92 SHORT COMMUNICATIONS VOL. 39, NO. 1 y los polluelos salieron de los nidos entre noviembrey DELHOYO, J., A. ELLIOTT,AND J. SARGATAL(EDS.). 1994 diciembre. Los nidos fueron de construcci6nendeble y Handbook of the birds of the world. Vol. 2. New constituidospor ramas secasy se situaron en las bifur- World Vultures to Guineafowl. Lynx Edicions, Barce- cacionesde las ramas de firboles a una altura promedio lona, Spain. de 15 m sobre el suelo (N = 3). Las dimensionespro- FERGUSON-LEE,J. AND D.A. CHRISTIE.2001. Raptors of the medio de los nidos fueron 39.5 X 39.5 cm y 13.9 cm de world. Houghton Mifflin Company, Boston, MA profundidadexterior, con una copa de 21.5 x 22.5 cm y U.S.A. 7 8 cm de profundidad.E1 tamafio modal de la nidada FERRARI,S.F. 1990. A foraging associationbetween two fue dos (N = 3 nidos). Los huevospresentaron manchas kite species(Ictinia plumbeaand Leptodoncayanensis) de color car6 con marcas mils ruerres en la base (N = 6 and buffy-headed marmosets (Callithrixfiaviceps) in huevos)y tuvieronun tamafio promedio de 51.5 x 40.8 southeastern Brazil. Condor 92:781-783. mm (N = 4). Los polluelos eclosionaronde forma asin- FOSTER,n.s. 1971. Plumage and behavior of a juvenile cr6nica. En total, de tres intentos de nidificaci6n, dos Gray-headedKite. Auk 88:163-166. polluelos emplumaron exitosamente,lo que representa HAVERSCHMIDT,F. 1962. Notes on the feeding habitsand un 6xito de nidificaci6ndel 66.6%. Todaslas presas11e- food of some hawks in Surinam. Condor 64:154-158. vadasa los polluelosen el nido fueron serpientes(N = LINS, L.V. AND M.P. MENDONCA. 2000. Lista Vetmelba das 9). esptcies ameagadasde extin•io da flora de Minas [Traducci6n del equipo editorial] Gerais. Publica•6es avulsasda Funda•5o Biodiversitas e Fundagio Zoo-Bot•mica de Belo Horizonte, Belo ACKNOWLEDGMENTS Horizonte, Brazil. We thank Russell Thorstrom for an earlier review of SICK,H. 1997. OrnitologiaBrasileira. Editora Nova Fron- this manuscript, Robson Silva e Silva for supplyingref- teira, Rio de Janeiro, Brazil. erence material and literature, Jane Elce Scheid Ramos THORSTROM,R.K. 1997. A descriptionof nestsand be- for help in the preparation of the manuscript,INMET-- havior of the Gray-headedKite. WilsonBull. 109:173- National MeteorologyInstitute (5ø MeteorologyDistrict) 177. for providing us with climatic data on the first studied area, and Dave Whiracre for his information, references, , D.K WHITACRE,J. LOPEZ,AND g. LOPEZ.In press and review. Gray-headedKite (Leptodoncayanensis). In D. Whitacre [ED.], Raptorsof the Maya Forest:ecology of a trop- LYI ERATURE CITED ical forest raptor community.Cornell Univ. Press,Ith- BROWN,L. ANDD. AMADON.1989. Eagles,hawks, and fal- aca, NY U.S.A. consof the world. The Wellfleet Press,Seacaucus, NJ U.S.A. Received 15 July 2003; accepted19 September 2004

j RaptorRes.39(1):92-94 ¸ 2005 The Raptor Research Foundation, Inc.

COOPERATIVENESTING BY A TRIO OF BOOTED EAGLES(HIERAAETUSPENNATUS)

Jose E. MARTINEZ,1 CARLOS GONZALEZ, AND JOSl• F. CALVO Departamentode Ecologfae Hidrologia,Universidad de Murcia, Campusde Espinardo, 30100 Murcia, Spain

KEYWORDS: BootedEagle,, Hieraaetus pennatus; coopera- that this wasa frequent phenomenonin well-studiedspe- twe breeding,,polygamy; polygyny; trio. cies and that the mating systemwas probably not deter- mined in many other speciesbecause of the difficulty in Although monogamyis the most common mating sys- making appropriate observationsand given the fact that tem among raptors, alternative systemslike polygyny, many raptors have not been well studied (Kimball et al. polyandry,and cooperativebreeding have been recorded 2003). Cooperativebreeding has been observedamong in severalspecies (Newton 1979, Korpimilki1988, Stacey 3% of bird species,including at least42 diurnal raptors and Koening 1990). A recent reviewon the topic showed (Brown 1987, Kimball et al. 2003). Here, we report a caseof cooperativenesting by a trio in an intensively-monitoredbreeding population (21-29 1 Email address:[email protected] pairs) of Booted Eagles (Hieraaetuspennams) in south- MARCH 2005 SHORT COMMUNICATIONS 93

easternSpain. Our observationswere made in 2001 in a tree most of the time. The helper female (F2) was ob- mountainousarea of the Region of Murcia (southeastern served only twice with F1 in the nest. When the male Spain), characterizedby large tractsof pine forests(Pinus approached the nest with prey, it emitted food-begging halepensis)interspersed with smaller clearingsof cultivat- calls,which prompted calling from both females.F2 was ed lands and scrubland. The Booted Eagle is a medium- never observeddelivering prey to nest. On one occasmn sized,territorial raptor that nestson treesand rockycliffs both females attacked a Common Raven (Corvus corax). •n forested areas of the Palearctic and sub-Saharan re- The pair and the helper female successfullyreared one gions (del Hoyo et al. 1994). This speciesis considered young,who flew for the first time between5-10July 2001 a monogamousraptor (Newton 1979, Cramp and Sim- mons 1980) and to our knowledgeno instancesof trios DISCUSSION at nests have been reported. The above describedcase of apparent polygynycan be In the Iberian Peninsula, Booted Eaglesare generally considered cooperative breeding because all the mem- summer residents,arriving from their wintering grounds bers of the breeding unit contributed to the care of a in late March and early April. In our study area, nest single nest (Kimball et al. 2005). We suggestthat coop- building or reconstructionoccurs soon after the eagles erative breeding in the Booted Eagle is uncommon be- arrive and their mean laying date is 24 April. cause of the lack of reports in the scientific literature.

OBSERVATIONS Nevertheless, we must be cautious with this affirmanon due to the difficulty in observingthis kind of behawor, In 2001, during the pre-laying period, a polygynous especiallyfor a specieswith poorly known breeding bi- trio wasobserved in one territory on the studyarea. The ology, as is the caseof the Booted Eagle (Veiga and Vifi- sameterritory wasmonitored in the previousyear related uela 1994, Su•rez et al. 2000). to other research.This studyin 2000 involved 195 hr of The presence of helpers at raptor nests has been as- nest observationsthat allowed us to photograph and in- sociatedwith many factors,including productivehabitats dividually identify the pair composedof a pale-morph with abundant food supply (Van Kleef and Bustamante male (M1) and a dark-morphfemale (F1). This female 1999), low prey densities (Doyle 1996), biased sex ratio wastrapped and marked with a radiotransmittermount- in adults (Oring 1986, Arroyo and Garza 1986), the re- ed with a backpack harness.She laid two eggsand the duced availabilityof suitable sitesfor reproduction (He- pair reared two young successfully. redia and Donfizar 1990, Bertran and Margalida 2002), In 2001, when the trio was recorded, we observed the saturation of breeding territories (Heredia and Donfizar nest for 46 hr. The male who occupied this nest wasthe 1990), potential benefitsof group living (Garcelon et al. same male observed the previous year (M1) based on 1995, Kimball et al. 2005) and benefits to yearlings that distinctivefeatures of its plumage (blond head and neck, gain breeding experience (Zuberogoitiaet al. 2005). The and white breast with numerous brown streaks).The pre- Booted Eagle is a philopatric species(Cramp and S•m- vious year's female (F1) was identified becauseof the mons 1980), thus a possibleexplanation is that the help- transmitter. The third bird in the territory was a pale er was an individual born in the study area some years morph individual identified as an adult (the adult plum- ago and returned to its natal area for the first time. ageis acquiredat the third calendaryear; Forsman 1999) Whether the helper was recruited by the adults to assist female (F2) due to its size and behavior.No copulations with the breeding effort or was a previous offspring of were observed between M1 and either female. Also, dur- the pair was unknown. Based on our limited observa- ing the pre-layingperiod, no aggressiveinteractions be- tions, it was unclear which factors may have led to th•s tween the three indMduals were observed. Instead, all cooperativebreeding event. We encourageother observ- three eagles added material to refurbish the nest, al- ers working on Booted Eagles to make an effort to rec- though the bulk of this taskwas done by M1 (20%) and ognize individual breeders and that researchersshould F1 (70%; N = 10 deliveries of nest material). be awareof the possibilityof cooperativebreeding in this When the nest was checked on 29 April it was defend- species. ed by the adults (M1 and F1), and contained two eggs. Both females were observed to incubate the eggs, al- REPRODUCCION COOPERATIVA POR UN TRiO EN HIERAAETUS

though F1 spent more time (93%; N = 540 min) than PENNATUS the accompanyingfemale (7%). We also observedthe relief of F1 by F2 from the incubationon three occasions, RESUMEN.--En esta comunicaci6n se describe un caso de which occurred when the former left the nest to partic- reproducci6n cooperativapor un trio poliginico de H•- ipate in territorial defense,to hunt, or apparentlyto take eraaetuspennatus en una zona forestal del surestede Es- a rest. In contrast, while F1 incubated, F2 perched on a pafia. El trio, observadoen 2001, estabacompuesto por nearby tree. Although F2 brought greenery to the nest, un macho de rase clara, una hembra consorte de rase it wasonly F1 who situatedthe greeneryin the nest. oscura,y una hembra acompafiantede rase clara. No se During the nestling period, the two hatched young observaron c6pulas. Ambas hembras colaboraron en las were only fed by F1, while F2 stoodperched on a nearby tareas de mantenimiento, incubaci6n y defensadel nido 94 SHOP,T COMMUNICATIONS VOL. 39, No. 1

Sin embargo,la hembra consortecontribuy6 mucho mas polyandrous trios in an endangered population of en las actividadesreproductivas que la hembra acompafi- Lammergeiers Gypaetusbarbatus in northern Spain. ante; 6stafiltima no fue nunca observadatrayendo presas Biol. Conserr. 53:163-171. al nido o cebando a los pollos con el alimento aportado KIMBALL,R.T., P.G. PAm4ER,AND J.C. BEDNA•Z.2003. The por el macho. occurrence and evolution of cooperative breeding [Traducci6n de los autores] among the diurnal raptors (Accipitridae and Falcon- idae). Auh 120:717-729. ACKNOWLEDGMENTS KORPI 'MAKI,E. 1988. Factors promoting polygynyin Eu- We are indebted to Gin•s Gtmez and Martina Carrete ropean birds of prey--a hypothesis.Oecolo•a 77:278- for field assistance.We also thank Beatriz Arroyo, Javier 285. Balbontin, Jim Bednarz, and one anonymous referee for NEWTON,I. 1979. Populationecology of raptors.T. & A.D. helpful comments on the manuscript. Poyser,London, U.K. LITERATURE CITED ORINC,L.W. 1986. Avian polyandry.Pages 309-351 in R.F Johnston [ED.], Current ornithology.Plenum Press, ARROYO, B. AND g. (}ARZA. 1986. Estudio sobre la situacitn New York, NY U.S.A. del •tguila real Aquila chrysiietosen el sistemacentral. STACEY,P.B. ANDW.D. KOENING(EDs.). 1990. Cooperative Bol. Est. Cent. Ecol. 30:93-104. breeding in birds: long-term studies of ecology and BERTP•N,J. ^ND A. M_•G^I.ID^. 2002. Social organization behavior. Cambridge University Press, Cambridge, of a trio of Bearded Vultures (Cupaetusbarbatus): sex- U.K. ual and parental roles.• RaptorRes. 36:66-69. SUJmEZ,S., J. BALBONTiN,AND M. FERPmR.2000. Nesting BROWN,J.L. 1987. Helping and communal breeding in habitat selection by Booted EaglesHieraaetus pennatus birds. Princeton Univ. Press,Princeton, NJ U.S.A. and implicationsfor management.) Appl.Ecol. 37 CP,AMP, S. ^ND K.E.L. SIMMONS. 1980. The birds of the 215-223. western Palearctic. Vol. 2. Oxford Univ. Press, Oxford, VAN KLEEF,H. ANDJ. BUSTAM•NTE.1999. First recorded U.K. polygynousmating in the Red KIte (Milvusmilvus). J DELHo¾o, J., A. Et.TJOTT,AND J. SA•C^T^t_1994. Hand- RaptorRes'. 33:254-257. book of the birds of the world. Vol. 2. Lynx Edicions, VEIG^,J.P. ANDJ. Vff½UET•.1994. Booted Eagle Hieraaetus Barcelona, Spain. pennatus.Pages 182-183 in G.M. Tucker and M.F. DOY•.E,F.I. 1996. Bigamy in Red-tailed Hawks in south- Heath [EDS.], Birds in Europe: their conservationsta- westernYukon. J. RaptorRes. 30:38-40. tus. BirdLife International, Cambridge,U.K. FORSMAN,D. 1999. The raptorsof Europe and the Middle ZUBEROGOITIA,I., J.A. MARTINEZ,A. AZKONA,A. IP,•T^, I. East:a handbook of field identification.T. & A.D. Poy- CASTILLO,R. ALONSO,AND S. HIDAI.GO. 2003. Two cas- ser, London, U.K. GARCEI.ON, D.K., G.L. SLATER, C.R. DANILSON, AND R.C. es of cooperative breeding in Eurasian Hobbies. J HELM. 1995. Cooperativenesting by a trio of Bald Ea- RaptorRes. 37:342-344. gles.• RaptorRes'. 29:210-213. HEREDIA,R. ANDJ.A. DONAZA•.1990. High frequency of Received6 October 2003; accepted27 July 2004

j. RaptorRes. 39(1):94-97 ¸ 2005 The Raptor Research Foundation, Inc.

TIMIN(; AND ABUNDANCE OF MIGRANT RAPTORS ON BONAIRE, NETHERLANDS ANTILLES

VINCENTNIJMAN, • TINEKE G. PRINS,AND .J.H. (HANS)REUXE• Institutefor Biodiversityand EcosystemDynamics, Zoological Museum, University of Amsterdam,P.O. Box94766, 1090 GT Amsterdam, Netherlands

KEY WORDS:American Kestrel; Falco sparverius; Swallow- The island of Bonaire (12ø10'N, 68ø18'W) in the south tinled Kite; Elanoides forficatus; Yellow-headedCaracara; Caribbean Sea, 87 km north of Venezuela, is the eastern- Mfivago chimachima; mi•ation, Caribbean. mostisland of the NetherlandsAntilles. Bonaire occupies a land surface of ca. 272 km •, its climate is arid, and the island is largely coveredin xerophyticand thorny bush 1 Email address:[email protected] and sparse woodland. Some 181 speciesof birds have