RaptorP•. 36(4):332-334 2002 The Raptor Research Foundation, Inc. DIET OF BREEDINGTROPICAL SCREECH-OWLS(OTUS CHOLIBA)IN SOUTHEASTERNBRAZIL jOSl• CARLOSMOTTA-JUNIOR 1 Departamentode Ecolo,•a, Instituto de Bioci•nciasda Universidadede SdoPaulo, 05508-900, SdoPaulo, SP,Brazil KEYWORDS: Trt•fical Screech-Owl;Otus choliba; breeding in the pellets. Both prey remains and the reference col- dzet;prey biomass; Brazil. lection were depositedat the Departamento de Ecologia, Universidade de S5o Paulo, Brazil. The Tropical Screech-Owl (Otus choliba)occurs east of RESULTS AND I)ISCUSSION the Andes Mountains fi•om Costa Rica to Uruguay and northern Argentina, and is also found throughout much All three nestswere in cavitieslocated at a height of of Brazil (Meyer de Schauensee1966, Burton 1992, Sick 1.0-1.5 m in dead Eucalyptussp. tree trunks, presumably 1993). It is one of the most common and widespread made by woodpeckersoriginally. Smith (1983) pointed neotropical owl species inhabiting forest edges, open out that Tropical Screech-Owlnests are typicallylocated woodlands, savannas, and other habitats with some ar- in tree cavities.In spite of the monthly field excursions boreal cover,including urban areas (Sick 1993, del Hoyo to the study area during 1992-93, nestswere only found et al. 1999). Despite its commonnessand widespreaddis- on 25 November 1992 (Nest 1, with one t•male and three tnbution, little ecologicalinformation is availableon this owlets), 28 October 1993 (Nest 2, with one female and species,except for some data concerning natural history two owlets), and 6 November 1993 (Nest 3, with one fe- and breeding (Thomas 1977, Smith 1983). Food habits male and three owletas).The three adult females inside have been described only qualitatively (e.g., Thomas cavitieswere captured by hand and weighed with a spring 1977, Smith 1983, Gallardo and Gallardo 1984). Here, I scale.The mean and standarddeviation of body masswas provide more detailed information about the diets of 128.3 -+ 11.7 g. Subsequently,the adultswere placedback nestling and adult Tropical Screech-Owlsduring the into the cavities.Prey remains were collected the first breeding season.Data on nest locations and the timing time the nest wasfound and shortly after owletsfledged. of reproduction in southeasternBrazil are also present- Analysisof pellets and pellet debris revealed at least 34 ed speciesof prey consumed. Invertebrates, mostly oftholY terans such as Lutosa brasiliensis,were most frequent in STUDY AREA AND METHODS the diet (Table 1). Spiders (Lycosidea) and ants (For- The s!udy wasconducted at Ch•tcaraMattos/Faber-Gas- micidea) were also important numerically. In terms of tell (21ø59'S,47ø56'W), located I km westof the city of biomass,invertebrates also prevail, however, the few ver- S•to Carlos, S5o Paulo State, Brazil. The 90 ha studyarea tebrates found, represented a third of the consumedbio- consistsprimarily of Pinusspp. plantationswith some sec- mass (Table 1). ondary-grasslandsavanna. A small patch (3 ha) of dis- The mean body massof prey consumed by Tropical lurbed gallery forest also occursin this area. The land- Screech-OMswas 0.93 _+2.35 g, ranging from 0.02-28.80 scape surrounding the study area is sugar cane plantations and the outskirts of' the city of S•to Carlos. g (N = 309 prey items). Most prey (73.5%) weighedbe- The climate is a transition between K6ppens'sCwai and tween 0.1-1.0 g. Aw•, or rainy tropical with a wet (October-March) and a Tropical Screech-Owlsonly were observed foraging at dry (April-September) season(Tolentino 1967). night. On two occasions,an individual wasobserved leav- Four samplesof pellet debris (represenling ca. 30 pel- ing a perch on a tree and, in flight, capturing insectson lets) and six complete pellets were collecled from three the leaves of another tree. On another occasion, an in- occupiednest cavities.This material waswashed through dividual left a perch on a bush and captured an uniden- a line mesh screen (0.2 mm) and oven-dried (50øC) [br tified invertebrate on the ground. Gallardo and Gallardo 24 hr for storage and analysis.Prey remains were identi- (1984) reported a similar behavior in Tropical Screech- bed by comparison with a reference collection made Owls. I have observed these screech-oMscatching insects trom material from the study.I also measuredthe mass ol prey ilems collected from the sludy area. Individuals in flight, particularly in the vicinity of artificial light m the prey remains were counted by pairing mandibles, sources,which was also reporled by Smith (1983) and w•lh ihe exception of beetles and ants, which were count- Sick (1993). During the period of activity (1800-0600 H) ed by Ihc number of heads,and scorpionsby the number owlswere observedon percheswaiting for potential prey; of slings. The analyzed prey remains presumablywere therefbre, this speciesprobably should be classifiedas a [rom owletsand possiblyadults. I also assumedthai ver- "sit-and-wait"forager, which is typical for the genus Otus leb•atc prey were entirely ingestedlike invertebrales,be- (Jaksic and Carothers 1985). cause crania and other body bones were alwayspresent The qualitative studiesof Thomas (1977) and Smith (1983) indicated that the diet of Tropical Screech-Owls E-mail address:[email protected] consistedmostly of insectsin GostaRica and both insects 332 DECEMBER 2002 SHORT COMMUNICATIONS 333 Table 1. Prey items found in pellets and pellet debris of Tropical Screech-Owlsin southeasternBrazil, with their percentagesin relationto total number and estimatedbiomass (g). Activityperiods and sitesof preywere determined based on field observationsand information provided by Manoel M. Dias (pets. comm.). PERCENT PFRCFNT PREY ITEMS ACTIVITY PERIOD ACTIVITY SITE NUMBER BIOMASS Rodents Bolomyslasiurus Nocturnal/crepuscular, Ground 0.3 10.1 Diurnal Calomystener Nocturnal/crepuscular Ground 0.3 3.6 Oligm•zomysnigripes Nocturnal/crepuscular Foliage/branches, 0.3 6.0 Ground Opossums Gracilinanussp. Nocturnal/crepuscular Foliage/branches, 0.3 5.7 Ground Snakes Unidentified small sp. ? ? 0.3 3.3 Amphibians Hylidae (unidentified sp.) Nocturnal/crepuscular Foliage/branches 0.3 5.3 SUBTOTAL VERTEBRATES -- -- 1.9 34.1 Scorpions Bothriurusspp. Nocturnal/crepuscular Ground 3.6 1.0 Tityiusbahiensis Nocturnal/crepuscular Ground 0.3 0.1 Spiders Lycosidae (unidentified sp.) Nocturnal/crepuscular Ground 11.3 5.9 Unidentified spp. ? ? 1.3 0.8 Harvestmen Opiliones (unidentified sp.) ? ? 0.3 0.1 Insects Blattidae (Parah0,vneticasp.) N octurnal/crepuscular Ground 1.6 3.2 Blattidae (unidentified sp.) ? ? 0.3 0.2 Termitidae (workers) Nocturnal/crepuscular, Ground 2.6 0.2 Diurnal Acrididae spp. Diurnal Foliage/branches 2.9 1.4 Tettigoniidae (Copiphorinae) Nocturnal/crepuscular Foliage/branches 5.8 6.0 Tettigoniidae (Conocephalinae) Nocturnal/crepuscular Foliage/branches 0.6 0.2 Gryllacrididae ( Lutosabrasiliensis) Nocturnal/crepuscular Ground 41.1 34.2 Gryllidae Nocmrnal/crepuscular Ground 1.6 1.6 Unidentified Orthoptera ? ? 0.6 0.3 Mantidae Nocturnal/crepuscular Foliage/branches 4.2 2.8 Carabidae (small unidentified spp.) Nocturnal/crepuscular Ground 1.0 0.1 Scarabaeidae (Rutelinae) Nocturn al/crepuscular Foliage/branches 0.3 0.3 Scarabaeidae (Dynastinae) Nocturnal/crepuscular Ground 2.6 3.1 Cerambycidae Nocturnal/crepuscular Tree trunks 1.6 2.4 Unidentified adult Coleoptera ? ? 1.0 04 Unidentified larvae Coleoptera ? ? 1.0 0.4 Lepidoptera (unidentified small moth) ? ? 0.3 01 Lepidoptera (unidentified caterpillar) ? Foliage/branches 1.0 0 3 Formicidae (Atta sexdensqueen) Nocturnal/crepuscular, Ground 0.3 0.2 Diurnal Formicidae (Camp0n0tusspp.) Nocturnal/crepuscular, Tree trunks, 5.2 0.l Diurnal Ground Formicidae (Dorylinae) Nocturnal/crepuscular, Ground 1.9 0 1 Diurnal Formicidae (unidentified spp.) ? ? 3.2 0 1 Other unidentified Insecta ? ? 0.3 02 SUBTOTAL INVERTEBRATES -- -- 98.1 65 9 334 SHOP.T COMMUNICATIONS VOL. 36, NO. 4 and vertebratesin Venezuela, respectively.Prey taken by revised the Spanish text. This work was a small part of a these owls include katydids, beetles, cockroaches,small Ph.D. dissertationsponsored by Coordenaca6 De Aper- snakes, and rodents (Thomas 1977, Smith 1983, this feigoamento Ce PessoalDe Nivel Superior and World Wildlife Fund/Brazil. study). Larger species like Otus asio and O. kennicottii seem to include proportionallymore vertebratesin their LITERATURE CITED diets (e.g., Ritchison and Cavanagh1992, del Hoyo et al. BURTON,J.A. (ED.). 1992. Owls of the world: their evo- 1999). On the other hand, smaller speciessuch as O. lution, structure, and ecology, 3rd Ed. Peter Lowe, tr•6hopsis;O. fiammeolus, and O. cholibaappear to be mostly Wallingford, U.K. Insectivorous (Ross 1969, del Hoyo et al. 1999, this DEL HOYO,J., A. ELLIOTT,AND J. SARC,ATAI. ]999. Hand- study). book of the birds of the world. Barn Owls to hum- The frequent consumption of the terrestrial arthro- pods,Lutosa brasiliensis (Lycosidae) and others (68.5% by mingbirds.Vol. 5. Lynx Edicions,Barcelona, Spain. GAt,tAm)O,L.A. ANDJ.M.G, xt•t,^•r)o. 19B4. Observaciones number and 63.3% by biomass) suggeststhat prey are often captured on the ground (Table 1). A similar pat- realizadassobre el comportamientode Otuscholiba en liberdad. Comun. Mus. Argent. Cienc.Nat. Bernardino tern in the prey data supportsthat the Tropical Screech- Rivadavia Zool. 4:109-114. Owls were essentiallynocturnal; the diet consistsmainly J^•lC, F.M. ANDJ.H. C•OTHERS. 1985. Ecological,mor- of night prey (76.8% by number and 81.5% by biomass; Table 1 ). phological, and bioenergetic correlates of hunting mode in hawks and owls. Ornis Scand. 16:165-172. RESUMEN.--Se estudi6 la dieta del Autillo Ch61iba (Otus MEYERDF, SCHAUENSEE, R. 1966. The speciesof birds of South America and their distribution. Livingston,Nat- choliba)durante el periodo reproductivo,entre los meses berth, PA U.S.A. de octubre y diciembre de 1992 y 1993, en una localidad RITCHISON,G. AND P.M. CAVANAGtt.1992. Prey use by del Sudestede Brasil. Se identificaron pot lo menos 34 Eastern Screech-Owls: seasonal variation in central especiesde presasa parfir de egagr&pilas,directamente colectadas en tres nidos ubicados en cavidades de troncos Kentucky and a review of previous studies.J.