Peregrine Falcon Recovery Along the West Central Coast of the Baja California Peninsula, Mexico

THE JOURNAL OF RAPTOR RESEARCH A QUARTERLY PUBLICATION OF THE RAPTOR RESEARCH FOUNDATION, INC.

VOL. 31 MARCH 1997 NO. 1 j. RaptorRes. 31(1):1-6 ¸ 1997 The Raptor ResearchFoundation, Inc.

PEREGRINE FALCON RECOVERY ALONG THE WEST CENTRAL COAST OF THE BAJA CALIFORNIA PENINSULA, MEXICO

ARADIT CASTELLANOS Centrode InvestigacionesBiologicas del Noroeste, S.C., Div. De Biol. Terrestre.,Apdo. Post. 128, La Paz, B.C.S., Mexico

FERNANDOJARAMILLO PG7 Consultores,S.C., Apdo. Post. 1887, Cuernavaca,Mor., Mdxico

FEDERICO SALINAS, ALFREDO ORTEGA-RUBIO AND CERAFINA ARGUELLES Centrode Investigaciones Bioldgicas del Noroeste, S.C., Div. deBid. Terrestre.,Apdo. Post. 128, La Paz, B.C.S., Mgxico

ABSTRACT.--Thecentral west coastof the Baja California peninsula was an important Peregrine Falcon (Falcoperegrinus) breeding area supportinga population of about 13 breeding pairs. This population declined drasticallyduring the 1960sand early 1970s.We conductedfield surveysand compiled data on nestingPeregrine pairs from 1980-94 to addressthe current statusof the Baja population. We found 10 pairs nestingin the area indicating the Peregrine population has recoveredin the area sincethe late 1970s.Due to increasedhuman activityin the area, proper management is needed to provide suitable nestingsites and to minimize human disturbancesduring the nesting season. KEYWOWDS: PeregrineFalcon; recovery; status; Baja California;Falco peregrinus.

Recuperaci6ndel halc6n peregrinoen la costacentro occidentalde la penisulade Baja California,Mfxico. RESUMEN.--Lacosta centro occidentalde la peninsula de Baja California, ha sido un /trea importante de reproducci6ndel halc6nperegrino (Falco peregrinus), manteniendo alrededor de 13 territoriosde anidaci6n. Estapoblaci0n declin6 drfisticamente entre losaftos 1960s e iniciosde los1970s. Nosotros realizamos estudios en el campoy recabamosdatos sobre las parejas anidantes de peregrinosentre 1980y 1994 para determinar su situaci6nactual. Encontramos diez parejasde peregrinosanidando en el/trea. Nuestroshallazgos sugieren que los peregrinosse han estadorecuperando desde finales de los aftos1970s. Las actividadeshumanas est•n creciendoen el/trea, lo que representatanto amenazascomo oportunidadespara los peregTinos.Se requiere de un manejo apropiadoque proveeade sitiosadecuados de anidamientopara minimizarlas p6rdidasreproductivas asociadas al hombre durantela estaci6nreproductiva. [Traducci6n Autores]

Peregrine Falcon (Falco pereg,inus) recovery now returned to pre-DDT levels (Kiff 1988, New- has been documented in several regions of the ton 1979, Ratcliffe 1993). The ban on DDT use world (Fyfe 1988, Kiff 1988, Ratcliffe 1993, En- in many countries (Ratcliffe 1993) and the suc- derson et al. 1995). Nesting territories, deserted cessof Peregrine recovery programs (Fyfe 1988, during the decline of the speciesare now being Ratcliffe 1993) has contributed to the Peregrine's reoccupied by breeding pairs. Reproduction has removal from endangered statusand to a redesign 2 CASTELLANOSET AL. VOL. 31, NO. 1

28'00'

•North

Csstro

Pdicsnos Is.

+ 26•30' 1-3 19•0 • Breedingpairs

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Figure1. Recentrecords of nestingPeregrine Falcons on the central west coast of Baja California, Mexico. (Shaded areas are Banks, 1969 records.)

of its managementstrategies (Walton and Thelan- servation needs on the west central coast of the der 1988). Baja California peninsula. The historical and current status of the Mexican STUDY AREA AND METHODS Peregrine Falcon population is not well known (Banks1969, Fyfe et al. 1976). Populationsin the The studyarea, a part of E1Vizcaino biosphere reserve, coversabout 350 km along the westcoast of Baja Cali- Baja Californiapeninsula and the Gulf of Califor- fornia, Mexico (Fig. 1). The studyarea includes:desert nia are known to have declined between 1967-84 islands,a coastalfringe of mostlysandy beaches and two (Porter et al. 1988). By 1976, the Baja west coast big coastallagoons with extensivewetlands (Massey and population,once containing 38 breedingpairs, was Palacios 1994). Most of the area is covered with halo- phyticvegetation, 30 cm high.Mountains are restricted consideredon the brink of extirpation (Fyfe et al. to Benitos and Cedros Islandsand some parts of the El 1976). However,recent reportsof newlyoccupied Vizcafno reserve. nestingterritories in thisarea (Danemanand Guz- We used three data sourceson the breeding popula- mfin Poo 1992, Castellanos et al. 1994) suggest a tion of PeregrineFalcons in the area. Data from 1980- 85 were obtainedby F.Jaramillo during wildlife invento- recoveryis in process.In this report,we provide ries to promotethe creationof the E1Vizcaino Reserve information on current numbers, distribution, and and in 1994 on Cedros and Benitos Islands. Data from productivityof Peregrines,and discusstheir con- Ojo de Liebreand SanIgnacio lagoons were obtained by MARCH1997 PEREGRINERECOVERY IN BAJACALIFORNL4 3

A. Castellanos,F. Salinas,C. Argueliesand A. Ortega in lings were produced per nest (Table 2). This pro- 1993-94. Nesting surveysof breeding PeregrineFalcons ductivityappeared to be within the range of pro- were conducted by searchingthe plateaus,canyons, hills and islands on foot and inspecting all potential nesting ductivityfor healthy populations(Cade et al. 1988, sites using binoculars. Boats were used to explore the Ratcliffe 1993). lagoons and to reach the islands.We also used recent The Peregrine Falcon is defined by Mexican law recordsin the oologicalcollection of the WesternFoun- as a vulnerable species(Diario Oficial 16 de Mayo dation of Vertebrate Zoology (WFVZ) and personal re- portsfrom other individualobservers. We comparedour de 1994). In spite of its status,lack of national re- data with those of Banks (1969). Productivityof breeding covery programson threatened specieshas failed pairswas estimated by checkingthree nestsin 1993 and to produce management plans in their Mexican five nests in 1994. range. The use of organochlorine pesticidesin the region is not well documented but it has appar- RESULTS AND DISCUSSION ently been reduced since the late 1970s.Studies We located at least 10 nestingpairs of Peregrine conducted then and in the late 1980s in Baja Cal- Falcons in six locations in the surveyarea, includ- ifornia, the Gulf of California and in northwestern ing smallislands in the open sea,islets inside coast- Mexican waterfowl wintering areas show pesticide al lagoonsand an inland mountainouszone (Fig. levelsin eggsand bird tissuesare among the lowest 1). The maximum number of pairs seenin a single in North America (Spitzer et al. 1977, Mora et al. year was six pairs in 1994 when we observedpairs 1987). This evidence leads us to believe that cur- on San Roque islands,Laguna Ojo de Liebre (Pie- rent organochlorinepesticide use does not repre- dras Island and E1 Chaparrito navigationchannel) sent a major threat for Peregrinesin the region. and San Ignacio Lagoon (Pelicanoand Ballena Is- We did, however,identify other threats to breed- lands) (Fig. 1, Table 1). Becausenot all the histor- ing Peregrines in the area. Nests on the ground ical and potential nesting siteswere surveyed,we are accessibleto dogs and catsabandoned by fish- considered this to be a minimum estimate of the ermen in the islands. Coyotes (Canis latrans) tem- total number of breeding pairs in the area. The porarily invade Piedrasisland in Ojo de Liebre La- historical population estimate for the study area goon destroying the nests of Peregrines, Ospreys was about 13 pairs (Banks 1969). and other birds. We found coyote tracks at one Breeding pairs were found on small cliffs, di- failed Peregrine nest in 1994 and presumed the rectly on the ground, in Ospreynests and on arti- coyote caused the nest failure. Avian depredation ficial structuressuch as channel markers and ship- by Western Gulls (Larus occidentalis)and Common wrecks. Ojo de Liebre (Scammon's) lagoon nest Ravens (C0rvus corax)is also a problem. Gulls and sites were new (Castellanos et al. 1994). Lack of ravens apparently caused the disappearance of inland nesting recordsfrom the studyarea led us three eggs from a nest on a tower over the water to believe that the cliff-nestingpairs on Pacific in Ojo de Liebre lagoon. North Vizcaino (near Sierra San Josfi de Castro) A third and more serious threat to nesting Per- were also new to the breeding population. A nest- egrines in the area is from humans when fishing, ing record in the WFVZ reported by B. Reitherman tourism and other human activities cause inciden- in 1981 documenteda pair nestingat San Ignacio tal disturbances at nests (Daneman and Guzman Lagoon for the first time. Daneman and Guzmfin Poo 1992). The studyarea is still relativelyinacces- Pot (1992) also found two pairs nesting there in sible and partially uninhabited, thus, habitat de- 1989. struction apparently is not yet a factor of concern. In addition to the 10 nesting pairs, there were The coastallagoons, islands and wetlandswithin several recent single sightings and two probable the study area support a magnificent avifauna nest site reports from Benitos and Cedros islands which provides adequate numbers and variety of (Fig. 1, Table 1). Nearestnesting site distances var- Peregrine prey (Masseyand Palacios 1993). New ied between 4.4 and 60 kin. Nests were 4.4 km ertheless, the density of breeding Peregrine Fal- apart in San Ignacio lagoon and 8 and 22 km apart cons in the area seems to be rather low for such in Ojo de Liebre lagoon (Fig. 1) an ideal location. Most of the resident pairs re- We followed the reproductive successof three ported are coastal or "small island Peregrines" pairs during 1993 and five pairs during 1994, lo- (Ratcliffe 1993) nesting on small cliffs or even on cated at Ojo de Liebre and San Ignacio Lagoons. the ground. This is apparently because of a short- An averageof 3 eggs,1.8 nestlings,and 1.6 fledg- age of suitable natural nesting sites on the main- 4 CASTELLANOSET AL. VOL. 31, NO. 1

Table 1. Historical and recent recordsof nesting Peregrine Falconsin the central west coastof Baja California. Recent records are from 1980-94.

LOCALITY SOURCESAND DATE INDIVIDUAL/NEST REFERENCE

San Benitos Islands Walker, 1927 and 1950 4 nests Banks (1969) Tyler, 8 April 1930 Nest with 2 eggs WFVZ, this study Harrison, 1 April 1938 Nest with 2 eggs WFVZ, this study 22 March 1992 1 seen This study Cedros Island Kaeding, 1905 Common, breeding Banks (1969) Carpenter,2 April 1932 Nest with 4 eggs WFVZ, this study 8, 31 July and 18 August 1980 1 seen This study April 1991 1 seen This study 2, 3 and 15 March 1992 1 pair, 2 sightings This study 22 March 1992 1 female, 1 male This study

Natividad Island Sechrist, 12 March 1917 Nest with 4 eggs WFVZ, this study Lamb, December 1924 6 pairs resident Banks (1969) D.S.D., 6 April 1930 Nest with 3 eggs WFVZ, this study Bancroft, 3 April 1932 2 nest with eggs WFVZ, this study 31 July 1985 1 breeding pair This study Ojo de Liebre Lagoon 26 January 1982 1 seen This study June, October, November 1984 1 seen This study 29 .July1985 2 females and 2 males This study 21 September1985 1 seen This study 1993 (Castellanos et al. 1994) 3 breeding pair This study San Roque Island Huey, 20 April 1927 Nest with 2 eggs Banks (1969) D.S.D., 5 April 1930 Nest with 3 eggs WFVZ Harrison, 6 April 1932 Nest with 4 eggs WFVZ, this study L. Flores, 1994 1 breeding pair L. Flores pers. comm. Asuncion Island Walker, 1938 1 pair Banks (1969) San Ignacio Lagoon Reitherman, 11 April 1981 Nest, 2 young, 2 eggs WFVZ, this study September1985 1 pair, one seen This study Daneman & Guzmfin Poo, 1992 2 breeding pairs Daneman & Guzmfin Poo, 1992 March-June, 1994 2 breeding pair This study Pacific North Vizcaino 13 June, 1984 1 breeding pair This study .June 1984 1 breeding pair This study 4 November 1984 2 seen This study March and September 1985 2 seen This study MA•CH 1997 PEREGRINERECOVERY IN BAJACALIFOP, NIA 5

Table 2. Peregrine Falcon reproductive successduring Hickey [Ed.], Peregrine Falcon populations. Univ. 1993-1994 on the Scammon'sand San Ignacio lagoons. Wisconsin Press, Madison, WI U.S.A. CADE,T., J. ENDERSON,C. THELANDERAND C.M. WroTE. 1993 1994 1988. The role of organochlorine pesticidesin Pere- grine population changes.Pages 463-468 in T. Cade, SEAM- SCAM- SAN J. Enderson, C. Thelander and C. White [Eds.], Per- MON'S MON'S IGNACIO egrine Falcon populations:their management and re- LAGOON LAGOON LAGOON covery.The Peregrine Fund, Boise, ID U.S.A. CASTELLANOS,A., F. SALINAS-ZAVALAAND A. ORTEGA-RU- Occupied nestschecked 3 3 2 Productive nests 3 1 1 mo. 1994. Statusand reproduction of the Peregrine Falcon at a coastallagoon in Baja California Sur, Mex- Total eggslaid 10 10 4 ico. J. RaptorRes.28:110-112. Eggsfailed to hatch 1 -- -- DANEMAN,G.D. ANDJ. GUZMANPOO. 1992. Notes on the Eggsdisappeared -- 6a -- Eggsbroken -- I b I b birds of San Ignacio Lagoon, Baja California Sur, Mexico. Western Birds 23:11-19. Average clutch size 3.3 3.3 2.0 DIARIO OFICIAL DE LA FEDERACI(SN. 1994. Tomo Nestlings 9 3 3 CDLXXXIX, No. 10, 16 de Mayo de 1994. Secretaria Nestling disappeared 1 1 de Gobernaci6n. Total young fledged 8 2 3 ENDEPSON,J.H., W. HEINRICH,m. KIFF AND C.M. WHITE. Nestlings/occupiednest 3 1.0 1.5 1995. Populationschanges in North American Pere- Fledglings/occupiednest 2.6 0.6 1.5 grines. Pages142-161 in Trans. 60th North American Fledglings/productivenest 2.6 2.0 3.0 wildlife and natural resources conference. Wildlife Probablyavian and coyotedepredation. Management Institute, Washington, DC U.S.A. Unknown causes. FYFE,R.W. 1988. The Canadian Peregrine Falcon recovery program 1967-1985. Pages599-610 in T. Cade,J. land coast, inland and on small islands, a factor Enderson, C. Thelander and C. White [Eds.], Pere- that limits cliff-nestingraptors in other areas (Rat- grine Falcon populations:their management and re- cliffe 1993). Peregrinesdo take advantageof suit- covery.The Peregrine Fund, Boise ID U.S.A. FYFE,R.W., S.A. TEMPLEAND TJ. CADE.1976. The 1975 able artificial nestingsites when theywere available North American Peregrine Falcon survey. Can. F•eld in the study area (Castellanoset al. 1994) Nat. 90:228-273. Giventhese circumstances, we suggestthe imple- K•FF,L.F. 1988. Changes in the statusof the Peregrine mentation of a Peregrine ConservationProgram in in North America: an overview. Pages 123-139 in T the E1Vizcaino Reserve,focusing on the following: Cade,J. Enderson,C. Thelander and C. White [Eds.], a) regular surveysof historicaland new nestingter- Peregrine Falcon populations:their managementand ritories to assessthe current population statusand recovery.The Peregrine Fund, Boise, ID U.S.A. trends; b) studies of biology and nesting ecology MASSEY,B.W. AND E. PALACIOS. 1994. Avifauna of the wet- to enhance knowledge of this poorly known resi- lands of Baja California Mexico: current status.Stu&es dent population; c) installationof artificial nesting in Avian Biology15:45-57. MORA, M.A., D.W. ANDEPSONAND M.E. MOUNT. 1987. substratesto increase the population on the main- Seasonalvariation of body condition and organochlo- land coast and at coastal lagoons; and d) an edu- rines in wild ducks from California and Mexico J. cation program to promote public awarenessof Wildl. Manage.51 (1):132-141. this and other speciesof wild birds. NEWTON,I. 1979. Population ecologyof raptors.Buteo ACKNOWLEDGMENTS Books, Vermillion, SD U.S.A. We thank L. Kiff for permitting us to use the Western PORTER,R.D., M.A. JENmNS,M.N. KIRVEN,D.W. ANDEPSON Foundation of Vertebrate Zoology oological collection, ANDJ.O. KEITH. 1988. Status and reproductive per- M. Acevedo for his field assistance and L. Flores for un- formanceof marinePeregrines in BajaQalifornia and publisheddata on Peregrines.The researchwas support- the Gulf of California, Mexico. Pages 105-114 in T. ed by the CIBNOR, S.C., CONACYT (Project 3031N), Ex- Cade,J. Enderson,C. Thelander and C. White lEds.I, portadorade Sal, S.A. and the SEMARNAP.Thanks to W. Peregrinefalcon populations:their managementand Wehtje, M.F. Campana for his academicsupport and R. recovery.The Peregrine Fund, Boise,ID U.S.A. Bowersand Dr. Ellis Glazier for editing of this English language paper. RATCLIFFE,D. 1993. The Peregrine Falcon. Academic Press,San Diego, CA U.S.A. LITERATURE CITED SPITZER,P.R., R.W. RISEBROUGH,J.W. GRIERAND C.R. SIN- BANI•S,R.C. 1969. The Peregrine Falcon in Baja Califor- DEIA•,JR. 1977. Eggshellthickness-pollutant relation- nia and the Gulf of California. Pages 81-91 in JJ. ships among North American Ospreys.Pages 13-19 6 CASTELLANOSET AL. VOL. 31, NO. 1

in J.C. Ogden [Ed.] Trans. North American Osprey derson, C. Thelander and C. White [Eds.], Peregrine research conference. U.S. Nat. Park Serv. Proc. Ser. 2, Falconpopulations: their managementand recovery. Washington,DC U.S.A. The Peregrine Fund, Boise,ID U.S.A. WALTON,BJ. ANDC.G. THELANDER.1988. PeregrineFal- con managementefforts in California,Oregon, Wash- ington and Nevada.Pages 587-597 in T. Cade,J. En- Received28 February 1996; accepted28 November1996