstages.This mons (LE), John Fitzpatrick(JF), MurrayGellhabitat floods frequently and has an understory Mann (MG-M), Anne Goldizen (AG), Rolando dominatedby Heliconia. Gutierrez (RG), JonHerron(JH), Tom Hildebrand Maturefloodplain forest:This tall,diversefor- (TH), CharlesJanson (CJ),Jennifer Leak (JL),Dave estgrowson highgroundthatseldomfloods.Emer- Lukas(DL), CarolMitchell(CM), Debra Moskovits genttreesreach60 m and the understory is fairly (DM), CharlesA. Munn (CAM), Martha Brecht open exceptaroundtreefalls. Munn(MBM), Ted Parker(TP), Ken Petren(KP), Upland forests:Areas above the currentflood Nina Pierpont(NP), Leonides Quinones (LQ), plainlevelconsistofa mosaicofsteepravines,well- KatherineRenton(KR), David Ricalde(DR), Lily drainedridgetopsand bamboo thickets.These an- Rodriguez(LR), PeterSherman(PS), MargaretSycientforests containnumerousvines,landslides,and mington(MS), JohnTerborgh(JT),GuiselaTesoro treefallgaps. (GT), BettinaTorres(BT), Carelvon Schaik(CV), CarolWalton(CW), Dave Willard(DW), and Pat METHODS.-This paperincludestwo kindsof data: Wright(PW). censusresultsand ad lib observations. Most observations Censuseswere are of raptorscarrying prey conductedin most major habitats,1979-1986. acrossclearings.Capturesof small inconspicuous Census plots and yearswere: matureflood plain preyitems are therefore likelyto be underrepreforest(100 ha, 1982); transitionforest(15 ha, sentedin the data presentedhere. Supplementary 1982; 40 ha, 1984; 60 ha, 1985 and 1986); Tes- dietarydata were obtainedfromspecimensfrom saria/Cane (3 ha, 1982; 5 ha, 1983; 6 ha, 1985 AmazonianPeru depositedin the Louisiana State and 1986); uplandforest(80 ha, 1985 and 1986); University MuseumofNaturalScience(LSUMNS) lake (30 ha, 1979-1985); and river(30 ha, 1982and theFieldMuseumofNaturalHistory(FMNH). 1985). Plotsin forestedareaswerecensusedusing spot-mapmethods(Kendeigh 1944) along trails RESULTS thatwere ?200 m apartin each plot (Terborghet al. 1990). Each trailwas censusedat least20 times ABUNDANCE AND HABITAT SELECTION.-Of the 4 3 fromAugust to November.Lakes were censused Falconiforms (includingvagrantsand Cathartidvulfromcanoesat least20 timesa year.We have not tures)recordedin the lowlandsectorof the Manu systematically censusedpantanalhabitats,butI have National Park, 35 eitherbreedor regularly forage visitedthishabitatfivetimes.Censuseswerecon- in thestudyarea (Table 1). Of theeightremaining ductedby TheodoreA. ParkerIII, JohnTerborgh, species,threearepassagemigrants thatdo not feed in the area (Mississippikite[Ictinia mississippienand ScottRobinson. Our estimatesofpopulationdensitiesarerather sis],Swainson'shawk[Buteoswainsoni],and broadcrudeforraptorswithterritories much largerthan wingedhawk[B. platypterus]), and fivearevagrants ourstudyplots.Forrare,difficult-to-observe species, (i.e., recordedfewerthanfivetimesfrom1979 to I augmentedour censusrecordswithad lib obser- 1989 (turkeyvulture[Cathartesaural, pearl kite vations.Populationdensityestimatesare provided [Gampsonyx hawk [Accipswainsoni],gray-bellied onlyforspeciesknownto resideyear-round in the iterpoliogaster], cranehawk [GeranospizacaerulesCocha Cashu area. Migrantsand vagrants(< 5 cens], and solitaryeagle [Harpyhaliaetussolitarrecords)are treatedseparately. ius]). The orange-breasted falcon(Falco deiroleucus) Ad lib observations wererecordedeach timea has neverbeen recordedwithinthe National Park raptorwas observedattackingor carryinga prey boundariesbut has been observedalongthenearby item.Duringthe41 monthsI spentat theBiological Alto Madre de Dios River (JWF, SR). Vagrants Station(1979-1989), each timeI observeda for- and passage migrantswere exduded fromfurther agingraptorI recordeddate,location,huntingtac- analyses. tics,and diet.My observations werebiasedtowards Populationdensitiesofmostforest-dwelling dilake margins,whereI spentroughly8000 hours urnalraptorsappearedto be low. Onlysevenspecies coloniesoftheyellow-rumped studying cacique(Ca- weresufficiently commonforterritory mappingon


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Robinson

TABLE 1.

Habitat selection and estimated populationdensitiesofraptorsin the Cocha Cashu area. For infrequently observed species,thenumber ofsightings in each habitatis givenin parentheses. Abundanceain each habitatb Species

R

L

Pc

T/C

TF

HGF

UF

King vulture(Sarcorhamphus papa) Black vulture(Coragypsatratus) Turkeyvulture(Cathartesaura) Greateryellow-headedvulture(C. melambrotos) Pearl kite (Gampsonyx swainsonii) AmericanSwallow-tailedkite (Elanoidesforficatus) Gray-headedkite (Leptodoncayanensis) Hook-billedkite (Chondrohierax uncinatus) Double-toothedkite (Harpagusbidentatus) Plumbeouskite (Ictiniaplumbea) Snail kite (Rostrhamus sociabilis) kite (Helicolestes Slender-billed hamatus) Bicoloredhawk (Accipiterbicolor) Gray-belliedhawk (A. poliogaster) Tiny hawk (A. superciliosus) Zone-tailedhawk (Buteoalbonotatus) Short-tailedhawk (B. brachyurus) Roadside hawk (B. magnirostris) Slate-coloredhawk (Leucopternis schistacea) White-browedhawk (L. kubli) Black-collaredhawk (Busarellusnigricollis) Great black-hawk(Buteogallusurubitinga) Crestedeagle (Morphnus guianensis) Harpy eagle (Harpia harpyja) Black-and-white hawk-eagle(Spizasturmelanoleuca) Ornatehawk-eagle(Spizaetusornatus) Black hawk-eagle(S. tyrannus) Osprey(Pandionhaliaetus) Laughingfalcon(Herpetotheres cachinnans) Collaredforest-falcon (Micrastursemitorquatus) Barredforest-falcon (M. ruficollis) Lined forest-falcon (M. gilvicollis) Black caracara(Daptriusater) Red-throatedcaracara(D. americana) Bat falcon(Falco rufigularis)

R U (2) C

R R (1) C

R R

R

R

R

U

U

U

U

U

U R

R R (5) C (1)

Ud

U R

R R

R R

C

C R (1) R

U U (8) U

Cd

Cd

C

Rd

R

U R

R

R

R

R

R

R (1) R

R

R

R

U

U

R R C

R R R

R U

Cd

R C

U (1) (1) R R C R R

C

C

C

C

U U R

R U U R U U

Cd

R

R R C

Ud

R U

R

(1) R

R

R

R (2) (4) R R R

R (6) (11) R R R U U C C

R U

U

U U

Cd

R

U U C

Cd

U

R R

R R

Ud

Cd

C

Ud

Ud

(1) (3) R R R

C

Abundancerankings:C = observedor heardon at leasthalfof censusvisits;U observedor heardonce every310 censusvisits;R = observedor heardless thanonce per 10 censusvisits.Numbersin parentheses referto thetotal numberof observationsforveryrarespecies. b Habitats: R = River; L = Lake; P = Pantanal;T/C = Tessaria/Cane;TF = TransitionalForest;HGF = High Ground Forest;UF = Upland Forest. c Based on only5 censuses. d Nests located. a

thecensusplots,indudingdouble-toothed to detectand maybe muchmorecomkite(three was difficult territories of 50-100 ha each), gray-headedkite mon than our observationssuggest. Harpy and (one territory of 50-80 ha), slate-colored hawk(two crestedeagles,kingvultures,and black-and-white of80-100 ha each),laughingfalcon(one hawk-eaglesappearedto have home rangeslarger territories of 50-80 ha), barredforest-falcon territory (four than the >800-ha area wheremost researchwas territories of40-50 ha each),and linedforest-falconconductedin theCocha Cashu area.Vulturesprob(fourterritories of 40-50 ha each). The restof the ably did not defendterritories, and I saw as many specieseitherhad territories thatweremuchlarger as eightadult kingvulturessimultaneously feeding than 100 ha (e.g., Harpia harpyja)or werestrictly on the same carcass. aerial and therefore difficult to census (threecaSome raptorsthat occurredalong riversand thartid vultures, swallow-tailed kite,plumbeouskite, lakeshad highpopulationdensities.Ospreys,which zone-tailed hawk,short-tailed hawk).The tinyhawk occurredonly as nonbreeders, averaged1-2 indi-



vidualsper oxbow lake (20-50 ha of open water) and also occurredalong the river.Black-collared hawks averagedone pair per oxbow lake. Great black-hawksand blackcaracarasdividedtheirtime betweenthe riverand oxbow lakes and two pairs ofeach speciesoccurredin thestudyarea.Roadside hawksdefended2-4 km stretches along riversand foragedmostlyalongbeachesin Tessatiaand rarely along oxbow lakes. Black vultureswerefoundprimarilyalong the riverand less oftenalong oxbow lakes; theywerecommonlyfoundnearnativesettlements. The threespeciesof snail-eatingkitesoccurred irregularly. Of the 16 recordsof snail kitesfrom 1979 to 1989, 12 wereof juveniles(includingone that residedfortwo monthson a nearbyoxbow lake),threewereofpairs(noneremainedin thearea formorethantwo weeks),and one was of a flock of 14 adultsthatvisitedCocha Cashu foronlyhalf an hour beforeleaving.A group of threeor four hook-billedkiteswas presentin an areaoftransition forestduring1979 and 1980 but was notobserved beforeor againuntil1988 and 1989 whena group of 4 was observedin thepantanal,wheretheyhad not been observedpreviously(C. A. Munn, pers. comm.,S. Robinson,pers.obs.). A pairofslenderbilled kitesmoved intothe pantanalin 1985 and was recordedthroughthe end of the study. The 200-ha pantanalhabitatwas by far the richesthabitatforraptorsin the studyarea. The combination of smallwooded islands,open marshy and nestareas,and isolatedtreesprovidedforaging forall but a few forestinterior ing opportunities The pantanalwas theonlyhabitatwhere specialists. grayhawksand slender-billed kiteswereregularly recorded.The isolatedtreeswere also used by at least eightspeciesof raptorsfornesting,including plumbeous,swallow-tailedand gray-headedkites, roadside hawk, laughingfalcon,black and redthroatedcaracaras,and bat falcons. 2 summarizes data on huntingtacticsand dietsof the 31 species of raptorknownto occurregularlyin the Cocha Cashu area. Below are providedadditionaldetails on the data presentedin Table 2 and the results comparedwiththosefromothersites. ofkingvulturesare Vultures:Our observations consistent withthoseof Houston (1984a, b), who proposedthatthisspecieslocatescarcassesbywatchof Cathartesvultures.Greateryelingtheactivities low-headedvulturessoaredfairlylow (< 100 m) over the canopyand open areas and foundsmall carcassesinsidetheforest(6 observations) and along HUNTING TACTICS AND DIET.-Table

447

watercourses (15 observations feedingon dead fish). King vultures,on theotherhand,soaredveryhigh and aggregatedat largecarcasses,includinga giant armadillo(Priodontes maximus)and a blackcaiman (Melanosuchus niger).Kingvultures supplantedboth black and greateryellow-headedvulturesat carcasses.Black vultureswereconfinedto moreopen habitats,frequently near human settlements, and supplanted greater yellow-headed vultures fromdead fishon at least eightoccasionsalong the edge of Cocha Cashu. Americanswallow-tailed kite:Thisaerialspecies caughta varietyof small insectson the wing (3 2 orthopterans, butterflies, 23 unidentified) and in one instancewas observedhoveringand plucking fruitfroma large canopytree.Publishedreports suggestthatswallow-tailedkitessupplementtheir dietof aerialinsectswithfruit(Buskirk& Lechner 1978, Lemke 1979), nestlingbirdsand otherprey takenfromsurfaces(Skutch 1965, Snyder1974, Lohrer& Lohrer1984). Gray-headedkite: All but two of the dietary observations werefroma paircarrying foodtowards a presumednestthatI neverlocated.Gray-headed kiteswereobservedcarrying 7 lizards(20-40 cm), 2 frogs,one orthopteran, one snake,two lepidopteranlarvae,and one unidentified The vertebrate. seven lizardswere slenderwith long (> 10 cm) tails. The fiveorthoptera were katydids(Tettigoniidae).Theseobservations areconsistent withthose publishedelsewhere (Brown& Amadon 1968:214, Haverschmidt1968:48, Voous 1969, Whitacreet al. 1992). Hook-billedkite:No observations of thisspecies foragingin the Cocha Cashu area weremade. hook-billedkiteseat treesnailsas they Presumably, do elsewhere in theirrange(Smith& Temple 1982, Marroquinet al. 1992). Double-toothedkite:The associationofdoubletoothedkites and primatetroopshas been welldocumented (Greenlaw 1967, Fontaine 1980, Boinski& Scott 1988). In the Cocha Cashu area, double-toothedkites followedtroops of squirrel monkeys(Saimiri sciureus),browncapuchins(Cebus apella), and white-fronted capuchins(C. albifrons),whichflushmanylarge insectsand lizards (Terborgh1983). This specieswas neverobserved of monkeysin the Cocha foragingindependently Cashu area. They were observedeating 13 large insects(2 mothsand 11 orthopterans), and 2 lizards Most ac(one Anolisand one 35-cm unidentified). countsof theirdietalso includeinsects(oftenspecifiedas orthopterans, cicadas,and coleoptera)and smallgreenlizards,includingAnolisspp. Two dou-


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TABLE 2.

Summary ofhuntingtacticsofraptorsin theManu National Park, Peru. Species

Huntingtactics

Black vulture King vulture Greateryellow-headedvulture Swallow-tailedkite Grey-headedkite Double-toothedkite Plumbeouskite Snail kite Slender-billed kite Bicoloredhawk Tiny hawk Zone-tailedhawk Roadside hawk Short-tailed hawk Slate-coloredhawk White-browedhawk Black-collaredhawk Great black-hawk

Crestedeagle Harpy eagle

Black-and-white hawk-eagle Ornatehawk-eagle

Soared low, oftennearhuman settlements Soared veryhigh (> 100 m) Soared 20-50 m overcanopy Soared above canopy,caughtpreyon the winz Short(1-10 m) flightsin upper canopy,shortdives frombranchto branch Followedmonkeytroops,dived on preyflushedby monkeys Soared overopen areas,caughtflying insectsin its talons

Diet Carcasses Largecarcasses Carcasses Insects,fruit Lizards,orthopterans, lepidoptera larvae,frogs,snake,unidentifiable vertebrate Largeinsects,lizards

Lizards,orthopterans, lepidoptera larvae,frogs,snake,unidentified vertebrate Perchedand soaredlow (< 10 m) over Pomaceasnails marshes,dives down to catchsnails One pair observedforagingin shrubs No observations along edge of a marsh Activelyflewbetweenconcentrations of 13 birds, 1 squirrel(Sciurus) treesand birds,especiallyin fruiting along habitatmargins Hunted high in the canopy,possibly No observations followsflocks Soars 50-100 m overopen areas, No successfulattacks,dives at birds dived abruptlyon preybelow it Perchedlow (< 10 m), dived on prey Lizards,insects,snakes along the edges of clearings Soared above canopy,sudden dives on No observations birds Mid-canopyin forestinterior, moth occaLizards,snakes,orthopteran, sionallyfollowedmonkeys,dives to ground Unknown No observations Shallow( 10 nearwatersurfaceor dives down cm) mussels,arthropods, nestling into shallowwater bird Attackednestsof colonialbirdsin Nestlingbirds,eggs,adult birds,frog treesand on beaches,reachedinto marshes,waded in shallowstreams, walked along riverbanks Long flyingattacksthroughdense fo- Squirrelmonkey does not liage in the forestinterior, soar Long flyingattacksthroughdense fo- Howler and squirrelmonkeys,sloth liage in the forestinterior;one attackedacrossa clearing,did not soar Long flyingattacksthroughdense fo- Bird liage and along edges Attackedfromconcealedperchesin Birds,monkeys,rodents,snake canopyand along habitatedges, short(50 m) flyingattacksthrough Squirrel,lizard,rodent forest;stoopeddown at preyin open areas Soars 50-100 m overlake, dived into Fish water Snakes No observations Attackedpreyfroma concealedperch, Spix's guan chased preyin open on long direct flights Attackedfromconcealedperches,often Lizards,katydid low ( 50 m) attacksratherthan ambush preyfrom nearbyconcealedperches.An adult(presumably the same individual)regularly attackeda largeflockof 150-200 Tui parakeets(Brotogeris sanctithomae) thatwas feedingin a Ficus. Each morningforat least 6 consecutivedays,it flewtowardsthe Ficus fromtheeast between0900 and 1030 and chased On the fifthday, it caughtone fleeingBrotogeris. of theparakeets.Anotherattackon a flockof birds feedingin a Cissusvine resultedin the captureof a thrush-sized bird,possiblyTurdusignobilis.Bicoloredhawksattackedyellow-rumped caciquesin a flowering Quararibeatree(apparentlyunsuccessfully),in a fruiting Coussapoa(successfully: JL),and at cacique colonies(all 11 attackswereunsuccessful). A bicoloredhawk was observedchasingan undulatedtinamou(Ctypturellus undulatus)across the Manu River(CW). The hawk caughtits prey as soon as the tinamoureachedthe bank. A bicolored hawk was also observedcatchinga squirrel (Sciurussp.) fromthebole ofa tree(JT). Elsewhere


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hawkshavebeenrecorded Four of thesevenlizardsreportedweresmall (10in itsrange,bicolored birds(Brown& Amadon1968:534, 20 cm) Ameivalizardscaughton the ground.Ineatingmainly hawks dividualscollectedelsewherein Perucontainedthe et al. 1992). Overall,bicolored Quixch'an lizardsand insectparts 13 birds. orcarrying remainsofthreeunidentified wereseencatching hawksregularly(LSUMNS). Groom (1992) found that roadside bicolored Atleasttwojuvenile birdsinthelakebedofCochaCashu.One hawks also consumeeggs and nestlingsof sandattacked lakebedfor colored nighthawks(Chordeilesrupestris)along visitedthesouthern ofthesejuveniles it attacking beachesoftheManu River.Marroquinand Moreno 46 consecutive dayswhenI observed macaws(Arasevera)8 times;yel- (1992) observedroadsidehawkseating15 rats,14 chestnut-fronted or- lizards,8 birds,6 snakes,9 insectsand one frogin caciques13 times;russet-backed low-rumped 23 times;a southernMexico. angustifrons) opendolas(Psarocolius hawk: This specieswas rarelyseen Short-tailed a culminatus), toucan(Ramphastos yellow-ridged (Megarhyncbus flycatcher boat-billed pitangua),a at Cocha Cashu, but has been observeddivingat birdsperchedin the open on the tops martinica), speckled unidentified purplegallinule(Porphyrula chachalacas (Ortalisguttata)4 times;pale-ventedoftreesand attackingswallowsand martins(Progne 5 times;a lettered sp.) overopen water.Elsewhereit attacksa variety cayannensis) pigeons(Columba ani of birds,many of whichare caughton the wing and a greater inscriptus); aracari(Pteroglossus wassuc- (Ogden 1974). T. Parker(pers.comm.)haswatched major).Noneoftheseattacks (Crotophaga hawksin Peruattackingwhite-collared involved tailchasesin which short-tailed cessful. Mostattacks the swifts(Streptoprocne zonaris)in flight. oroutmaneuvered outdistanced thepreyeither escapedby divingreSlate-coloredhawk: This littleknown forest hawk.The purplegallinule thehawkattacked. hawk appearsto have a diet typicalof the genus underwater whenever peatedly (Brown& Amadon 1968:548). Of the al- Leucopternis as practice, Thesechasesmayhavefunctioned fourwereslenjuvenilewas stillbeingfedby an fivelizardsit was observedcarrying, thoughneither derwithlong(> 10 cm) tails(possiblyin thefamily adult. seenhawkseemedto Teidae) and the othermay have been an Anole. Tinyhawk:Thisrarely intheuppercanopyandhasbeen Anotherwas observedcarryinga moth and there exdusively forage a snakeacross aretworecordsofthisspeciescarrying a white-winged shrike-tanager observedcatching inthenearby area a dearing.An individualfollowinga troopof monRioTambopata (Lanioversicolor) A Peru(TAP). A birdcollected just keyscaughtand ate a mothand an orthopteran. of southeastern hawkwas foundperchedon theground con- slate-colored outsidetheManu Park(FMNH) boundary insects ofunidentified tainedtheremains UF). Stiles holdinga frog(CM). White-browedhawk: Thereare no Cocha Cathattinyhawksmaybe hum(1978) suggested shu data on diet or huntingtacticsforthispoorly specialists. mingbird whichbearsa knownspecies.Threebirdsin the collectionat the Zone-tailed hawk:Thisspecies, to Cathartes vultures resemblance (Willis LSUMNS containedtheremainsof an unidentified striking abovecanopyleveland bird,twounidentified lizards,a "smallsnake,"and 1965),soaredat orslightly wereof a beetle. diveddownon prey.Mostof ourrecords onyellow-rumped Black-collared hawk:Thissluggishbirdforaged onbirds,induding three attacks (Tyrannus alongtheedgeofoxbowlakes,whereit caughtprey kingbird caciquesandoneonthetropical Thisspecieswaspresent onlyinfre- fromdisparatetaxonomicgroups,induding11 fish, melancholicus). and during1979-1989,whenitwasobserved 5 snails,4 mussels,4 frogs,3 largearthropods, quently preyincludeda piranha, on 27 of 1200 dayson CochaCashuand9 of 145 a nestlingbird.Identifiable thatit may two Leptodactylus frogs(CC, KP, JL), threelarge lake,whichsuggests dayson a nearby nestlingor fledgling wanderwidely.Brownand Amadon(1968:600) Pomaceasnails,an unidentified a widevariety of (possiblya purplegallinule)(RG, BT), and small and Zimmerman (1976) report smallmam- (50-75 cm) snakes(TP, KP, JL,CC). When catchfrogs, fish, lizards, preyitemsinduding hawksstoopedin a shallow ing fish,black-collared wereofadults. mals,andbirds.All records fromtheManu arc and grabbedfishfromnearthe surface.When Roadsidehawk:Observations withliterature accountsfrom catchinginsects,snails,mussels,snakes,and frogs, area are consistent otherareas(Brown& Amadon1968:574; Hav- black-collaredhawks dived nearlystraightdown beforecarrying & Moreno1992). intoshallowwaterand landedbriefly erschmidt 1968:57;Marroquin preyto a perch.Willard(1985) also describedthe Thisspecies atemosdylargeinsects (3 orthopterans, 2 cicadas)andsmallvertebrates (1 snake,7 lizards). foragingecologyof thisspecies.



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Greatblack-hawk:This raptorused severaldis- attackson primates.Nine attackson primatetroops tacticsthatmade use of itslonglegs. weredocumented(CJ,MS, CM; Eason 1989), sevtinctforaging trees,two of whichresulted Great black-hawksregularlyattackedcoloniesof en at or near fruiting oropen- in thecaptureofsquirrelmonkeys(CS, CJ).In most caciquesand russet-backed yellow-rumped dolas (Robinson1985). Theirlonglegscouldreach cases the harpyflewbelow the top of the canopy nestssuspendedwell below branches.These hawks and maneuveredbetweenthe branchesof canopy usedtheirwingsforsupportwhenreach- treesor along forestedgeswhenapproaching.Two sometimes ing farbelow a perch.From 1979 to 1989 I ob- otherharpieswere observedon the ground,one served39 attackson cacique and oropendolacol- sittingon a red howler(Alouattaseniculus)(Sheronies duringwhich 62 nestlingswere consumed. man 1991) and the otheron a three-toedsloth walked upon open (Bradypusvariegatus)(RG). Eason (1989) obGreat black-hawksfrequently night- serveda glidingattackacrossa clearingon a troop beachesand attackedcoloniesofsand-colored hawks (Groom 1992). I observeda greatblack- of red howlersalong the marginof Cocha Cashu. hawk walkingfromnest to nest in a nighthawk T. Parker(pers.comm.) also has observeda harpy a redhowlerat anothersitein southcolonywhereit ate at least foursmall nestlings. eagle carrying Anothergreatblack-hawkapproachedthe nestof easternPeru. Elsewherein South America,harpy a large-billed tern(Phaetusasimplex)but flewaway eagleshave been recordedtakinga wide varietyof withoutattacking, perhapsbecauseitwas distracted mostlyarborealmammals,especiallysloths(Fowler ofthetern(see alsoGroom & Cope 1964, Rettig1978, Izor 1985) and adult bythemobbingactivities 1992). One hawk carriedthe remainsof a frog male red howlermonkeys(Peres 1990). Black-and-whitehawk-eagle:The only sucwhenit was flushedfroma stream.A birdin the collectionat theLSUMNS containedfishvertebrae cessfulattackobservedwas on a blue-headedparrot capturedat a minerallickwhere and crayfish thatmay have been capturedby birds (Pionusmenstruus) wadingin streams.Greatblack-hawksareregularly hundredsof parrotswerefeeding(LQ). The eagle observedwalkingalong riverbanks, but no prey lunged into a tree and capturedthe parrotas it hawkcaptureshave been observedin this microhabitat. perched.Possiblythesame black-and-white sometimes Greatblack-hawks perchedin low shrubs eaglewas observedat leasteighttimes(CAM, KR) of theminerallick. or in marshgrasswhile searchingforpreybelow attackingparrotsin thevicinity them.Theysometimesused theirwingsforsupport Anotherindividualattackeda group of hoatzins, whilereachingtheirtalonsdeep in the marsh.In- but broke offthe attackafterthe hoatzinit was dividualsforagingin dense shrubshave been ob- chasingcrashedintothe water.A black-and-white hoa- hawk-eaglewas also observedflying througha fruitservedeatingeggsat fivehoatzin(Opisthocomus zin) nests(JP,SR, RG). One greatblack-hawkwas ing fig (Ficus perforata)wherea mixed troop of observedeatingan adulthoatzin(RG) and another squirreland browncapuchinmonkeyswereforaging caught and killed a roadsidehawk that was ha- (CM). The monkeysreactedwithalarmcalls, and theeaglewas unsuccessful. Black-and-white hawkrassingit (TH). Elsewhere,greatblack-hawkstake a varietyof eagles have also been observedattackingcolonies and crested(Psarocoliusoseryi)orvertebrate preyindudingcrabs,snakes,lizards,small of russet-backed mammals,and frogs,as well as occasionallarge opendolas(JL,SR). In each attack,thehawk-eagle insects(Brown& Amadon1968:559, Haverschmidt flewstraighttowardthe nestsand chased females 1968:60, Whitacreet al. 1992) and attackbird as theyleftthe nest.Presumablythe same hawknests(Olmos 1990). eagle was also observedattackingparrotsfromthe hawkCrestedeagle: This rare specieswas observed canopy (KR). Elsewhere,black-and-white birds,smallmammals, fivetimesattackingprimatetroops;one attackre- eaglestakemedium-to-large sultedin thecaptureof a squirrelmonkey(Saimiri and reptiles(Grossman& Hamlet 1964:301). Wilsciureus)(CM). All fiveattacksoccurredat fruiting lis(1988) observedthisspecieshuntingon thewing crest- and divingdownon prey.Our observations suggest treeswheremonkeyswerefeeding.Elsewhere, ed eagles have been recordedtakingbirds(TAP), thatmostattacksoccurfromthecoveroftheforest, observedblack-and-white reptiles,induding snakes, and some mammals althoughwe frequently came hawk-eaglessoaringhighoverthe canopy. (Bierregaard1984). All of our observations Ornate hawk-eagle: This commonesteagle fromprimatologists and undoubtedlybias our data in favorof attackson monkeys. huntedbyperchingin densefoliageand flying horHarpy eagle: As is the case with the crested izontallyor divingdown at nearbyprey. Ornate reflect a probablebiastoward hawk-eagleshave been observedtwicedivingfrom eagle,ourobservations


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caciques(12 atconcealedperchesto thegroundto catchwood-rats observedattackingyellow-rumped caciques,5 on individsp.) (JT,CM), and anotherwas observed tacksobserved,7 on flying (Proecomys oroa rat-sized(20-30 cm) rodent(KR). Or- uals perchedin colonies),and russet-backed carrying In each attack, also havebeenobservedfourtimes pendolas(Psarocoliusangustifrons). natehawk-eagles the divingintoshallowwaterto catchthreepurplegal- the cacique or the oropendolaoutmaneuvered afterbrieftailchasesand escapedinto linules(TAP, CAM, MG-M, SR) and a gray-necked forest-falcon wood-rail(Aramidescajanea) (DM). Afterthreeof densefoliage.In betweenattacks,thecollaredforestin thewater falcon(s)perchedinconspicuously nearcoloniesand theseattacks,theeagle perchedbriefly thepreyintotheforest.One of the waited untilthe caciquesreturned.The onlysucbeforecarrying gallinuleswas stolenby a whitecaiman (Caiman cessfulattackwas on an adultSpix'sguan (Penelope crocodilus) beforetheeagle could carryit back into jacquacu) (CM), whichweighedat least300 g more (S. Robinsonand J. theforest.An ornatehawk-eaglewas also observed thanthe collaredforest-falcon pers.obs.). Observationsat a nest(M. perchedon the groundholdinga 75-cm colubrid Fitzpatrick, snake (RG). Ornate hawk-eagleshave also been Silman, pers. comm.) in the Cocha Cashu area a squirrelmonkey(CS) and two showed a diet consistingprimarily of birds. Elseobservedcarrying have been observed saddle-backedtamarins(Saguinusfuscicollis)(JT, where,collaredforest-falcons at- followingarmyants to catch flushedprey(Mays JWF). I have also observedthreeunsuccessful tackson flocksof oropendolasforagingalong the 1985) and eatingbirds,mammals,lizards,snakes, attackson mixed and insectsoftencapturedas the bird runsalong lakemarginand threeunsuccessful colonies of oropendolasand yellow-rumpedca- the ground(Brown & Amadon 1968:752, Thorattacksincludean stromet al. 1990). Rivera and Cordova (1992) ciques. Additionalunsuccessful pale-wingedtrumpeters foundtheirdiet to indude 35 percentmammals, attackon ground-foraging (Psophia leucoptera)(PS), mixed monkeytroops 27 percentbirds and 15 percentamphibiansin and Aratinga southernMexico. (CJ, CM), Ara macaws, Brotogeris Barredforest-falcon: Even thoughthisspecies parakeetsforagingat a minerallick (CC, KR), and hoatzins(J.P. O'Neill, SR). is verycommon,thereare few observationsof it domesticchickens, Elsewhere,ornatehawk-eaglesappear to eat pri- attackingprey,perhapsbecause barredforest-falin dense understory. marilybirdsand small mammals,and have been cons forageinconspicuously have twicebeen observedforknownto attacklarge cracids(Lyon & Kuhnigk Barredforest-falcons et al. 1992). aging at armyant swarmswhereone captureda 1985, Kleinetal. 1988, Montenegro ThisspeTettigoniidae). Black hawk-eagle:This raptorhas been ob- largekatydid(Orthoptera: a large(30-35 cm) lizardand diving ciesand thelinedforest-falcon servedcarrying (see below)havealso to capturea squirrel been observed attackingunderstorybird flocks suddenlyfromthemid-canopy (Sciurussp.) two m above theground(LR). Black (CAM). AnotherindividualcaughttwoAmeivalizhawk-eagleshave also beenobservedattackingma- ards 15-20 cm long along the edge of a small an un- clearing.The falconperchedinconspicuously twom caws perchedin a tree(KR) and carrying rodent(KR). A largeblack raptor,pos- above the groundbetweenattacks.Barredforestidentified attackedbirdsin mistnets.Four sibly a black hawk-eagle,was observedeating a falconsregularly black-bandedowl (Ciccaba hubula). Elsewhere,it birds collected just outside the National Park has beenobservedeatingbirds,mammals(induding boundary(FMNH) containedtheremainsof three 1980:112, small passerines(possiblya Pipra and two Myrbats),and reptiles(Smith1970, ffrench Funes et al. 1992). motherula antwrens), two smallunidentified mamOsprey:Willard(1985) givesan accountofthe mals, a largegreenbeetle,a nematodehead, and fishselectedbythisspecieson Cocha Cashu. I have miscellaneousinsectparts.Two of the birdsmay seen themcatch41 fishon Cocha Cashu. have been netkillsbecausetheyhad been eatenby were of Laughingfalcon:All 16 observations falconscapturedin mistnets,but the thirdcame snakes25 to unidentified laughingfalconscarrying an from 60 cm in length.No attackson preywereobserved from individualthathad been shot away in mist net lines. A specimen the LSUMNS had it has also beenrecorded forthisspecies.Elsewhere, the remains of a beede. Elsewhere, the barred forest(Skutch lizards,and arthropods eatingsmallrodents, 1960, Brown& Amadon1968:745-746, Guzman falconis knownto eat lizards,slugs,amphibians, and a varietyof arthropods as well as birds(Brown & Orrego 1992). Thisspeciesappearedoc- & Amadon 1968:750, Schwartz1972, Thorstrom Collaredforest-falcon: casionallyin theCocha Cashu lakebed,whereitwas et al. 1992). Remainsat a nestin Guatemala in-



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cludedmostlysmall (< 20 g) birds(Thorstromet before beingsupplanted bya greatyellow-headed al. 1990). are knownto vulture. Elsewhere, blackcaracaras Lined forest-falcon: No observationsof suc- eat arthropods, palm fruits, smallmammals,lizards cessfulattacksby thisspecieshave been recorded, and snakes(Grossman& Hamlet 1964, Brown& althoughit has been observedattackingunderstory Amadon 1968:727). flocks(CAM). An individualcollectedjust outside Bat falcon:This specieswas activeall day and theManu Parkboundarycontainedtheremainsof attacksa widevariety ofaerialpreyinsuddenstoops. a cockroach (Orthoptera: Blattidae)(FMNH). Three At dusk,ithas beenobservedstoopingand catching individualscollectedelsewherein Peru containeda a small (< 10 cm) insectivorous bat and a larger lizard,a Hylid treefrog,insectparts,and the re- Noctiliobat low overthatwater(KP). Bat falcons at bats mainsof a bird(LSUMNS). Elsewhereit has been have been observedstoopingunsuccessfully observed following ants and eating nestlings on 13 occasionsand have been observedcarrying (Schwartz1972). Klein and Bierregaard(1988) foursmall (< 10 cm) and one large (15 cm) bat hypothesize thatlined forest-falcons eat a mixture towarda presumednestsite.Bat falconshave also ofarthropods, lizards,and,occasionally, smallbirds. been observeddivinginto flocksof foragingsandRed-throated caracara:Eventhoughred-throat- colorednighthawkson six occasions(CAM, CC). ed caracaraswerefairlycommon,theonlyforaging These attacksresultedin two captures;one other brokethegripofthefalconand escaped recordis of a group eatingsmall "grubs" froma nighthawk branch(GT); these may have been wasp larvae. beforeit was killed(CAM). Duringtheday,bat falconsattackedinsectsand Elsewhere,red-throated caracaraseat wasp larvae, caterpillars, fruit,and palm seeds (Skutch 1959, birds,especiallyswallows.I have seen bat falcons Brown& Amadon 1968:728). of foragingswallowson stoop into concentrations a successful Black caracara:This conspicuousspecieseats a 27 occasions,butI haveneverwitnessed varietyof preyalong lakes and rivers.Most obser- attack.I have, however,seen bat falconscarrying vationsare of caracarasattackingbirdnests.Black four white-winged(Tacbycinetaalbiventer),one caracarasregularly one blueattackcoloniesofyellow-rumped rough-winged (Stelgidopteryx ruficollis), caciques,wheretheyeat nestlingsand eggs (Rob- and-white(Notiochelidon cyanoleuca),and six uninson1985). Threeattackshave also beenobserved identified swallowsto nestsites.A bat falconwas on thenestsofsocialflycatchers an adultred-cappedcardinal(Pa(Myiozetetes similis) observedcarrying small birds. (KP), but in each case, the flycatchers chased the roaria gularis) and fourunidentified caracarasaway fromnestswithnestlings.Oropen- Bat falconshave also beenrecordedcatching5 buta cicada,and 10 unidentified dolas also chasedblackcaracarasout of colonieson terflies, 3 dragonflies, 12 occasions. largeinsects(SR, CC). Anotherbat falconcaught tree parakeetas it flewinto a fruiting Caracarasalsoregularly attackednestson beach- a Brotogeris es. One familyattackeda colonyof sand-colored along the edge of the river(GT). Bat falconsalso attendedtermite swarms,whereI saw one nighthawks,but caught only one nestlingbefore regularly Duringthreehours leaving,probablyas theresultof the mobbingac- individualcatchover50 termites. tivitiesofpairsofblackskimmers (Rynchops nigra), of observation,a pair of bat falconsfed a recent 26 largeinsects,includingat least 5 butlarge-billed terns(Phaetusasimplex),and pied lap- fledgling 2 cicadas,3 dragonflies, and an orthopteran. wings(Hoploxpterus cayanus).I saw a caracaracar- terflies, Elsewhere,the diet of the bat falconhas been ryingwhat appearedto be a nestlingColumbapibetween thoroughlydocumented(Beebe 1950, Brown & geon.Groom(1992) describesinteractions birdsintheCocha Amadon 1968:824-825, Cade 1982:102-104). blackcaracarasand beach-nesting The Cocha Cashu data are biasedin favorof aerial Cashu area. I have twiceobservedblack caracarascatching detecting aerialcapturesofswallows,which detecting in canopy trees forageoveropen water,and againstdetectingcaplarge (4-7 cm) hairycaterpillars along the lake margin.Two of the six caterpillars turesof forestbirdsand arthropods. caughtweregleanedfromnearbyfoliagebyperched birds.The otherfourweretoo farto reachwithout DISCUSSION flyingand had to be plucked offleaves in short, stallingflights. on thedata RESOURCE DIVISION IN RAPTORS.-Based Black caracarasalso scavengedin campsitesand presentedhere and a reviewof the literature, the nativesettlements, wheretheywereextremely tame. raptorsof thissitecan be dividedintodietarygenA trioofblackcaracarasalso ate partof a dead fish eralists thateatpreyfromseveraltaxaand specialists


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TABLE 3.

A preliminary guild classification oftheforest-dwelling raptorsoftheCocha Cashu area.

Huntingtactics Aerialsearching

Prey Flyinginsects,preyon surfacesof trees Small vertebrates, and largeinsects Carrion

Attacksfromperches

Small vertebrates, largearthropods

Snails Wasps Birds,mammals Snakes Aquatic animals Long (>50 m) attacks

Birds,occasionallymammals Mammals and lizards;occasionally birds

Species Swallow-tailedkite Plumbeouskite Bat falcon Short-tailed hawk King vulture Greateryellow-headedvulture Canopy Grey-headedkite Double-toothedkite (with monkeys) Tiny hawk Bat falcon(openings) Understory Slate-coloredhawk (floodplain) White-browedhawk (upland) Lined forest-falcon Barredforest-falcon Hook-billedkite Red-throatedcaracara Ornatehawk-eagle Collaredforest-falcon Laughingfalcon Black-collaredhawk Bicoloredhawk Black-and-white hawk-eagle(?) Collaredforest-falcon Black hawk-eagle Crestedeagle Harpy eagle

thatcatchpreyprimarily froma singletaxon.Spe- prey,zone-tailedand short-tailed hawks,bat falcon cialistsindude thethreesnail-eating and black kites,thefish- and, occasionally,the black-and-white eatingosprey,the carrion-eating vultures,the two hawk-eagles.Species that searchfromperchesinmostlyinsectivorous aerial kites (plumbeous and clude double-toothed,slender-billed,and grayand black-colswallow-tailed), thebird-eating bicoloredhawk,the headedkites,roadside,slate-colored, snake-eatinglaughing falcon and, possibly,the laredhawks,greatblack-hawks, collared,lined,and mammal-eating harpyeagle. Dietarygeneralists bat falcons(occasionally)and in- barredforest-falcons, dude speciesthateat a mixtureof arthropods and ornatehawk-eagles.Harpy and crestedeaglesmay small vertebrates(e.g., gray-headedand double- bothperchinconspicuously whilesearchingforreltoothed kites,roadside and slate-coloredhawks, ativelyimmobilepreysuchas slothsand lizardsand barredand linedforest-falcons, black caracara,bat make long-range(> 50 m) attackson treeswhere falcon),andthosewithextremely diversediets(black- monkeysand birdsaggregate(Eason 1989). Simcollaredhawk,greatblack-hawk,crestedeagle,or- ilarly,bicoloredhawks may traplinefruitingand nate,hawk-eagle, collaredforest-falcon). treesand attackwhateveris thereat the Zone-tailed, flowering short-tailed, and tinyhawks and black-and-white time.Black-and-white and ornatehawk-eaglesalso hawk-eaglesmay specializeon birds,but thereare wereobservedattackingpreyfromdistancesof at too fewdata fromthe Manu to classifythem. least 100 m. Attacksof forest-dwelling raptors, Raptorscan also be divided into speciesthat however,wererarelyobservedfromstartto finish. primarily searchon thewing,thosethatsearchfrom The foraging tacticsusedbythelargereaglesremain perches,and those that at least sometimesmake largelya matterof speculation(Rettig1978). longflights throughtheforest to attackprey.Species on huntingtacticsand Combininginformation thathuntprimarily on the wing includethe four diet,severalguilds of raptorscan be distinguished vultures,swallow-tailedand plumbeouskites,os- (Table 3). The threeguildsofaerialforagers consist



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forage ofsix speciesthatsearchforpreyabove thecanopy. sized birds;whereas,collaredforest-falcons and have been observed hawksappear to have morein the forestinterior Bat falconsand short-tailed overlappingdiets with both species takingsmall attackingbirdsas largeas the Spix's guan (1200smaller 1300 g; S. Robinson,pers. obs.). Collaredforestbirds.Bat falcons,however,areconsiderably foragealongtheedge on insectsand crepuscular falcons,however,occasionally and forageextensively Swal- of the forestand attackthe same kindsof preyas nighthawk). batsand birds(e.g.,sand-colored low-tailedand plumbeouskitesboth catchinsects the bicoloredhawk. In Mexico,collaredforest-falbutterflies, cons also ate manymammals(Rivera & Cordova on the wing and eat large dragonflies, kitesfor- 1992). In general,swallow-tailed and orthoptera. Too littleis knownof the diets and hunting age more over the forestthan plumbeous kites, hawk-eagles differ tacticsof black and black-and-white openings.The twocarrion-eaters whichprefer forcomparisonwithornatehawk-eagles.All three in the size of the carcassestheyeat. among speciesattacksmallmammalsand largebirds.Black A fewsubgroupscan be distinguished more lizardsand the sevenspeciesthatsearchforsmall vertebrates hawk-eaglesmay take relatively and insectsfromconcealedperches(Table 3). Dou- rodents(Sciuridae)(Funes et al. 1992); whereas, more hawk-eaglesmayconcentrate ble-toothedkitesfollowprimatetroopsalmostex- black-and-white dusively,usuallyin the mid-canopy.Grey-headed on attackingbirds.Ornatehawk-eagles,however, generalizedin theirdiet (Klein et al. kitesforagemore in the upper canopyand catch are extremely largerlizards and frogsand fewerinsects.Slate- 1988) and seem to overlapbroadlywiththe other coloredhawksforagelowerthanthedouble-toothed two hawk-eaglesand the collaredforest-falcon. kites(T. A. Parker,pers.comm.) and takeconsiderablylargerpreyand fewerinsects.The whiteslate-colored IMPACTSOF RAPTORSON PREY POPULATIONS.-All rapbrowedhawk replacesthe congeneric thoughlittleis knownof torsprobablyhave majorimpactson at leastsome hawk in upland forests, itsdiet.The tinyhawkmaybe a specialiston small of theirprey,but onlya fewcases are well-docubirds,but too littleis knownofitsdietin theManu mented.The tightclusteringof nests in yellowforagemorein rumpedcacique coloniesappearsto resultat least it. The two forest-falcons to classify thanotherguild members.In in part because it improvesdefenseagainstblack theforestunderstory to youn- caracaras(Robinson1985). The caciquepopulation arerestricted general,barredforest-falcons largeare oftheCocha Cashuareavariesalmosttenfold, ger floodplain forest,and lined forest-falcons (terra lyin responseto thesuccessor failureofrecentgreat foundin olderfloodplainand uplandforests 1988). Theirterritories,black-hawkattackson colonies(S. Robinson1985, firma)(Klein& Bierregaard however,overlapbroadlyin maturefloodplainfor- pers.obs.). During 1980-1985 whengreatblackcaciqueswerethe hawk attackswereunsuccessful, ests(Terborghet al. 1990). and mostabundantbirdin theCocha Cashu area(RobSpecies that searchfor small vertebrates insectsfromconcealedperches(e.g., forest-falcons)inson 1985, Terborghet al. 1990). Since 1985, tendto be themostabundantdiurnalraptors.These however,all large(> 40 nest) colonieshave been hawks exploitfood at lower trophiclevels where destroyedby greatblack-hawksand the regional more food is likelyto be available. Raptors(e.g., populationhas droppedbyan averageof75 percent much (S. Robinson,pers.obs.). Terborgh(1983, 1988) eagles)thateatlargerpreyarecorrespondingly that the social organizationand has hypothesized less abundant. The sevenspeciesthatattacklargervertebrates possiblythepopulationdynamicsof mostprimates byraptorpredation.Frequentpredfromwithinthe forestcanopyhave poorlyknown aredetermined foragingecologies.Crestedeagles appear to forage ator attacksby hawk-eagleson parrotsappear to at a minerallick(C. Munn, patterns 1984), dictateforaging (Bierregaard onlargereptiles moreextensively at Cocha Cashu was pers. comm.). Munn (1985, 1986) also hypothebut the onlypreyobservation a squirrelmonkey.Harpy eagles forageon large sized that raptorpredationdictatesthe social orflocksthatdominate mammals(up to thesizeofhowlermonkeys)(Eason ganizationofthemulti-species birdcommunities. and understory forest the canopy also take but Sherman 1991), Peres 1990, 1989, iguanas and even bird nests (E. Alvarez, pers. Social foragingin sand-colorednighthawksand and bicolored swallowsmay largelyfunctionin defenseagainst comm.). Both collaredforest-falcons somewhatin habitat bat falcons.Severalspecies,includingcaciquesand hawksattackbirds,but differ selectionand the size of preyattacked.Bicolored oropendolas(S. Robinson,pers. obs.) and beachfrommulbirds(Groom 1992), maybenefit hawks preferhabitatedges and attack medium- nesting


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associations becausetheyimprove ti-species nesting defense againstraptors.

C. Sanderson,and C. Mitchellread the manuscriptand provided many helpfulcommentsas well as data. E. Alvarezand R. Kennedyprovidedusefulcommentson the manuscriptand broughtseveralkeyreferences to my attention.As always,we are gratefulto the Peruvian ACKNOWLEDGMENTS Ministeriode Agricultura, DireccionGeneralForestaly I thankthe manypeople listed in the methodssection Fauna fortheircontinuedpermissionto workin thePark. forprovidingme withunpublishedsightingsof raptors. My fieldwork was fundedby the Frank M. Chapman Without theirhelp, this paper would not have been MemorialFund, the Societyof Sigma Xi, the National the dietsof raptorselsewhere ScienceFoundation,and theIllinoisNaturalHistorySurpossible.B. Iko researched vey.This paperis dedicatedto thememoryofTed Parker. in theirrange.C. A. Janson,C. Munn,J. Terborgh,G.

LITERATURECITED BEEBE, W. BEISSINGER,

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