The Golden Eagle (Aquila chrysaetos) has been little studied in Mexico so that this species' population status in the .... shepherd, the eagle was accompanied by a second. Golden Eagle. ... Life histories of North American birds of prey. (Part 1.) ...
J. Raptor Res. 25(3):68-71 ¸ 1991 The Raptor ResearchFoundation,Inc.
NEW GOLDEN EAGLE RECORDS FROM BAJA CALIFORNIA RICARDORODRiGUEZ-ESTRELLA, JORGELLINAS-GUTI•RREZAND JORGECANCINO Centrode Investigaciones Biolggicas, Apdo.Postal728, La Paz, 23000, B.C.&, Mexico
ABSTRACT.--TheGolden Eagle (Aquilachrysaetos) has beenlittle studiedin Mexico sothat this species' populationstatusin the southernextremeof its range is unknown.We presentnew recordsof the species for the mid and southernportion of Baja California. We describethe recoveryof an eaglebandedin Oregonand founddeadin the Vizcaino Desert,approximately2000 km southof the bandinglocation. Basedon sightingsand recoveriesof dead eagles,we suspectthat a residentbreedingpopulationexists in the regionand that this populationis augmentedby migrantsin winter.
Nuevos registros de,kguilaRealenBajaCalifornia EXTe,_•CTO.--E1 ,kguilaReal(Aquila chrysaetos) ha sidomuypocoestudiada enM6xico,y pr/tcticamente se desconoce la situaci6nde suspoblaciones en el extremomils al sur de su distribuci6nen Am6rica. Nosotrospresentamos nuevosregistrosde la especieen la porci6nmediay sur de la peninsulade Baja California,M6xico,asl comoel registrode un figuilaanilladaen Oreg6ny que fue encontrada muerta en la zona del Desiertode Vizcaino,aproximadamente a 2000 km de su lugar de origen.Finalmentese
discutesobreel estatusdel Aguila Real en Baja Californiaen relaci6na los individuos residentes e invernantes.
The Golden Eagle (Aquila chrysaetos) in North Americais widely distributed,rangingfrom north-
izedby low precipitation(up to 100 mm annually) with a winter rainy seasonand a meanannualtem-
ern
perature of 22øC. High mountainsreceive200-300 mm of annual precipitationwith a summerand winter rainy seasonand havea meanannualtemperature of 20øC(Garcia and Mocifio 1968). Vegetation of the area is deserticthicket,comprisedmainly of mesquite(Prosopisspp.), Adam's Tree (Fouquieria diguetti), Palo Verde (Cercidium microphyllum), Cardons(Pachycereuspringlei) andseveralothercacti species(Le6n de la Luz et al. in press).Potential prey for eaglesare Black-tailedJackrabbits(Lepus californicus), the endemicgroundsquirrel (Spermophilusatricapillus),California Quail (Callipeplacalifornica)and PronghornAntelope(Antilocapra americanapeninsularis).All of thesespeciesare locally common,exceptthe pronghorn,which is endangered in the Vizcaino desert (Wilcox 1988). During April, July and October1984,November 1987, February-March 1988 and October1989, 13 Golden Eagles (10 adults, 1 subadult,and 2 immatures;seeClark and Wheeler 1987 for a description of age classes)were observedat different sites
Canada
and Alaska
to north-central
Mexico
(Bent 1937, Brown and Amadon 1968); however, there
is little
information
on the distribution
and
statusof this eaglein Mexico (Le Franc and Clark 1983). Nothing appearsto be publishedaboutbreeding and migrant Golden Eaglesin Baja California, particularlysouthof SierraSanPedroMfirtir (Grinnell 1928). There are no museumspecimens in Mexico or the United Statesfrom Baja California (P. Unitt, and P. Escalante,pers. comm.). We report on observations of Golden Eaglesin the Peninsula of Baja California, and contributenew information on the distribution of these eaglesat the southern end of their range. Our observations consisted mainly of individuals from the mountainsof the Vizcaino BiosphereReserve,althoughsomeindividualsalsowere recorded farther south,on the tip of the Peninsula.We particularlysurveyedthe higher(SanFranciscoand La Higuera) and the lower (San Jose de Castro and Santa Clara) sierras,includingthe isolatedmountains of E1 Pinacateand Cerro Prieto (Fig. 1). El- (Table 1). All wereflyingovermountains andvalleys evationsin the surveyedarea range from 550-600 surroundedby hills. We did not observeevidenceof m in the lower mountains to 1400-1600 m in the reproductiveactivity, but in 1988, two probable higher mountains.Lower mountainsare character- GoldenEaglenests,oneon the Sierra SanFrancisco 68
FALL1991
GOLDENEAGLES IN BAJACALIFORNIA
69
N
-28 ¸•
50 km SIERRA
SAN FRANCISCO
SIERRA DE MARTHA
SIERRA SAN
SIERRA
JOS• DE CASTRO -27
% SAN PEDRO
C. EL PINACATE O C. PRIETO
CAtiON PURJSIMA*
SIERRA SANTA CLARA SN. IGNACIO*
LORETO*
-26 O
,SIERRA LA GIGANTA
--250 SIERRA LAS TARABILLAS ISLA
.•CERRALVO* -24 ¸
* ISLA
SIERRA
STA. MARGARITA
BOCA DEL
ALAMO SIERRA LA TRINIDAD
SIERRA LAS CRUCES
SIERRA
LA LAGUNA
-23 ¸
115¸ I
114 ¸ I
113o I
112 o I
111¸ I
110¸ I
Figure1. Golden Eaglerecords inBajaCalifornia Sur.Points show thelocations whereGolden Eagles wereobserved. Asterisks (*) indicate recordsfrom the literature.
70
RODRiGUEZ-ESTRELLAET AL.
VOL. 25, NO. 3
Table 1. Golden Eagle recordsin Baja California. Recordsfor this studywere collectedsince1984 in the southern end of the range of the Golden Eagle. NUMBER SITE
North
of Vizcalno
DATE
OF
INDIVIDUALS
SOURCE
Desert
Nachoguero(32029') Ensenada (31043') Laguna Hanson (31039')
5 October1946 9 April 1967
I 1,a la
Hill and Wiggins 1948 Short 1967
21 October 1926
lb
Grinnell 1928
Santo Tomils (31ø31') San Telmo (30049')
7, 8 October 1946 16 October 1946 -- 1893 21 October 1946
1, 2 Several 2c 3
Hill and Wiggins 1948 Hill and Wiggins 1948 Anthony1893 (citedin Grinnell 1928) Hill and Wiggins 1948
San Jos6(30048')
October1946
Nestd
Hill andWiggins1948
20 October 1946 25 February 1925 15 June 1923 -- 1895 26 October 1946 17 April 1977
I I I I I I
Hill and Wiggins 1948 Huey 1926 Huey 1926 Anthony1893 (citedin Grinnell 1928) Hill and Wiggins 1948 Wilbur 1987
1, 1, 1, 2, 2
This study
1, I 2a 1 1 2 I 1, 2, 2; 2
This study This study This study This study This study Wilbur 1987 This study
17 November1946 15 January 1985 25 April 1984
I I 1
Hill and Wiggins 1948 Wilbur 1987 Amador 1985
26 October
1
Banks
I 1 1,a 1
This study(seetext) This study (seetext) This study
San Quintln (30031') La Grulla (30o04') San Fernando (29059' ) E1 Mfirmol (29048') Isla San Lorenzo (28ø31') Vizcaino
Desert
Cerro E1 Pinacate (27032')
7, 9, 10-12 July 1984
Sierra San Francisco (27'31') Sierra Santa Martha (27025') Sierra de la Cabra (27024') Sierra de Santa Clara (27008')
San Ignacio(27002') San Hip61ito(26059')
11, 12 March 1988 27 October 1989 19 March 1988 17 November1987 14 October 1984 17 January 1985 13, 14, 17 April; 15 Oct. 1984
South
of Vizcaino
Desert
Cafi6n Purlsima (26020') Loreto (25053') Isla Santa Margarita (24024') Isla Cerralvo (24ø12') Los Planes (24o05') La Rivera (23ø31') Sierra de la Laguna (23ø19')
1961
June 1988 November 1989 25 January 1990
1963
a Immature.
bSkeleton in the Museumof VertebrateZoology,Universityof California,Berkeley. c Eaglesnesting.
dA nestin goodrepairin a Pinusponderosa.
and oneon the Sierrade la Higuera, were foundon cliffs with an ENE exposure.They were both unoccupiedat the time. Someof the eaglesobservedin our studyarea may be from U.S.A. While interviewing ranchers,we found a banded foot of a Golden Eagle that had been killed by a shepherdin November 1986 at Sierra San Francisco(2 km eastfrom Rancho Santa
Ana at 950 m elevation).This eaglewas 10 years old when killed, was of unknown sex, and it was near fledging when banded in Oregon. Conserva-
tively, this bird moveda minimum of 2000 km to arrive in the Sierra San Francisco.Accordingto the shepherd,the eaglewas accompanied by a second Golden Eagle. SomeGolden Eagleshave beenrecordedsporad-
FALL1991
GOLDENEAGLES IN BAJACALIFORNIA
71
helpfulcomments that improvedpreviousdrafts.For help with the Englishrevisionof this manuscriptwe thank F. Fauchetand D. Aurioles. Financial supportwas provided bur 1987). Our data suggestthat Golden Eagles by Secretarlade DesarrolloUrbano y Ecologla,Centro occurin the southernportionof the Baja peninsula de Investigaciones Bio16gicas de B.C.S. and Secretarlade morecommonlythan previouslybelieved.One in- Programaci6ny Presupuesto.
icallyfarthersouthalongtheBajapeninsula (Hill andWiggins1948,Banks1963,Amador1985,Wil-
juredadulteaglewastrappedby a rancheronJune 1988near Los Planesvillage(site:E1 M•dano Alto 24001'30"N 109ø55'15"W), and a sub-adult eagle
wastrappedaliveby a rancheron November1989, near La Rivera village(23ø33'36"N109ø30'40"W) (Fig. 1) whenthe individualtriedto chasea duck and had descended to the ground.On January 1990, we observedone immature (2-3 yearsold) and one
adult in the pine-oakforestof Sierrade la Laguna (1800 m elevation;Fig. 1). The statusand distributionof Golden Eagles in
LITERATURE
CITED
AMADOR, E.S. 1985. Avifauna de la Isla Santa Mar-
garita,B.C.S., MOxico.Memoria presentadapara optar al titulodeBi01ogo Marino. UniversidadAut6noma de Baja CaliforniaSur. La Paz, B.C.S., MOxico. BANKS,R.C. ifornia.
1963. Birds of Cerralvo Island, Baja Cal-
Condor 65:500-512.
BENT,A.C. 1937. Life historiesof North Americanbirds of prey. (Part 1.) U.S. National Museum, Bull. 167. BROWN,L. ANDD. AMADON. 1968. Eagles,hawksand falconsof the world. Country Life Books,London, U.K.
BajaCaliforniahasnotbeenclearlydetermined. For CLARK,W.S. AND B.K. WHEELER. 1987. A field guide example,there couldbe two GoldenEagle poputo hawks of North America. Houghton Mifflin Co., lationsin theVizcainoBiosphere Reserve,onelocal Boston, MA. andnonmigratory, andanothermigratory.Non-mi- GARCIA,E. AND P. MocIflO. 1968. Los Climas de la gratoryresidentsmight breedin the area, but curBaja California.Memoria 1966-1967 del Comit6Narentlythereare no publishedrecordsof this eagle cional Mexicano para el DeceniDHidrolOgicoInternacional. Instituto de Geoflsica, Universidad Nacional nestingsouthof latitude 30*N in Baja California Auton6ma de MOxico, Mexico City, Mexico. (Grinnell 1928, Short 1967, Wilbur 1987). However,basedon our discovery of two probableGolden GRINNELL,J. 1928. A distributionalsummationof the ornithologyof Lower California.Univ.Calif.Publ.Zool. Eaglenests,the presence of two immaturesin Sierra 32:1-500. San Francisco,and the presenceof oneimmaturein HILL, H.M. ANDL. WIGGINS. 1948. Ornithologicalnotes Sierradela Lagunawe suggest it maybeoccurring. from Lower California. Condor 50:155-161. Alternatively, thepresence ofonemigranteaglefrom HUEY, H. 1926. Birds of northwesternBaja California.
the U.S.A. in the Reservearea, aswell asthe increase
in GoldenEagle abundanceduringthe winter (accordingto the shepherd'sinformationand the literature;Table 1), suggests thisareamay well be an importantwinteringareafor the GoldenEaglesmigratingto Baja California. Clearly,moreinformationis neededto document the relationshipbetweenGoldenEagle populations of the U.S.A. and Mexico, particularlywith respect to dispersal andmigratorymovements. We alsoneed to determinemoreaccuratelythe breedingrangeof this species in the peninsulaof Baja California. ACKNOWLEDGMENTS
We thank F. Hiraldo, M. Delibes, J. Bustamante,B. Sanabria,J.L. Le6n de la Luz, and R. Cadenafor their field assistance. 1'. Unitt identifiedthe Sierra de la Laguna
•mmaturerecord.M. Collopy,M.N. Kochert,M.R. Fuller, S.R. Wilbur, J.R. Murphy, and B.A. Millsap made
Auk 45:552-555.
LE FRANC, M.N.
AND W.S. CLARK. 1983. Working
bibliography of theGoldenEagleandthegenusAquila. National Wildlife Federation,Washington, D.C. LEONDE LA LUZ, J.L., J. CANCINOANDL. ARRIAGA.In Press. Asociaciones fisonOmico-florlsticas y flora.Pages 85-119 in L. ArriagaandA. Ortega[EDs.],La Reserva de la Biosfera"El Vizcaino." Centro de Investigaciones
BiolOgicas deBajaCaliforniaSur,La Paz, M•xico. SHORT,L.L., JR. 1967. Noteson the avifaunaof northwesternBaja California. Trans.San Diego$oc.Nat. Hist.
14:281-500.
WILBUR,S.R. 1987. Birds of Baja California. University of California Press.Berkeley,CA. WILCOX, B. 1988. 1988 Red List of Threatened Animals. International
Union
for Conservation
of Nature
and Natural Resources.Cambridge, U.K.
Received29 October1990; accepted9 March 1991
