DECEMBER 1997 SHORT COMMUNICATIONS 385 gration and wintering location for American Kestrels, tance and companionship during an unusually wet peri- particularlyfor female andjuvenile (del Hoyo et al. od on Socorro. 1994). The sizes of the two winter territories I observed LITERATURE CITED (3 and 6-8 ha) were small compared to those observed in the northern U.S. (Craighead & Craighead 1969, En- BALGOOYEN,T.G. 1976. Behavior and ecology of the derson 1960, Mills 1975). In California, Cade (1955) ob- American Kestrel (Falcosparverius L.) in the Sierra Ne- servedsimilarly small winter territories (e.g., a vacantlot vada of California. Univ. Calif.Publ. Zool. 103:1-87. 100 X 130 m in size). It may be that Mediterranean-type CAOE,T.J. 1955. Experiments on winter territoriality of and tropical winter habitatswith their mild or warm cli- the AmericanKestrel, Falco sparverius. Wilson Bull. 67: matesoffer higher densitiesof prey biomassfor wintering 5-17. kestrels than do habitats in temperate and boreal cli- CRAIGHEAD,JJ. AND F.C. CRAIGHEAD,JR. 1969. , mates. and wildlife. Dover Publishers, New York, NY U.S.A. RESUMEN.--Y observe lo minimo de 14 diferente Falco DELHOYO, J., A. ELLIOTTAND J. SARG^TAL[EDS.]. 1994. sparveriusen la isla de Socorroen el pacificode M6xico Handbook of the birds of the world. Vol. 2. Lynx Ed- en 1992. Los Falcosparverius parecieron ocupar y defend- icions, Barcelona, Spain. er territorios de presa en areasherbosas en la isla donde ENDEaSON,J.H. 1960. A population studyof the sparrow primeramente cazaban grillos, saltamontesy langostas. in east-central Illinois. Wilson Bull. 72:222-231. Estosterritorios de cazar varian en tamafio de 3-8 ha y MILLS,G.S. 1975. A winterpopulation study of the Amer- estabannotable maspequenos que esoantes descubridos ican Kestrel in central Ohio. Wilson Bull. 87:241-247. para Falcosparverius. VARLAND, D.E., E.E. KLA• AND T.M. LOUGHIN. 1993. Use [Traducci6n de Rafil De La Garza, Jr.] of habitat perches, causesof mortality and time unul dispersal in post-fledging American Kestrels.J. Fzeld ACKNOWLEDGMENTS Ornithol. 64:169-178. Funding for the stayon Socorro Island was provided WEHTJE,W., H.S. WALTER,R. RODRIGUEZ-ESTRELLA,J. LLI- by UCLA's Latin AmericanCenter, a UC Mexusresearch NAS AND A. CASTELLANOS-VERA. 1993. An annotated grant and by CIBNOR in La Paz through a grant from checklist of the birds of Isla Socorro, . West. the World Wildlife Fund (USA) for the binational Socor- Birds 24:1-16. ro Island RestorationProject (SIRP). I thank the Mexi- can Navyfor logisticsupport and my researchcolleagues, particularly Ricardo Rodriguez-Estrella,for their assis- Received12 December1996; accepted14 August1997

J. RaptorRes. 31 (4) :385-387 ¸ 1997 The Raptor ResearchFoundation, Inc.

DIET OF THE SPECTACLEDOWL (PULSATRIXPERSPICILLATA)DURING THE RAINYSEASON IN NORTHERN OAXACA, MEXICO

HI•CTOR GOMEZ DE SILVA Institutode Ecologia, UNAM, ApartadoPostal 70-275, CiudadUniversitaria, UNAM, C.P 04510, Mdxico,D.F.., Mexico

MONICA PI•REZ-VILLAFA•A Calle1537-3, Col.San Juan deAragOn, Secci•n 6, C.P 07918, Mgxico,D.F.., Mexico

Jos•, ANTONIOSANTOS-MORENO Departamentode Zoologfa,Instituto de Biologia, Apartado Postal 70-153, UNAM, C.P 04510 Mgxico,D.F., Mexico

KEYWORDS: SpectacledOwl; perspicillata; naked- 750 g in mass(Stiles and Skutch1989). Basedon its size, tailedclimbing-rat; Tylomys nudicaudus; diet;, Oaxaca, Mex- it is likely that it preys on the largest potential prey spe- ico;niche segregation. cies in tropical forests (Emerson et al. 1994) and it is known take mammalsup to the sizeof (Dasyprocta The SpectacledOwl (Pulsatrixperspicillata) is the largest spp.), (Mephitinae) and (Didelphi- in humid tropicalforests of the NewWorld, averaging dae). It alsopreys on birds aslarge as (Psar- 386 SHORT COMMUNICATIONS VOL. 31, NO. 4

Table 1. Prey remains identified in 19 pellets of the the only evidenceof birds wasfeathers in one pellet and Spectacled Owl (Pulsatrixperspicillata) in northern Oa- isolatedbone fragmentsin others.Arthropods were rep- xaca, Mexico. Numbers represent conservativeestimates resentedby varied, usuallysmall fragments of mandibles, of the number of individualscontained in the sample. elyter fragments, cephalic ornaments and valvesof fe- male tettigonids.No arthropod remains were found in NO. OF the last sevenpellets we collected but they were found in INDMDUALS the 12 previouslycollected pellets. Becauseof this, we TAXON I• S•v•m• feel certain that prey other than and opossums were underrepresentedin our sample. : Our most noteworthy finding was that at least 20 and Tylomysnudicaudus 20 maybeas many as 24 prey items (75-80% of the individ- Marmosasp. 4 uals) belonged to one speciesof , the naked-tailed Small rodent 2 climbing rat (Tylomysnudicaudus). Nine rodent and two Unidentified 4 opossumspecies were found during preliminary surveys Chiroptera 1 of the area (Ch•tvezTapia et al. 1993). They ranged in massfrom 17-4000 g but 63.6% of them weighed <200 Birds: g. The naked-tailed climbing rat is semiarborealand is Momotus momota 1 the largestnocturnal rodent in the area. Its mean adult Leptotilasp. 1 massranges from 156-326 g (Emmons 1990). Unidentified 2 Owls usually swallowtheir prey whole and therefore Arthropods: rarely consume prey larger than themselves(Bowles Melanototusglobosus (Tettigonidae, Pseu- 1916; Marti 1974). The naked-tailedclimbing rat wasthe dophyllinae) 3 largest nocturnal found in the area that is small- Ericlusspiniger (Tettigonidae, Copiphor- er than the SpectacledOwl itself.Crustacean remains in inae) 1 pellets suggestedthat the owl wandered at least as far as Golofasp. (Scarabaeidae,Melolonthi- the nearestpermanent streamapproximately 700 m away dae) 1 to forage, and remains suggestedforaging also oc- curred at the mouth of a cave that was located about 750 Cetinissubviolaceus (Scarabaeidae, Cetin- inae) 1 m from the roost. Owls preying on usuallydo so at Unidentified, scarabaeid 1 duskwhen the bats leave cavesin large numbers (Twente Tenebrionidae 2 1954, Baker 1962). The owl roost was only 400 m from Small crustacean 2 the edge of a large man-made clearing that was largely abandonedand overgrownwith tall grassesand reeds.It is interesting that the pellets did not contain remains of ocoliusspp.) andjays (Corvidae),and large ,lizards small mammals typical of clearingssuch as the abundant andfreshwater crustaceans (/•lvarez del Toro 1980,Stiles cotton rat (Sig'modonhispidus), which apparentlybreeds and Skutch 1989, Sick 1993). year round in the studyarea (Ch/tvezTapia et al. 1993). While conducting fieldwork during the rainy seasonin In , the Spectacled Owl has been found to 1994 near Cerro de Oro, Oaxaca (18ø02'N, 96ø15'W),we hunt at forest edges and clearings (Stiles and Skutch found an owl roost where we observed an adult Specta- 1989). It would be inefficient for a large owl, such as the cled Owl for severaldays. We collected 19 fresh pellets SpectacledOwl, to capture small prey unlessthey could from beneath the roost site from 19 July-24 September. be caughtvery easily and quickly(Marti 1974) sincesmall Here, we report the contentsof these pellets (Table 1), prey would make food availableat a slowerrate relative becausefew quantitativedata have been published on the to the time and energy expended capturing them diet of this species.Cerro de Oro is very close to the (Brown et al. 1993). northern limit of the SpectacledOwl's range (Howell Naked-tailed climbing rats could alsobe the preferred and Webb 1995) and this region hasfewer potential prey prey elsewhere in the species' range. Adults of naked- speciesthan at other siteswhere the diet has been stud- tailed climbing-ratsare probablytoo large for other rain- led. forest owls to capture. If this is true, it suggeststhat co- Our samplewas somewhat biased since it waslikely that existenceof SpectacledOwls with severalowl speciesmay not all prey consumedby the owl was regurgitated,and be facilitated by their concentrationon prey speciesun- not every item that wasregurgitated was identified. Also, availableto other owls (Wilson 1975). some typesof prey were more likely to be found in pellets than others. For example, numerous mandibles and oth- RESUMEN.--Seestudia la dieta del Bfiho GorjiblancoPul- er parts of rodents and opossumswere found in pellets satrixperspicillata mediante la identificaci6n de los restos but the only evidenceof a bat wasa phalanx and a single de sus presascontenidos en egrag6pilasque recogimos tooth in separatepellets found on the sameday. Similarly, in Cerro de Oro, Oaxaca, durante la 6pocade 11uvias.La DECEMBER 1997 SHORT COMMUNICATIONS 387 presa m•tsfrecuente que se identific6 en las egagr6pilas lution of body size:consequences of an energetic def- es Tylomysnudicaudus, una rata grande semiarb6rea. inition of fitness. Am. Nat. 142:573-584. Otras presas incluyen insectosde diferentes tamafios, CHAVEZ TAPIA, C., L. ESPINOZA,A. DESUCRE, P. RAMIREZ, mamiferos medianosy pequefios (incluyendo un murciO- F. LOPEZMARTINEZ, V. CORTES,N. CASTILLO,V. QUIN- Iago), avesmedianas y probablementecrusfftceos. La pre- TANA,P. GUZMAN,A. VAZQUEZ,C. CHAVEZ2•ND J F sa principal probablemente es demasiadogrande para MACiAS. 1993. Estudio mastofaunistico de Cerro de que se alimenten de ella los otros bfihosque se encuen- Oro, Tuxtepec, Oaxaca. Memorias XVII Simposiode tran en la mayor parte del •trea de distribuci6n del Bfiho Biologiasde Campo y X Coloquio EstudiantilTercera Gorjiblanco. Etapa. UNAM CampusIztacala MOxico,D.E, Mexico. EMERSON, S.B., H.W. GREENE 2•ND E.L. CHARNOV. 1994. ACKNOWLEDGMENTS Allometric aspects of predator-prey interactions. The mammalremains were identified by the third author, Pages 123-139 in P.C. Wainwright and S.M. Reilly the insectremains by GuillerminaOrtega (tettigonids)and [EDS.],Ecological morphology: integrative organismal Santiago Zaragoza (Coleoptera), and the possiblecrusta- biology.Univ. Chicago Press,Chicago, IL U.S.A. cean remainsby Jos6Luis Villalobos,all from the Instituto EMMONS,L.H. 1990. Neotropical rainforest mammals' a de Biologia,UNAM, Mexico City. remainswere iden- field guide. Univ. Chicago Press,Chicago, IL U.S.A. ufied by the first author with the help of Adolfo Navarro HOWELL,S.N.G. 2•NDS. WEBB.1995. A guide to the birds and EsperanzaAlvarez Mondrag6n, using the referencecol- of Mexico and northern . Oxford lection of the Museo de Zoologia, Facultad de Ciencias, Univ. Press, Oxford, UI• UNAM. We are grateful to Tizoc Altarniranoof the Museo MARTI,C.D. 1974. Feeding ecologyof four sympamc de Zoologia,UNAM•Campus Iztacala,for partial support owls. Condor 76:45-61. of our fieldworkin Cerro de Oro. DalcioDacol helped find informationon the diet of thisspecies. SICK, H. 1993. Birds in . Princeton Univ. Press, Princeton, NJ U.S.A. LITERATURE CITED STILES,F.G. 2•NDA.F. SKUTCH.1989. A guide to the birds of Costa Rica. Comstock/Cornell Univ. Press, Ithaca, •tLVAREZDEL TORO, M. 1980.Las Aves de Chiapas,2nd NY U.S.A. ed. UniversidadAut6noma de Chiapas,Mexico. TWENTE,J.W. 1954. Predation on batsby hawksand owls. BAI•R, J.I• 1962. The manner and efficiency of raptor Wilson Bull. 66:135-136. depredationson bats. Condor64:500-504. WILSON,D.S. 1975. The adequacyof body sizeas a niche BOWLES,J.H. 1916. Notes on the feeding habits of the difference. Am. Nat. 109:769-784. Dusky Horned Owl. Oologist33:151-152. BROWN,J.H., P.A. MARQUETAND M.L. TAPER.1993. Evo- Received13 October 1996; accepted24July 1997.

J. RaptorRes. 31 (4):387-389 ¸ 1997 The Raptor ResearchFoundation, Inc.

NOTES ON A NEST OF THE TAWNYFISH-OWL (KETUPAFLAVIPES) AT SAKATANGSTY, T•dw•'q

YUAN-HSUN SUN I Departmentof Wildlifeand Fisheries Sciences, Texas A &M University,College Station, TX 77843 U.S.A.

YING WANG Departmentof Biology,National TaiwanNormal University,Taipei, Taiwan 117

KEITH A. ARNOLD Departmentof Wildlifeand FisheriesSciences, Texas A&M University,College Station, TX 77843 U.S.A.

KEY WORDS: TawnyFish-Owl; Ketupa flavipes; breeding; parts of Ospreys(Pandion haliaetus), fish-eagles (Ichthy- Taiwan ophagaspp.) and sea-eagles(Haliaeetus spp.). There are four speciesin the Asian genusKetupa and three species Fish-owlsare often regarded as the nocturnal counter- in the African genus Scotopelia(Fogden 1973). Of the Asian species,we know the least about the Tawny Fish- Owl (Ketupafiavipes).Kou (1986) reported one instance • Present address: Department of Forest Resource of mating on Taiwan and Voous (1988) described nest Management and Technology,National Pingtung Poly- locations and clutch sizes in India. Herein, we document technic Institute, Pingtung, Taiwan 902. the diet of a pair of TawnyFish-Owls and attempt to dem-