SHORT COMMUNICATIONS j Raptor Res. 27(3):161-163 ¸ 1993 The Raptor Research Foundation, Inc.

NOTES ON THE DIET OF THE APLOMADO FALCON (F.qLcoFL'MORA•.•S) IN NORTHCENTRALCHILE

JAIME E. JIM•NEZ1 Departmentof Wildlifeand Range Sciences,118 Newins-ZieglerHall, Universityof Florida, Gainesville,FL 32611 U.S.A.

The AplomadoFalcon (Falcofemoralis) is distributed Aplomado Falcons are uncommonat Auc6; however, from the southwestern United States south throughout they can be seen at least once a month all year round, South America to Tierra del Fuego (Cade 1982). Aplo- either aloneor in pairs, mostlyusing fiatlands and rolling mado Falcons inhabit open savannasand desert grass- hills. During 1991, two pairs nestedclose to the Reserve (B. Pefia pers. comm.). lands, from coastalplains at sea level to elevationsup to Between26 January and 8 February 1992, I collected 4000 m in the Andes (Johnson1965, Hector 1985). In prey remainsand pelletsunder perchesand pluckingsites Chile the Aplomado Falcon was considereduncommon used by Aplomado Falcons. The data collection period throughoutits range (Goodall et al. 1951), but more re- wasafter the breedingseason (Jim•nez pers.obs., Johnson cently,Jaksi• and Jim•nez (1986) reevaluatedits status 1965). as frequent in northern Chile, rare and increasingin the I identifiedthe collectedmaterial by comparingit with center of the country, and scarcein the south. voucherspecimens from the Chilean Museum of Natural Despitethe AplomadoFalcon's wide distributionin the History. I usedHector's (1985: 337) methodto determine Americas,its biologyis still little known. Most accounts the number of individualstaken. Prey weights were de- of the speciesdeal with anecdotaldescriptions of its feeding rived from Jim•nez and Jaksi• (1989a, 1989b) supple- mented with personalfield records.I assumedall insects habits (see Hector 1981 and referencestherein). An ex- weighed 1 g; a conservativeestimate for the large insects ceptionis the detailed study of the diet and hunting be- typically captured. Geometric mean prey weights were havior of F. f. septentrionalisin northern Mexico (Hector calculated(Hector 1986, Jim•nez and Jaksi• 1989a). 1985, 1986) whose quantitative analysisof the falcon's d•et revealedits mainly ornithofagousfeeding habits, sup- RESULTS AND DISCUSSION plementedwith large insects. I found three pellets and abundant feathers, represent- Here, I describe the diet of Aplomado Falcons in a ing 40 individual prey items. Becauseof the small sample locality of northcentralChile, the first suchinvestigation size conclusions should be drawn with caution. in SouthAmerica. I then comparethe findingswith those Aplomado Falcons at Auc6 hunted primarily birds of Hector (1985, 1986) in Mexico. (55.5%of totalprey by number),followed by insects(42.5%; Table 1). Only one reptile, a lizard, was identified from STUDY AREA AND METHODS prey remains. When consideringprey weight, the rank The study area encompassedthe 4570 ha Chinchilla order of the prey taken by the falconsdid not change,but National Reserve(31ø31'S 71ø06'W) at Auc6 and its sur- the relative importanceof birds in the diet increaseddra- roundings.The reserve lies closeto the town of Illapel, matically from 55.5-96.7%. Insectsmade up an insignif- 300 km north of Santiagoin northcentral Chile. The cli- icant amountof the prey biomass(1.7%). mate is semi-aridand the topographyof the site is rugged In general,my resultsare consistentwith previousqual- with deepgorges and steepslopes (> 15ø) interspersed with itative (Housse 1945, Johnson 1965) and quantitative fiatlandsand broad,open ravines with gentleslopes (< 15ø). (Hector 1985, 1986) reportson the diet of AplomadoFal- The latter habitattypes made up 23.2%of the Auc6surface cons.In contrastto Cade (1982), Chilean AplomadoFal- (correctedby slope).The semi-desertvegetation is domi- consdid not hunt small mammals, although two diurnal nated by thorny deciduousshrubs with sparsecacti and rodentspecies (Akodon olivaceus and Octodondegus) occur bromeliadson the morerocky north-facing slopes. Grasses, at the site and are taken by eight other local raptors and herbs, small shrubs, and bare soil dominate the flatter by two foxes(Jaksi• et al. 1992). Thus, this falcon is the areas (seeJim•nez et al. 1992). only vertebratepredator at Auc6 which apparently does not hunt mammals. At Auc0, AplomadoFalcons captured at least 11 bird • Presentaddress: Department of Biology,Utah StateUni- speciesbelonging to four orders and sevenfamilies (Table versity, Logan, UT 84322 U.S.A. 1). The frequencyof the birds capturedwas relatively

161 162 SHORTCOMMUNICATIONS VOL. 27, NO. 3

Table 1. Prey takenby AplomadoFalcons in Auc6,northcentral Chile. Numbersin parenthesesare for prey classes. The bird nomenclaturefollows Araya and Millie (1989). The geometricmean weight for birds and for total prey were computed(mean _ SD).

NUMBER % OF DIET PREY WEIGHT OF INDI- (g)a VIDUALS NUMBER BIOMASS Birds (34.29 +__1.77) (22) (55.5) (96.7) Black-wingedGround-Dove, Metriopelia melanoptera 125b 1 2.5 13.4 Band-wingedNightjar, Caprimulguslongirostris 45c 1 2.5 4.8 Giant Hummingbird, Patagonagigas 16c 1 2.5 1.7 White-throatedTapaculo, Scelorchilus albicollis 60d 1 2.5 6.4 Fire-eyedDiucon, Pyrope pyrope 38d 1 2.5 4.1 Chilean Mockingbird,Mimus thenca 66d 2 5.0 14.2 Long-tailedMeadowlark, Sturnella loyca 113d 1 2.5 12.1 MourningSierra-finch, Phrygilus fruticeti, male 32d 1 2.5 3.4 female 26 c 4 10.0 11.1 Band-tailedSierra-finch, Phrygilus alaudinus 18d 2 5.0 3.9 Diuca-finch, Diuca diuca 25c 4 10.0 10.7 Rufous-collaredSparrow, Zonotrichia capensis 19d 1 2.5 2.1 Passeriformes, unidentified 41 e 2 5.0 8.8 Reptiles (1) (2.5) (1.6) Rough-scaledlizard, Liolaemusnitidus 15d 1 2.5 1.6 Insects (17) (42.5) (1.7) Scarabaeidae, unidentified 1 1 2.S 0.1 Bostrichidae, unidentified 1 1 2.S 0.1 Tenebrionidae, unidentified 1 3 7.S 0.3 Carabidae, unidentified 1 2 5.0 0.2 Chagual moth, Castniapsittacus 1 5 12.5 O.5 Sphecidae,unidentified 1 1 2.5 0.1 Cicadidae, unidentified 1 3 7.5 0.3 Gryllidae, unidentified 1 1 2.5 0.1 Total prey (7.48 _+6.08) (40) (100) (100) a Weightsources: b = afterJim&nez and Jaksi6 (1989b); c = Jim&nez(unpubl.); d = afterJim•nez and Jaksi• (1989a); e = weight estimatedas the geometricmean weight of knownarian prey. Insectswere assumedto weigh 1 g.

evenly distributedamong species,although only 30% of The importanceof insectsin the diet of AplomadoFal- the 37 potentialavian prey speciesin Auc6 were hunted cons is underestimated when biomass is considered. How- by AplomadoFalcons (Jim&nez and Jaksi• 1989a). It is ever, the 1 g weight assumptionfor insectprey may be surprising that no tinamu (Nothoproctaperdicaria) was too low; insectstaken were quite large, especiallythe cha- captured becausethe speciesis very abundant at the site gualmoths (Castnia psittacus). As reportedby Hector(1985) (pers. obs.),and has beendescribed elsewhere as the pre- for Mexican AplomadoFalcons, the mostcommon insect ferred prey of AplomadoFalcons (Housse 1945, Johnson prey for the Chilean birds were mothsand cicadas. 1965). In northcentralChile, AplomadoFalcons take few- The geometricmean weight of prey taken at Auc6 is er insectivorousbirds (one speciesout of 10) and relatively much smallerthan that for Mexican AplomadoFalcons more seed-eatingspecies. Conversely, in Mexico, most (Hector1981; 7.48 vs.23.8 g, respectively;Table 1). How- prey of AplomadoFalcons are insectivorousbirds (Hector ever, the figure for bird prey is remarkably closeto the 1985). The fact that Chilean Aplomadostake fewer in- one found for male Mexican AplomadoFalcons (Hector sectivorousbirds, as well as fewer insects,may have im- 1986): 34.29 vs. 34.98 g, respectively. portant conservation-relatedimplications. Aplomado Fal- Althoughthe samplesize is small, this studyshows that cons in Chile may be relatively less affected by the AplomadoFalcons rely mostlyon avian prey, apparently organochlorinepesticides still in use than are Mexican paying no attentionto potential mammalianprey. Insects falcons (Kiff et al. 1980). made a minute amount of these falcons' diet. The results SEPTEMBER 1993 SHORT COMMUNICATIONS of this study agreewell with another quantitativestudy 2. Platt EstablecimientosGrificos S.A., Buenos Aires, conductedin the northern end of the Aplomado Falcon Argentina. distribution. HECTOR,D.P. 1981. The habitat, diet, and foraging behavior of the Aplomado Falcon, Falco femorahs RESUMEN.--Abase de restosde presasy contenidosde (Temminck). M.S. thesis,Oklahoma State Univ., Still- egagr6pilasse estudia la dietadel halc6nperdiguero (Falco water, OK U.S.A. femoralis)en la localidadde Auc6 (31ø31'S71ø06'W), en Chile centronorte. Tanto en nilmero como en biomasa, las 1985. The diet of the AplomadoFalcon (Falco presasmss abundantesson las aves (55,5 y 96,7%, res- femoralis) in eastern Mexico. Condor 87:336-342. pectivamente).Los insectoss61o son importantes desde el 1986. Cooperativehunting and its relationship puntode vistanumbrico (42,5%), pero su contribuci6nen to foraging successand prey in an avian predator. biomasaen casi nula (1,7%). La presenciade reptiles en Ethology73:247-257. la dieta es escasay los mamlferosno sonconsumidos por HOUSSE,R. 1945. Las aves de Chile en su clasificaci6n estos halcones. Comparados con halcones perdigueros moderna,su vida y costumbres.Ediciones de la Univ. mexicanos,los estudiadosen Chile tienen una dieta muy de Chile, Santiago, Chile. similar en los tipos y tamafiosde las presasconsumidas. JAKSI•, F.M. AND J.E. JIMP,NEZ. 1986. The conserva- Sin embargo, los perdigueroschilenos consumen menos avesinsectlvoras y mils granlvorasque los mexicanos. tion statusof raptors in Chile. Birds Prey Bull. 3:95- 104.

ACKNOWLEDGMENTS , --, S.A. CASTROAND P. FEINSINGER. 1992 The commentsof John Smallwood,Carl Marti, Alan Numerical and functionalresponse of predatorsto a Jenkins,and two anonymousreviewers greatly improved long-termdecline in mammalian prey at a semi-arid the manuscriptquality. Permissionfor workingand lodg- Neotropical site. Oecologia89:90-101. ing at the sitewere providedby CONAF (Chile's Forest JIM•NEZ, J.E. ANDF.M. JAXSI•. 1989a. Biologyof the Service).I expressmy gratitudeto Juan Carlos Torres- austral pygmy-owl. WilsonBull. 101:377-389. Mura, bird curator of the Chilean Museum of Natural -- AND--. 1989b. Behavioralecology of grey History,who kindly allowedaccess to the vouchercollec- eagle-buzzards,Geranoaetus melanoleucus, in central uon. This work was partially fundedby the Lincoln Park Chile. Condor 91:913-921. Zoo ScottNeotropic Fund, the Tropical Conservationand DevelopmentProgram of the Universityof Florida, and --, P. FEINSINGERAND F.M. JAKSId. 1992. Spa- grantFONDECYT 92/0038 from Chile'sNational Fund tiotemporal patterns of an irruption and decline of for Scientificand TechnologicalDevelopment. I wrote this small mammals in northcentral Chile. J. Mammal. 73. article while I held a Fulbright fellowship. 356-364. JOHNSON,A.W. 1965. The birds of Chile and adjacent regionsof Argentina, Bolivia and Peril. Vol. I. Platt LITERATURE CITED EstablecimientosGrificos S.A., BuenosAires, Argen- ARAYA,B. ANDG. MILLIE. 1989. Gula de campode las tina. aves de Chile. Editorial Universitaria. Third edition, KIFF, L.F., D.B. PEAKALL AND D.P. HECTOR. 1980. Santiago,Chile. Eggshellthinning and organochlorineresidues in the CADE,T.J. 1982. The falconsof the world. Cornell Bat and AplomadoFalcons in Mexico. Proc. 17th In- Univ. Press, Ithaca, NY U.S.A. ternat. Ornithol. Congr., Berlin, Germany. GOODALL,J.D., A.W. JOHNSONAND R.A. PHILIPPI. 1951. Las avesde Chile, su conocimientoy costumbres.Vol. Received15 February 1993; accepted7 April 1993