Migratory Shorebirds in the Guerrero Negro Saltworks, Baja California Sur, Mexico GUSTAVOD
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Migratory shorebirds in the Guerrero Negro Saltworks, Baja California Sur, Mexico GUSTAVOD. DANEMANN*j, ROBERTOCARMONA 2 & GUILLERMOFERN/[.NDEZ 3'* • PronaturaNoroeste-Mar de Cortes.Apartado 953 Adm 1., Ensenada,Baja California,CP 22830, M•xico, e-maihgdanemann @pronaturanw. org; 2Universidad Autdnoma de Baja CaliforniaSur, Departamentode Biolog[aMarina. Carretera al SurKm 5, La Paz, BajaCalifornia Sur, CP 23090, M•xico;3 Centro de Investi- gacidn Cientfficay de EducacidnSuperior de Ensenada. Km 107 Carretera Tijuana-Ensenada,Ensenada, Baja California, M•xico Danemann,G.D., Carmona,R. & Fernfindez,G. 2002. Migratory shorebirdsin the GuerreroNegro Saltworks, Baja CaliforniaSur, Mexico. WaderStudy Group Bull. 97: 36-41. This studydescribes the speciescomposition, seasonal abundance, and migration chronology of shorebirdsat the GuerreroNegro Saltworks,an artificialhabitat located at the mid pointof the Baja CaliforniaPeninsula, Mexico. Censuses of shorebirds were carried out once a month from December 1995 to December 1996. We recorded26 shorebirdspecies. Taking the highest monthly record for eachspecies, the estimated minimum abun- dancein the studyperiod was 110,500birds. Red-necked Phalaropes Phalaropus lobatus and Western Sand- pipersCalidris mauri were the mostabundant. Seasonally abundance varied between winter (Decemberto Feb- mary, mean= 31,600 birds/month),spring migration (March to April, mean= 15,800birds/month), summer (May to June,mean = 1,900birds/month), and fall migration(July to November,mean = 44,300 birds/month). This patternis similar to that observedin La Paz Bay in the southof the peninsula,but contrastswith that ob- servedon the easterncoast of the Gulf of California,where greaternumbers of shorebirdsoccur during spring migration.Our resultsindicate that the GuerreroNegro saltworksis one of the mostimportant habitats for migratoryshorebirds along the Baja CaliforniaPeninsula, surpassed only by the Ojo de Liebreand San Ignacio coastallagoons. INTRODUCTION STUDY AREA AND METHODS Shorebirdsbreeding in the Arctic andinterior regions of the The GuerreroNegro saltworksare locatednext to the Ojo de United Statesand Canadamigrate to their winteringgrounds Liebre (Scammon's)Lagoon, southof GuerreroNegro, a using severalflyways. The Pacific Flyway runs along the small industrialtown in the northwestof the stateof Baja western side of America and includesthe Baja California California Sur, Mexico (Fig. 1). Peninsula,where major shorebirdwintering grounds have re- Salt productioninvolves pumping seawaterfrom the cently been identified (Massey & Palacios1994, Morrison lagoonthrough a systemof concentrationponds, where it et al. 1994, Page et al. 1997). However, most studieshave evaporatesthrough the action of the sun and wind. These focusedon the northand south parts of the peninsulaand data pondscover 27,773 ha, andinclude islands, sand bars, mud arelimited in seasonality,area surveyed, and species covered flats,and shallow water areas used by shorebirdsto roostand (Palacios et al. 1991, Carmona 1995, Mellink et al. 1997, feed. Water levels and salinity are kept fairly stableat all Fernfindez et al. 1998). times, as a requirementof the industrialprocess. The first This studydescribes the speciescomposition and seasonal pondsof the system(S 1-A and 1 in Fig. 1) receivewater abundancepatterns of shorebirdsat the Guerrero Negro pumpedfrom Ojo de Liebre Lagoon and their salinitiesare saltworks (also known as "salinas"), a man-made habitat in similar to that of the lagoonat around33 ppt (L6pez Cort6s the middleof the westcoast of the Baja CaliforniaPeninsula. 1991). Shorebirdsmake use of even the most salineponds This research,the first to be carried out for the whole of one in the system,where salinity reaches 250 ppt. The pondsare completeyear in this part of Baja California,increases our separatedby dikes,which are mostly drivable. understandingof shorebirdmovements along the peninsula The area, which is part of the "El Vizca/no" Biosphere duringnorthward and southwardmigration. It alsoallows a Reserve,is concessionedto Exportadorade Sal (ESSA), a first evaluationof the importanceof this artificial habitatas joint ventureof the Mexican governmentand a foreigncor- a stopoverfor migratoryshorebirds. poration.All accessto the area is restricted. * Correspondingauthor ** Currentaddress: Department of BiologicalSciences, Simon FraserUniversity, Burnaby, British ColumbiaV5A 1S6, Canada Bulletin 97 April 2002 36 Danemann: Migratory shorebirdsin the Guerrero Negro Saltworks 37 (8x and 10x) and spottingscopes (15-60x). We calculated the abundanceof a speciesin any given month as the sum of our counts and estimates for all parts of the study area. Scientificnames of all speciesmentioned are given in Table 1. In planningour censuses, we did nottake into accounttide levels in the nearby Ojo de Liebre Lagoon. As a conse- quence,our shorebirdcounts show fluctuations that may not be wholly theproduct of migratorypatterns, and may include variation arising from daily movementsbetween the salt- works and the lagoon.To identify migratorypatterns, we divided the year into four seasons:winter (December-Feb- ruary), spring/northwardmigration (March-April), summer (May-June), and fall/southwardmigration (July-Novem- Negro ber). To each period we assignedthe highest number re- corded for each speciesin any of the monthly censuses. Crystallizafic•'•------__•ran•n. •lar Then, we ratedeach period with an A for abundances>90% r•ghwa• of theyear' s highestrecord for the species(peak abundance), B for abundancesfrom 50 to 90% of the year's highestrecord (high abundance),C for abundancesfrom 10 to 50% of the year'shighest record (low abundance),and D for abundances <10% of the year's highestrecord (marginal occurrence). This allowed us to comparerelative abundancesper season throughthe year. Estero Norte We estimatedtotal numbersthrough the year andby sea- sonby consideringonly the highestmonthly count for each species.In this way, we avoidedmultiple countsof birds -5 27o48'- stayingin the areamore than one month. The resultis a con- OJO DE LIEBRE servative estimate, as it does not take into account either LAGOON Pumping Station turnover or tide-related movements between the saltworks and Ojo de Liebre Lagoon. RESULTS AND DISCUSSION Pumping Station Shorebird abundance During the year, we recorded26 shorebirdspecies using the saltworks with a minimum estimate of 110,500 individuals (Table 1). 6 km Shorebirdsurveys carded out during the wintersof 1992, ' ' S-2 1993 and 1994 at the Ojo de Liebre-GuerreroNegro Lagoon complex(Morrison et al. 1992, Page et al. 1997) estimated 114o11 ' I populationsof 267,983, 128,710,and 275,391 birds,respec- tively. Our highestwinter numbersat the saltworksindicate Fig. 1. The Guerrero Negro Saltworksand Ojo de Liebre Lagoon, a minimum population of 34,200 shorebirds, or 12.4 to Baja CaliforniaSur, Mexico.The concentrationponds surveyed from 26.6% of the totalsestimated for the entire lagooncomplex December 1995 to November 1996 are shaded. They are also num- duringthe wintersof 1992-1994. bered accordingto a scheme used by the managers of the saltworks Red-neckedPhalaropes and Western Sandpipers were the (S-1A, S-lB, and I to 9). mostabundant species, followed by Dunlins,dowitchers, and Marbled Godwits. Except for the high numbersof phala- The saltworkswere surveyedusing a vehicleprovided by ropes,the relativeabundances of shorebirdswere compara- ESSA, whichtravelled along established routes. There were ble to other areasin northwestMexico (Morrison et al. 1992, two limitations:(1) it wasnot possible to visit areasserviced Mellink et al. 1997, Pageet al. 1997, Engilis et al. 1998). by roadsand dikes in bad condition,and (2) it was not pos- sible to visit the saltwork shores located south and east of the Species accounts concentrationponds, as there are no roadsin thoseareas. Shorebird censuses were carried out once a month from Red-necked Phalarope December1995 to December1996, except for October1996 when no count was made. Owing to the large size of the On the basis of its seasonaloccurrence in the study area studyarea,two dayswere requiredto completeeach census. (peakabundance in fall andonly marginaloccurrence for the Flocks smallerthan 300 individualswere counteddirectly, restof the year (Table 2, Fig. 2), we considerthis speciesas while the size of larger flocks was estimated using the a fall migrant.During fall, it is found in higher numbersin methoddescribed by Pageet al. (1979), following the sug- Guerrero Negro than anywhere else in coastal California gestionsmade by Kasprzyk& Harrington(1989) to stand- (Pageet al. 1979) or the Baja CaliforniaPeninsula (Morrison ardizeestimations. Observations were madeusing binoculars et al. 1992, Page et al. 1997). Although it takes advantage Bulletin 97 April 2002 38 Wader Study Group Bulletin Table 1, Maximumcounts of shorebirdspecies at the Guerrero Negro Saltworksduring December 1995 to November 1996. The minimum shorebirdabundance for the year is calculatedby summingthe maximumcounts for all species. Species Maximum count Species Maximum count Red-neckedPhalarope Phalaropus lobatus 58,000 Black TurnstoneArenaria melanocephala 60 Western SandpiperCalidris mauri 18,200 SanderlingCalidris alba 60 Dunlin Calidris alpina 13,000 Long-billed Curlew Numeniusamericanus 40 Dowitchers Limnodromusspp. 12,000 Whimbrel Numeniusphaeopus 32 Marbled Godwit Limosafedoa 5,400 Snowy Plover Charadriusalexandrinus 19 American Avocet Recurvirostra americana 1,100 Red Knot Calidris canutus