NOTES

A POTENTIAL THREAT TO BALD EAGLES IN BAJA CALIFORNIA SUR, MEXICO

GUSTAVO ARNAUD, EDGAR AMADOR, AND MARCOS ACEVEDO, Centro de InvestigacionesBio16gicas del Noroeste, S.C., Apdo. Postal 128, La Paz, Baja California Sur, M•xico 23000

The SouthernBald Eagle (Haliaeetus leucocephalus leucocephalus) is a resident speciesin the stateof BajaCalifornia Sur (Grinnell1928), occurringin mainlycoastal habitats.Nesting is now known only from Bahia Magdalena-Almejason the west coast(Henny et al. 1993, Amador-Silvaand Guzm•n-Poo1994, Rodriguez-Estrella et al. 1995) whereno morethan threepairs are foundannually. The physiographyof BajaCalifornia Sur is composedof extensiveplains and hills,the principalmountain rangesare the sierrasla Gigantaand la Laguna,and predominant vegetation is desert scrub,which covers92% of the statearea (INEGI 1995). Freshwaterhabitats are scarceand largelytemporary across the state. Duringbimonthly visits to the Sierrade la Gigantathat commenced in June1995 and continueto date,we haveobserved Bald Eagles on two occasions:On 13 April 1996 we observedtwo adults,and on 27 March 1997 a singleadult, soaring over a canyon locatedat 24 ø 50' N and 111ø 00'W (80 km westof BahiaMagdalena), at 250 meters abovesea level. This canyonincludes a seriesof permanentfresh-water ponds (locally knownas "pozas")ranging in sizefrom 35 to 100 m longand from 1 to 3 m deep. Unlikemost other oases in BajaCalifornia Sur, these ponds contain abundant fish of at leasttwo introducedspecies (Oreochromis urolepis homorum and Tilapia spp.). We have observedOspreys (Fandion haliaetus)fishing in theseponds on several occasionsand it seemslikely that Bald Eaglesmay alsoutilize this resource,at least occasionally.Local informantsreport that fishermanoccasionally shoot Ospreys, arguingthat these birds take the fishthey use for food.The huntingof Ospreyis illegal, suggestingthat fish-eatingBald Eaglescould also be targeted,a potentiallyserious threatto the relativelysmall and vulnerablepopulation nesting at Bahia Magdalena. Educationof the fishermenin this area regardingthe rarity of Bald Eaglesin Baja Californiacould be effectivein helpingto ensurethe futureof the peninsula'slast remainingnesting population of thisendangered raptor. We thankEduardo Palacios and LeopoldoMoreno for their criticalreview. Charles Henny and PeterBloom alsoreviewed and improvedthis note.

LITERATURE CITED Amador-Silva, E., and Guzmbn-Poo, J. 1994. El Aguila Calva (Haliaeetus leucocephalus)en IslaSanta Margarita, Baja California Sur, M•xico. Revistade InvestigacionesCientificas, Serie Cienciasdel Mar UABCS 5(1):33-35. Garcia, E. 1981. Modificacionesal sistemade clasificaci6nclimbtica de Koppen. UniversidadAut6noma de M•xico, Mexico City. Grinnell,J. 1928. A distributionalsummation of the ornithologyof LowerCalifornia. Univ. Calif. Publ. Zool. 32:1-300. Henny, C. J., Conant,B., andAnderson, D. W. 1993. Recentdistribution and status of BaldEagles in Baja California,Mexico. J. Raptor Res. 27:203-209. INEGI (InstitutoNacional de EstadisticaGeografia Informatica). 1995. Sintesis Geograficade Baja CaliforniaSur. Publicaciones INEGI, MexicoCity. Poole,A.E 1989. Ospreys.Cambridge Univ. Press,Cambridge, England. Rodriguez-Estrella,R., Donazar,J. A., and Hiraldo, F. 1995. Fishermenand their gearmay threaten Bald Eagles at MagdalenaBay, B.C.S., Mexico.J. RaptorRes. 29:144. Accepted 15 November 2000

136 Western Birds 32:136, 2001