314 SHORT COMMUNIGATIONS VOL. 32, NO. 4

LITERATURE CITED FULLER,M.R. •4DJ.A. MOSHER.1987. Raptor survey tech- niques. Pages37-65 in B.A. Giron Pendleton,B.A. CHEBEZ,J.C. 1994. Los que sevan. Especiesargentinas en Millsap, K.W. Gline and D.M. [EDS.], Raptor peligro. Editorial Albatros. management techniques manual. Natl. Wildl. Fed., COLL•, NJ, L.P. GONZ•G^,N. KR•BE, A. M^DROf40,L.G. Washington,DG U.S.A. N•UJO, T.A. P•qI•R )•ND D.C. WEGE. 1992. Threat- GI2a, A. 1952. Diccionario ilustrado de las aves argenti- ened of the Americas. The ICBP/IUCN red data nas. 1. Aves Gontinentales. Revista Mundo Agrario, book. SmithsonianInstitution Press,Washington, DC Editorial Haynes,Buenos Aires, Argentina. U.S.A. GIL, G., E. HAENEAND J.G. CHEBEZ.1995. Notas sobre la DE L• PEr4^,R.M. 1992. Las aves argentina. Editorial avifauna de Sierras de las Quijadas. NuestrasAves 31: L.O.L.A. 26-28. DE Lucc^, E.R. 1992. El/tguila coronada, Harpyhaliaetus S•'•LV2d)OR,S.A. AND P.G. EROLES. 1994. Notas sobre aves coronatus,en SanJuan. NuestrasAves 26:25. de Santiagodel Estero. NuestrasAves 30:24-25. 1993. Rapaces Amenazadas. E1 /tguila coronada. Nuestras Aves 29:14-17. Received30 January 1998; accepted 10 August 1998

J. RaptorRes. 32(4):314-318 ¸ 1998 The Raptor ResearchFoundation, Inc.

A COMPARISON OF METHODS TO EVALUATE THE DIET OF GOLDEN IN CORSICA

JEAN-FRANGOISSEGUIN ParcNaturel Rggional de Corse,B.P. 417, F-20184 Ajaccio,Corsica and EcolePratique des Hautes Etudes, Laboratoire de Biogdographieet Ecologie des Vertdbrds, Place Eugdne Bataillon, F-34095 MontpellierCedex 05, France

PATRICK BAYLE 15 rue Bravet, F-13005 Marseille, France

JEXN-CL•UDETHIBAULT AND Jos•. TORR• ParcNaturel Rggional de Corse,B.P. 41 7, F-20184Ajaccio, Corsica

JEAN-DEN•SVIGNE CNRS, URA 1415, MusdumNational d'HistoireNatureRe, Laboratoire d •tnatomieComparde, 55 rue Buffon,F-75005 Paris, France

KEYWORDS' GoldenEagle;, Aquila chrysaetos;diet;, Corsica. diet. Previousstudies of the diet of Golden Eagles(Aquila chrysaetos)in the Mediterranean area have been basedon Identification of prey remains, pellet analysisand di- the collection of prey remains, without taking into ac- rect observationof prey deliveriesare the principal meth- count any possiblebiases in the data collectedusing only this technique (Handrinos 1987, Cheylan 1983, Fasce ods used to study the diets of nesting raptors (Marti and Fasce 1984, Fernandez 1991, Grubac 1987, Huboux 1987). Although it is often best to observeor film nests 1984). Considering that the variety of food resourceson for long periods to quantify prey deliveries,this is not Mediterranean islands is limited (Seguin and Thibault alwayspossible due to time and logisticalconstraints. To 1996) with a moderate spectrum of potential prey, we assessthe validity of using prey remainsand pellets as a conducted this study to determine the best methods for means of determining diet, several authors have com- monitoring the diet of Golden Eagles on Corsica. pared data from collectionsof nest contentswith data obtained from direct observationfor variousraptor spe- STUDY AREA AND METHODS cies (Collopy 1983, Simmonset al. 1991, Mersmann et Corsica(42øN, 9øE) is one of the major islandsin the al 1992, Mafiosa 1994, Real 1996). Overall, they have westernMediterranean covering an area of 8750 km2. It found that by combining remains and pellets, collected supportsa breedingpopulation of 32-37 pairsof Golden with the same level of effort, it is possibleto determine Eagles (Torre 1995). Our study area, in the Verghello DECEMBER 1998 SHORT COMMUNICATIONS 315

Table 1. Minimal Number of Individuals (MNI), percentage of different prey according to different diet analysts methodsand correctionfactors (c.f.) for a Golden nest in VerghelloValley (Corsica),1992, 1994, and 1995

DELIVERED PREY REMAINS PELLETS REMAINS + PELLETS N= 79 N= 52 N= 50 N= 72

N % N % c.f. MNI % c.f. MNI % c.f.

Mammals Large mammals 31 39.2 30 57.7 + 1.47 25 50.0 + 1.28 32 44.4 + 1.13 Small mammals 6 7.6 1 1.9' -4.00 3 6.0 -1.27 4 5.6 -1.36

Birds Corvidae 10 12.7 11 21.2 +1.67 2 4.0* -3.37 ll 15.3 +1.20 Alectorisrufa 3 3.8 6 11.5' +3.03 2 4.0 +1.05 6 8.3* +2.18 Others 2 2.5 I 1.9 -1.32 3 6.0* +2.4 4 5.6* +2.24

Reptiles Coluberviridiflavus 27 34.2 3 5.8* -5.9 15 30.0 -1.14 15 20.8 -1.64 * Significantlydifferent from the frequenciesof delivered prey.

Valley, included one breeding pair that had been moni- Quantification of food remains was based on minimum tored by the Parc Naturel R•gional de Corsesince 1981. number of individualestimates (MNI) (Poplin 1976,V•g- We observedprey brought to this nest by adult eagles ne 1991) based on the number of the most frequent an- from mid-May to late July in 1992, 1994, and 1995. Dur- atomical part in food remains or the pairing of anatom- ing the three years, hatching occurred between 15-24 ical parts (e.g.,jaws). The drawbackof this method is that May and fledging occurred between 28 July-4 August.We it is impossibleto be totally objective in the pairing of made observationsusing a 20-60X spotting scope from bone pairs. Also, the most frequent speciesare underes- a blind located 200-250 m from the nest. Observers came timated in comparisonto rare (Poplin 1976). to and left from the blind at night in order not to disturb Prey were separated into six categories:large mammals the adults. Observations were made for 1 d every 2.5 d (Caprini, boar [Sus scrofa]and red fox [Vulpesvulpes]), with observationdays evenly distributed between hatch- small mammals (weasel [Mustela nivalis], European ing and fledging for a total of 1271 observationhr spread hedgehog [Erinaceuseuropaeus], and black rat [Rattusrat- over 82 d (1992--27 d, 1994•23 d, and 1995--32 d). tus]), birds (Corvidae, Red-leggedPartridge [Alectoris ru- Whenever possible,prey items were identified to species fal] and other birds), and snakes.Differences between and the identification was relatively easy because the taxa, years or prey categoriesobtained by both methods number of mammalian specieslikely to be taken by Gold- were tested with Chi-squarecontingency tables. en Eagles was low (15 taxa included eight domestic, Saint-Girons1989, Raveneau1993). However,not all prey RESULTS AND DISCUSSION could be identified due to poor visibility during obser- vation periods causedby heat, haze, and aggressivebe- Of the prey deliveredto the nest, 86% (N = 79, Table havior of the young as they took prey from adults. Do- 1) were whole. The remainder consistedof portions of mestic goat (Capra hircus)and sheep (Ovis aries) could large mammals (Caprini, boar and unidentified mam- not be differentiated in any cases,so they were grouped mals). Altogether, 39% of the prey delivered to the nest as Caprini. was large mammals, 8% was small mammals, 19% was In each of the three years,remains were carefullycol- birds including Red-leggedPartridges, Common Kestrels lected in and under the nest in late Augustafter fledging. (Falco tinnunculus),an unidentified raptor nestling, pt- Pellets were dissected and separated into bone frag- ments, feathers, reptile scales,and hair. Bonescollected geons (Columbaspp.), Common Raven (Corvus corax), in the nest or extracted from pellets were identified by and Eurasian Jay (Garrulus glandarius),and 34% was comparison with osteologicalcollections (Museum Na- snakes(western whip snake[ Coluberviridiflavus] ). No sig- tional d'Histoire Naturelie, Paris, France) following nificant difference appeared among the three years in methods of Payne (1985), Barone (1986), and Vigne the amount of these different prey that wasdelivered to (1995). Feathers (both from the nest or extracted from the nest (X2 = 3.23, df = 6, P = 0.78). Analysisof prey pellets) were identified by comparisonwith a reference remains collected at the nest showed the diet consisted collection. Hair was identified by comparisonwith Spill- of 44% large mammals,6% small mammals,29% birds, mann (1991). Becauseadults spent most of the time away from the nest after the youngwere 4-wk old, we assumed and 21% snakes.Again, no significant difference was that most pellets we collected from the nest were from found in the diet among the three years (X2 = 4.44, the young. Each speciesidentified in a pellet wascounted df-- 6, P = 0.67). as an individual. Bones contributed most data for the quantitative as- 316 SHORT COMMUNICATIONS VOL. 32, NO. 4

Table 2. Minimal Number of Individuals and number lets was 2.4 times greater than in prey deliveries. The of species(in parentheses) obtained from bone identifi- comparisonbetween prey delivered and remainsplus pel- cation and complementary data by pellet and feather ex- lets was not significant among the six prey categories amination from material collected in a Golden Eagle nest (X9 = 5.03, df = 5, P = 0.41). Nevertheless,the Red- in VerghettoValley (Corsica), 1992, 1994, and 1995. legged Partridge and other birds were two times more frequent than in the prey delivered.

BONES PELLETS FEATHERS Using all methods, 15 speciesof prey were identified (Table 3). Here also, there was no significantdifference Large mammals 30 (4) 3 (0) -- in the speciescomposition of the diet estimatedby direct Small mammals 1 (1) 3 (1) -- observationor by analysisof remains and pellets (X9 = Large birds 10 (2) 0 (0) 4 (1) 6.51, df -- 2, P = 0.99). Small birds 0 (0) 1 (1) 9 (3) One might expect that food habits data collectedonce Reptiles 3 (1) 12 (0) -- at the end of the nesting seasonwould be biasedin favor of large prey species.However, when adult Golden Eagles clean nests, females often eliminate the larger remains sessmentof MNI for large mammals and large birds (Ta- which could result in an underestimation of large prey ble 2). Pellets provided little additional information for species(Mathieu and Choisy 1982, Tjernberg 1981). This large mammals, but added additional data for estimating bias has been noted for other species(Real 1996). MNI for small mammals and snakes.Feathers provided Severalsources of bias exist in the resultsof prey anal- supplementary data on bird numbers, especially on ysisbased on remains only that are related to prey size smaller species.Analysis of bonesyielded the most infor- and factors affecting fragmentation of remains such as mation on the number of specieswhile pellet analysis removal when remains are taken out of nestsby females, better predicted occurrence of small mammals and birds difficulties in identification owing to wear, differencesin (Table 2). Feathersprovided the best estimatefor small the size of prey, and destruction of osteologicatremains. bird species. These factors probably explain the differences we ob- Comparisonof data obtained for prey delivered to the servedbetween the prey delivery and prey remainsmeth- nest with that of prey remains showed a significant dif- ods. One of the more important biaseswe found in the ference between the six categoriesof prey (X9 = 19.43, collection of prey remains of Golden Eagleswas the un- df = 5, P = 0.002). The number of mammalsand reptiles derestimationof the small prey items, in particular small •n the diet was underestimated, while birds are overesti- mammals and reptiles, because most of the time they mated in samplesof prey remains. In fact, the frequency were completelyeaten. This bias has been previouslyob- of small mammals was four times lower in remains than served in Golden Eagle dietary studies (Delibes et at. in prey delivered.Red-legged Partridge, in contrast,were 1975, Mathieu and Choisy1982, Tjernberg 1981), and of three times more frequent and western whip snakeswere other raptors (Simmons et at. 1991, Mersmann et at. s•x times lessfrequent. The small mammals, the Red-leg- 1992, Mafiosa 1994, Real 1996). Birds suchas Red-legged ged Partridge and the westernwhip snakecontributed to Partridges are overestimatedbecause of the abundance the significant difference between prey delivery and re- of sterna and feathers. Pellets overestimated birds other mains. The comparisonbetween prey delivered and pet- than corvids and Red-legged Partridges in the diet be- letswas not significantamong the six prey categories(X 9 cause they were eaten entirely. Assuming that the occur- = 4.51, df = 5, P = 0.48). Nevertheless, the Corvidae rence of a prey speciesin a pellet correspondsto an in- were three times lessfrequent in pellets than in prey de- dividual can also overestimate the number of large liveries.On the other hand, the frequencyof birds (ex- mammals in the diet since several pellets could contain cept the Corvidae and the Red-leggedPartridge) in pet- the remains of the same individual of a prey taxon eaten

Table 3. Overall number and percentageof speciesidentified by the different diet analysismethods (prey delivered, remains,pellets, and remains + pellets), at the Golden Eagle nest in VerghelloValley (Corsica), 1992, 1994, and 1995.

DELIVERED PREY REMAINS PELLETS REMA1NS + PELLETS

N % N % N % N %

Mammals (N = 6 species) 5 83.3 6 100.0 4 66.7 6 100.0 Birds (N = 8 species) 5 62.5 6 75.0 5 62.5 7 87.5 Reptiles (N-- I species) 1 100.00 I 100.0 1 100.0 I 100.0 Total (N = 15 species) 11 73.3 13 86.7 10 66.7 14 93.3 DECEMBER 1998 SHORT COMMUNICATIONS 317 over severaldays. No method givesa perfect estimateof the diet of Golden Eagles.J. Wildl. Manage.47:360- the nesting diet but combining remains and pellets 368. seems to be the least biased estimator of diet available if DELmES,M., J. CALr)ERONANt) F. HIRALr)O.1975. Selec- deliveriescannot be recorded. The complementaryna- cion de presa y alimentacionen Espafiadel Agmla ture between these two types of prey analysishas been real (Aquila chrysaetos).Ardeola 21:285-303. shownin previousstudies on raptor diet (Simmonset al. FASCE,P. AND L. FASCE.1984. L'Aquila reale in Italia. Lega 1991, Mersmann et al. 1992, Mafiosa 1994, Oro and Tella Iraliana ProtezioneUccelli, Parma, Italy. 1995, Real 1996). FEP,NANr)EZ, C. 1991. Variation clinale du rCgimealimen- The comparison of direct observationsand collection taire et de la reproductionchez l'Aigle royal (Aqmla of prey remains to determine the diet of Golden Eagles chrysaetos)sur le versantsud des PyrCnCes.Rev. Ecol. wasstudied by Collopy (1983), but in a region where the (Terre Vie) 46:363-371. largestprey was jackrabbits (Lepus californicus). Our study GRUBAC,R. 1987. L'Aigle royal en MacCdoine.Acres du wasthe first to comparethe different analyticalmethods premier colloque international sur l'Aigle royal en in an area where prey are larger than Leporidae. While Europe, Arvieux 1986. Maison de la Nature, Brian- either method gave similar resultsfor the percent fre- con, France. quency of prey in the diet of Golden Eagles, periodic HANDmNOS,G.I. 1987. L'Aigle royal en Grkce.Acres du observationsof food delivered to nestsare necessaryif premier colloque international sur l'Aigle royal en the main objectiveis estimateprey biomass(Collopy Europe, Arvieux 1986. Maison de la Nature, Brian- 1983), or to obtain information on selectionof prey ton, France. (Real 1996). Our data indicate that the combination of Hu•oux, R. 1984. Contribution •t une meilleure con- prey remainsplus pelletscollected on only one visitafter naissancedu rfigime alimentaire de l'Aigle royal en the breeding seasonwould enable the study of several pfiriode de reproduction pour les Alpes du Sud et la pairs of eaglesover a large area and a short period of time. Provence.Bull. Centrede RecherchesOrnithologiques de Provence 6:30-34. MAJ•os^, S. 1994. Goshawk diet in a Mediterranean area RESUMEN.--Numerososestudios sobre el rCgimenalimen- ticio del pollo de Aguila real (Aquilachrysaetos) est/m bas- of northeasternSpain. J. RaptorRes. 28:84-92. adosen el an/tlisisde losrestos 6seos o de lasegagrCpilas. MARTI,C.D. 1987. Raptor food habit studies.Pages 67- Pero, dado que dichosrestos sufren una degradaciCndi- 80 in B.A. Giron Pendleton,B.A. Millsap, K.W. Cline ferencial, los resultadospueden quedar sesgados.Desde and D.M. Bird [EDS.], Raptor management tech- esta optica hemos comparado durante cuatro periCdos niques manual. Natl. Wild. Fed. Washington, DC U.S.A. de reproducciCn, en una isle mediterr/mea, los restosde huesos,de egagrCpilasy de plumasencontrados en un MATHIEU,R. ANDJ.-P.CHOISY. 1982. L'Aigle royal dansles nido a los datosobtenidos por observaciCndirecta. Que- Alpes mCridionalesfrancaises de 1964/t 1980. Le B•g- da comprobadoque los diferentestipos de restosse com- vre 4:1-32. plementan,y que por consiguientesu recogiday an/tlisis MERSMANN,TJ., D.A. BUEHLER,J.D. FRASERAND J.K D con el mismo esfuerzo son necesariospare que la des- SEECAR.1992. Assessingbias in studiesof cripciCndel regimen alimenticiodel pollo de Aguila real food habits.J. Wildl. Manage.56:73-78. se acerque en 1o posible de la realidad. Oao, D. ANr)J.L.TELLPt. 1995. A comparisonof two meth- [TraducciCnde Pedro Arrizabalaga] odsfor studyingthe diet of the PeregrineFalcon. J RaptorRes. 29:207-210. ACKNOWLEDGMENTS PAYNE,S. 1985. Morphological distinctionsbetween the This study was financed by the Office de l'Enviro- mandibular teeth of young sheep, Ovis, and goats, nnement de la Corse and the DIREN, Minist•re charg6 Capra. J. Archcol.Sci. 12:139-147. de l'Environnement. Gary Bortolotti, Geoff Holroyd, POPLIN,F. 1976. A propos du nombre de resteset du Ron Jackman, and Mike Marquiss improved an earlier hombre d'individus dans les 6chantillons d'ossements. draft of the manuscriptwith their commentsand criti- cism. Cahierdu Centrede RecherchesPrghistoriques (Univ. Pans /) 5:61-74. LITERATURE CITED RAVENEAU,A. 1993. Inventairedes animaux domestiques BARONE,R. 1986. Anatomie comparCe des mammifkres en France. Nathan, Paris, France. domestiques. Tome 1. Ost6ologie. Vigot, Paris, REAL,J. 1996. Biasesin diet study methods in the Bo- France. nelli's Eagle.J. Wildl. Manage.60:632-638. CHEYLAN,G. 1983. Note sur l'alimentationde l'Aigle roy- SEGUIN,J.-F. ANDJ.-C. THIBAULT.1996. Ajustement de al Aquila chrysaetosen BasseProvence. Bull. Centrede l'alimentation de l'Aigle royal (Aquila chrysaetos)•t la RecherchesOrnithologiques deProvence 5:56-57. disponibilit6saisonnikre des proies pendant la pCri- COLLOPY,M.W. 1983. A comparison of direct observa- ode de reproduction en Corse. Rev.Ecol. (Terre Vze) tions and collectionsof prey remains in determining 51:329-339. 318 SHORTCOMMUNICATIONS VOL. 32, NO. 4

SAINT-GIRONS, M.-C. 1989. Les mammif•res en France. TORRE,J. 1995. L'Aigle royal (Aquilachrysaetos) en Corse: Sang de la Terre et La Manufacture, Paris, France. r•partition et biologie de la reproduction. Trav. Sc. SIMMONS, R.E., D.M. AVERY •ND G. AVERY. 1991. Biaises ParcNat. Rdg.Res. Nat. Corse51:87-90. in diets determined from pellets and remains:correc- V•GNE,J.-D. 1991. The meat and offal weight (MOW) tion factorsfor a mammal and bird-eatingraptor. J. method and the relativeproportion of ovicaprinesin RaptorRes. 25:63-67. some ancient meat diets of the north-western Medi- SPILLMANN,P.-L. 1991. Atlasdes pois desmammif•res sau- terranean. Rivistadi StudiLigruri 57:21-47. rages terrestres de Corse. M•m. Maitrise Sci. Tech., 1995. Crit•res de d•termination des onglons Universit• de Corse, Corta, Corsica. d'artiodactylesde Corse pour une contribution /t la connaissancedu r•gime alimentairedu Gypa•te. Rev. TJERNBERG,M. 1981.Diet of the Golden EagleAquila chry- Ecol. (Terre Vie) 50:85-92. saetosduring the breeding seasonin Sweden.Holarct. Ecol. 4:12-19. Received12 October 1997;accepted 27July 1998

j. RaptorRes. 32(4):318-321 ¸ 1998 The Raptor ResearchFoundation, Inc.

A Rl•colm OF A HARPY EAGLE FROM EASTERN PARAGUAY

THOMAS M. BROOKS •

Departmentof Ecology and Evolutionary Biology, 569 DabneyHall, Universityof Tennessee, Knoxville, TN 3 7996-1610 U.S.A.

I•Y WORDS: HarpyEagle; Harpia harpyja;Paraguay; sight on the back, scapularsand wing coverts,with black lower record. on the wings.I did not seethe upperwingsor uppertail in flight. On 2 August1995, I recordedan immatureHarpy Ea- Not all of the salientcharacters, notably the enormous gle (Harpia harpyja)in rainforest at ReservaPrivada Itab6 tarsiand the dividedcrest could be seendue to the angle (24ø20'S,54ø35'W), Departamento Canindeyfi, Paraguay. of observation.However, nothing about the bird indicat- The Harpy Eagle is poorly known in Paraguayand has ed that it wasa CrestedEagle (Morphnusguianensis). Im- not been previouslyrecorded at this site. mature CrestedEagles are distinguishedfrom immature I first sightedthe perched eagle in an emergent tree Harpy Eaglesby their slimmerbodies, long tails,smaller beside the main road through the reserve.It had been bills, dark lores,black-tipped crests and long, relatively forced into the tree by a flock of sevenWhite-eyed Par- small tarsi. Light phase CrestedEagles also have white akeets(Aratinga leucopthalmus). After 10 min, the bird was underwingcoverts contrasting with barredremiges (Hilty againmobbed by the parakeetflock, causing it to fly off and Brown 1986). CrestedEagles have not been record- into the adjacentforest canopy. ed in Paraguay(Hayes 1995), althoughthey havebeen There wasno questionthat the bird wasa HarpyEagle. historicallyrecorded in Misiones Province,Argentina Its mostobvious feature was its large,completely creamy- (Naroskyand Yzurieta 1987). white facial disc.Its bill was dark grey and its eyeslarge I excluded other large raptorssuch as Mantied Hawk and black. Several completely white feathers formed a (Leucopternispolionota), Black-and--Eagle (Spi- crest on its head. Its breast and belly were a uniform zasturmelanoleucus) , Black Hawk-Eagle ( LSpizaetustyrannus) creamywhite exceptfor a pale grey area acrossits breast. and Ornate Hawk-Eagle (S. ornatus)based on the size The undertailappeared dark brownand the underwings and bulk of the bird alone and the plumage of the bird appearedpale with somedark barring. I hardly sawthe I observeddid not match the plumagesof any of these upperpartsbut they appearedto be largelygrey, at least species(Narosky and Yzurieta1987). The latter three spe- cies are known from Reserva Privada Itab6 (Lowen et al. 1Present address: Department of BiologicalSciences and 1996). Center for Advanced Spatial Technologies, 12 Ozark The Harpy Eagle is rare throughout its range from Hall, Universityof Arkansas,Fayetteville, AR 72701U.S.A. Mexico to Argentina. It wasconsidered Globally Threat-