BREEDING BIRDS OF THE GUERRERO NEGRO SALTWORKS, BAJA CP-!-!FORNIA SUR, MEXICO

GUSTAVO D. DANEMANN, Afegua,Asociaci6n para el Estudioy la Conservaci6n de las Aves de la Peninsulade Baja California, A. C., Apartado 953 Adm 1., Ensenada,Baja California22830, M•xico ROBERTO CARMONA, UniversidadAut6noma de Baja CaliforniaSur, Departa- mentode Biolog•aMarina, Carretera al SurKm 5, La Paz, BajaCalifornia Sur 23090, M•xico

Ojo de Liebre (Scammon's)Lagoon, on the west coast of the Baja California peninsula,is surroundedby saltmarshesand saltfiatsexposed to periodic tidal inundation.Part of theseareas was modifiedin 1956 by the buildingof saltworks,a systemof managedponds covering 27,773 ha. Theseponds contain several islands, sandbars, and sand fiats suitable for nestingbirds (Figure 1). In 1996 we surveyedthe saltwork•snesting birds, as part of a year-roundstudy (Carmona and Danemann 1998). Thesesaltworks lie next to Ojo de LiebreLagoon and southof GuerreroNegro, a smallindustrial town in the northwesternportion of the state of Baja CaliforniaSur, in Mexico(Figure 1). The salt-productionprocess involves the pumpingof seawater from the lagooninto a systemof concentrationponds, where it evaporatesthrough the actionof the sun and wind. Water levelsand salinityare kept fairlystable at all times, as a requirementfor the process. The area,which is part of E1Vizca•noReserve of the Biosphere,is concessionedto Exportadorade Sal S.A.C.V., a joint venture of the Mexican governmentand a foreigncorporation. All accessto the area is restricted,and occasionalvisitors are escortedin companyvehicles. As a result, the saltworkis the only portion of the reserveto receiveeffective protection from human intrusion. The birdsof Ojo de Liebre Lagoonhave been studiedsince 1927. Masseyand Palacios(1994) reported15 speciesbreeding in the lagoon,13 of whichhad been previouslyobserved by Bancroft(1927). Otherreports for the area(Kenyon 1947a,b, 1949, Castellanoset al. 1994, and Castellanosand Ortega 1995) madeno additions to the list of birdsbreeding in the lagoon. We performed12 monthlycensuses in the saltworks,from December1995 to December 1996; there was no censusin October.During censuseswe carried out detailedinspections of all areassuitable for nesting,by foot and/or usingbinoculars (8x and 10x) and a spottingscope (15-60x). Sandbars and sandfiats were reached by road, while a motor boat was usedto visitislands in areasS1-A, 8, and 9 (Figure 1). The poor conditionof someof the pathwaysand dikes made visiting the coastto the southand eastof the concentrationponds impossible. Each survey required two days,covering 18,117 ha, equivalentto 65.2% of the saltworks.We recordedten speciesbreeding in the saltworks. Osprey(Pandion haliaetus).We recorded24 activenests, 20 of them built on artificialplatforms, three on otherstructures (tank tower, power post, and lighthouse tower), and one on Salicornia bushes.Ten nests were located on the road to E1 Chaparritochannel (including the one on Salicorniabushes), 13 alongthe channel, and one in the Salitralespumping station, in a postright over the pumps.The birds' breedingseason here in 1996 extendedfrom Januaryto June, with the highest numberof activenests observed during March (24 nests).From their surveyof the lagoonand the saltworks,Castellanos and Ortega (1995) reporteda total of 126

WesternBirds 31:195-199, 2000 195 NOTES

OF PACIFIC CAUFORNIA OCEAN

--GUERRERO NEGRO

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oJo DE LIEBRE

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Figure1. Saltworksnext to Ojo de LiebreLagoon, Baja CaliforniaSur, M•xico. The evaporationponds are indicatedby numbers.The pondsvisited during this studyare shaded.

196 NOTES pairs, 13 of them withinthe saltworks.According to thosefigures and our own data, the saltworkshold between10 and 19% of the localbreeding population. PeregrineFalcon (Falco peregrinus). We observedone nest,active in Marchand April, on a light tower in E1 Chaparritochannel. The same nest was noted by Castellanoset al. (1994) in 1993. This speciesis enlistedas endangeredby Mexican law (Gobiernode los EstadosUnidos Mexicanos 1994). SnowyPlover (Charadrius alexandrinus). We foundtwo nests (each one with one egg)in June, on a sandflat besideArea 1. There may havebeen more, sincewe saw at least20 adultsin the area.Additionally, in Augustwe foundthree chicks on another sandflat, besideArea 8. The SnowyPlover is a commonresident on bothcoasts of the peninsula,nesting on sandybeaches between March and July (Wilbur 1987, Howell andWebb 1995), and wasreported nesting previously in the saltworksby Masseyand Palacios(1994). AmericanOystercatcher (Haematopus palliatus). We found one nest with two eggsin April, on a sandbar in Area 8. This speciesis a commonresident on both coastsof the peninsula(Wilbur 1987, Howell and Webb 1995) and has beenlong reportedas a breederin the area (Bancroft1927, Kenyon1949). Gull-billedTern (Sterna nilotica). We foundfour nestsand sevenadults in June, on a sandyislet in Area S1-A. Eachnest contained two eggs.The nestsconsisted of shallowhollows in the sand, and all of them containedpieces of shell.We saw no nestingactivity in July,suggesting that breeding might not have been successful. This isthe first breeding record for the speciesin theBaja California peninsula. The closest Gull-billedTern colonyis locatedin the Gulf of Californiaon MontagueIsland, in the Coloradoriver delta, 500 km north of GuerreroNegro (Palaciosand Mellink 1992, Peresbarbosa1995). CaspianTern (Sterna caspia).This speciesnested in two areasof the saltworks. Onewas on a sandyislet in Area 8, whichin Junehad 15 nests(13 of themwith only oneegg). In Julythis colony was abandoned. The othercolony shared an isletin Area S1-A withthe Gull-billedTerns. In June,this colony had 37 nestscontaining from one egg to newly hatchednestlings, while in July it held 20 activenests and 23 well- developednestlings. The CaspianTern was reportedpreviously nesting in Ojo de Liebrelagoon by Bancroft(1927) and in thesesaltworks by Masseyand Palacios (1994). Royal Tern (Sterna maxima). We found the first nestsof this speciesin May, sharinga sandyislet in Area8 withthe CaspianTern colony. The colonyhad 23 nests, mostwith onlyone egg.In Junewe observed99 nests(17 with two eggs),but in July the colonywas completelyabandoned. This specieswas firstnoted breeding in the saltworksby Masseyand Palacios(1994). LeastTern (Sterna antillarum). We foundfive nestsin June, on the samesand fiat besideArea 1 usedby the Snowy Plover.Nests contained one or two eggs.This species,listed as endangered (Gobiernos de losEstados Unidos Mexicanos 1994), had beenpreviously reported breeding in Ojo de LiebreLagoon by Bancroft (1927) andin the saltworksby Masseyand Palacios(1994). BlackSkimmer (Rynchops niger). We foundeight nests in June,with the Caspian and the Gull-billedTerns, on a sandyislet in Area S1-A. The nestshad two or three eggs.In Julythe colonyhad grown to 22 nestswith eggs, 85 adults,and 13 nestlings. This is the firstbreeding record for the BlackSkimmer on the peninsula.The species hasbeen recorded in Baja CaliforniaSur (Palaciosand Alfaro 1992, Carmonaet al. 1995), butthe closestbreeding colony is located on MontagueIsland, in the Colorado River delta (Palaciosand Mellink 1994, Peresbarbosa1995). SavannahSparrow (Passerculus sandwichensis). We foundtwo nests(one with one egg,the otherwith one egg andtwo nestlings)in May, on a sandyislet in Area 8, andanother (with two eggs)on an isletnearby. Nests were builtin Frankenia bushes.

197 NOTES

We countedtotals of 24 and 15 adultson those islets. Ojo de LiebreLagoon is the type localityof subspeciesP.s. anulus. Severalcharacteristics of the saltworksenhance their use as breedinghabitat for birds.According to the informationprovided to usby the Exportadorade Sal biology department(J. C. Peralta pers. comm.), physicaland chemicalconditions of the evaporationponds are stablewithin each pond and throughtime, this beinga basic requirementof the salt-productionprocess. This stabilitypromotes the growth of diversefish and marineinvertebrate communities, which provide an abundantand densefood resource for birds.Shallowness of the pondsmakes prey easy to spotand catch.Also, the saltworkarea is currenfiy protected by Exportadorade Sal.This limits humantransit and preventsany alterationof the birds'breeding habitat, as well as the extractionof prey speciesof economicvalue (i.e., fish, shrimp,and brine shrimp). The largenumbers of residentand migratorybirds using the area (Carmonaand Danemann, 1998), togetherwith its useas a breedingarea, suggeststhe Guerrero Negro saltworksare a functional,diverse, and high-qualitybird habitat. We thankthe CompafifaExportadora de SalS.A.C.V. fromGuerrero Negro, and particularlyJulio C•sar Peralta,director of the Biologyand EnvironmentalImpact Department,for the logisticsupport of thisresearch. Fernando Heredia shared with us his experiencefrom yearsobserving birds at the saltworks.Saudiel Ramirez and FelipeBecerril assisted during field work. Philip Unitt andWilliam T. Everettprovided valuablereview of the manuscript.This note is contribution32 of Afegua, the Associationfor the Study and Conservationof the Birds of the Baja California Peninsula.

LITERATURE CITED

Bancroft,G. 1927. Breedingbirds of Scammon'sLagoon, Lower California. Condor 29:29-27. Carmona, R., and Danemann, G. 1998. Avifauna del h•bitat generado por el desarroliosalinero en ias adyacenciasde la LagunaOjo de Liebre, B. C. S. Ciencias Marinas 24:389-408. Carmona, R., Fernandez,G., Brabata,G., and Arvizu, E. 1995. Variaci6ntemporal en ia abundanciadel rayador, Rynchops niger (Charadriiformes: Laridae) en Baja CaliforniaSur, M•xico. Rev. Biol. Trop. 43 (1-3):313-315. Castellanos,A., Salinas,E, and Ortega,A. 1994. Statusand reproductionof the PeregrineFalcon at a coastalLagoon in Baja CaliforniaSur, Mexico. J. Raptor. Res. 28:110-112. Castellanos,A., and Ortega,A. 1995. Artificialnesting sites and ospreysat Ojo de Liebre and GuerreroNegro Lagoons,Baja CaliforniaSur, Mexico. J. Field Ornithol. 66: 117-127. Gobiernode los Estados Unidos Mexicanos 199•. Normaoficial mexicana NOM- 059-ECOL-1994, que determinalas especiesy subespeciesde flora y fauna silvestres,terrestres y acu•ticasen peligrode extinci6n,amenazadas, raras y las sujetasa protecci6nespecial, y queestablece especificaciones para su protecci6n. Diario Oficialde la Federaci6n,16 mayo 1994, pp. 1-60. Howell, S. N. G., and Webb, S. 1995. A Guideto the Birdsof Mexicoand Northern Central America. Oxford Univ. Press,Oxford, England. Kenyon,K. 1947a. Breedingpopulations of the Ospreyin LowerCalifornia. Condor 49:152-158. Kenyon,K. 1947b. Noteson the occurrenceof birdsin Lower California.Condor 49:210-211.

198 NOTES

Kenyon,K. 1949. Observationson behaviorand populationsof Oyster-catchersin Lower California. Condor 51:193-199. Massey,W. B., andPalacios, E. 1994. Avifaunaof the wetlandsof BajaCalifornia, Mexico: Current status. Studies Avian Biol. 15:45-57. Palacios,E., andAlfaro, L. 1992. Occurrenceof BlackSkimmers in BajaCalifornia. W. Birds 23:173-176. Palacios,E., and Mellink,E. 1992. Breedingbird recordsfrom MontagueIsland, northern Gulf of California. W. Birds 23:41-44. Palacios,E., andMellink, E. 1994. Additionalbreeding birds records from Montague Island,northern Gulf of California.W. Birds24:259-262. Peresbarbosa,R. E. 1995. Fluctuacionesespaciales y temporalesde las avesque anidanen IslaMontague, Golfo de California,Mexico. M. S. thesis,CICESE, Ensenada,Baja California,M•xico. Wilbur,S. R. 1987. Birdsof BajaCalifornia. Univ. of Calif.Press, Berkeley.

Accepted21 February2000

Least Tern Sketch by Jamie NI. Chavez

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