Migratory shorebirds in the Saltworks, , 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 ,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), 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 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,

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 winters of 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 10 Willet Catoptrophorussemipalmatus 1,000 SemipalmatedPlover Charadriussemipalmatus 9 Ruddy TurnstoneArenaria interpres 400 American OystercatcherHaematopus palliatus 6 Black-neckedStilt Himantopusmexicanos 340 Wilson's Plover Charadrius wilsonia 6 Greater Yellowlegs Tringa melanoleuca 220 Wilson's PhalaropePhalaropus tricolor 5 Black-bellied Plover Pluvialis squamrola 220 Least SandpiperCalidris minutilla 2 LesserYellowlegs Tringa fiavipes 200 Wandering Tattler Heterocelus incanus 1 Red PhalaropePhalaropus fulicaria 170 Black OystercatcherHaematopus bachmani 1

Minimum shorebird abundance for 1996 = 110,500 of the hypersalinecondition of the saltworksduring fall, its American A vocet and Black-necked Stilt spring migration routes are probably offshore (Paulson 1993). Bearingin mind the well-knownhalophylic habits of American Avocets were more abundant than the Black- the phalaropes(Jehl 1988), our findings suggestthat this neckedStilts in all seasons.Avocets were presentyear round, locationcould be the mostimportant stopover for the species with the highestnumber in winter,while stiltswere predomi- on the Mexican Pacific coast. nantlywinter residents and were absentin summer(Table 1). Both speciesare morecommon on the eastcoast of the Gulf Sandpipers of California than on the peninsula(Morrison et al. 1992, Engilis et al. 1998). Five sandpiperspecies were recorded at the saltworks:West- em Sandpiper,Dunlin, Sandefiing,Red Knot,and Least Sand- Willets piper. Of these,Western Sandpipersand Dunlins were the mostabundant, while Sanderlings,Red Knotsand Least Sand- Presentyear round, with highestnumbers in winter(Table 2). pipersgenerally numbered less than 100 individuals(Table 1). The winter populationat the saltworksaveraged around 300, WesternSandpipers were most abundantin winter; their andwas comparablein sizeto that of La Paz Bay (Carmona secondhighest abundance was recordedin fall (southward 1995), while the east coast of the Gulf of California has a migration) and lowest abundancein spring (northward winter populationof 5,000-8,000, mainly in the Colorado migration) (Table 2, Fig. 2). This patternis similar to that River delta (Mellink et al. 1997, Morrison et al. 1992). foundin La Paz Bay, on the southeastcoast of the peninsula (Fernfindezet al. 1998), but differs from that found in Cali- Yellowlegs fornia, USA (Page et al. 1979), where the speciesshows a peak abundanceduring spring. GreaterYellowlegs were slightlymore abundantthan Lesser Dunlins were most abundantin spring(Table 2, Fig. 2). Yellowlegs(1.1:1). Both speciesshowed fall migrationpeaks This peak may relateto northwardpassage of birdswinter- of 220 and 200 birdsrespectively (Table 2). Southwardmi- ing further southalong the peninsula.Dunlins winteringin gratoryflocks of thesespecies in La Paz Bay usuallydo not Baja California are from the pacifica race, that has a re- exceed 30 individuals (Carmona 1995). strictedwinter range from the west coastof Canadato the Baja CaliforniaPeninsula (Warnock & Gill 1996). Tumstones

Marbled Godwit The occurrenceof thesespecies in the saltworkswas spor- adic. When present,Ruddy Tumstones were generallymore This specieswas presentyear round,with peak abundance abundantthan Black Tumstones(Table 1). The samepattern during winter (Table 2). More than 90% of the Marbled was found in La Paz Bay (Carmona 1995). Godwitsobserved in the saltworkswere roosting; they prob- ably fed on the nearbymudflats of the Ojo de LiebreLagoon Plovers (Morrison et al. 1992, Page et al. 1997). Four speciesof ploverswere recorded:Black-bellied Plover Dowitchers (= Grey Plover), Snowy Plover (= Kentish Plover), Semi- palmated Plover, and Wilson's Plover (Table 1). Black- These specieswere most abundantduring fall (southward bellied Ploverswere mostabundant during springmigration, migration),with lowernumbers in winter(Table 2). Dowitch- but were also presentduring fall and summer(Table 2). ershave beenreported in La Paz Bay in much smallernum- Snowy Ploversbreed in the saltworks(Danemann & Car- bers (<200, Carmona 1995). There, migratory fluctuations mona 2000). We found two nests(each one with one egg) on were not as greatas thoserecorded at the saltworks. a sand flat beside Area 1, and three chicks on another sand

Bufferin 97 April 2002 Danemann: Migratoryshorebirds in the Guerrero Negro Saltworks 39

70000 - (a) RED-NECKED PHALAROPE 60000

50000

z 4OOOO

30000

20000

10000

nc

r 1 i D J F M A M J J A S O N D 300001 (b) WESTERN SANDPIPER 25000

20000

15000

10000

5OOO

D J F M A M J J A S O N D

140001 (c) DUNLIN 12000

10000 LU

8OOO c• z 6000 m 4OOO 2000 no/ i i i i m I f i i D J F M A M J J A S O N D

Fig. 2. Monthlycounts of (a) Red-neckedPhalaropes, (b) WesternSandpipers and (c) Dunlins(the three most abundant species) at the GuerreroNegro Saltworks during December 1995 to December1996 (nc = no countwas made in October).

Bulletin 97 April 2002 40 Wader Study Group Bulletin flat, besideArea 8 (Fig. 1). This specieswas mostnumerous portedfor the easterncoast of the Gulf of California(Mellink in summerand wasnot observedin winter. Only smallnum- et al. 1997) and California, USA (Page et al. 1979), where bers of Semipalmatedand Wilson's ploverswere recorded, the greaterconcentrations of shorebirdsoccur during spring never more than 15 of either species. (northward) migration. However, all areas show that the southwardmigration is more protracted in time than the Long-billedCurlew northwardmigration (Helmers 1992, Paulson1993). A featureof shorebirdmigration at GuerreroNegro is the Maximum numbersoccurred during fall migration(40 indi- difference in the numbersrecorded between the fall (south- viduals), a smaller populationremained in winter and the ward) and spring (northward)migrations. It appearsthat in specieswas also present in spring.Similar patterns of occur- the fall high numbersof shorebirdsmigrate southward along rence have been reported for the Colorado River Delta the Baja California Peninsulabefore stopping or crossingto (Mellink et al. 1997) andLa PazBay (Carmona1995). At the the mainland,while mostof them migratenorthward along latter site, flocks of up to 200 have been seen. the Sonora-Sinaloa(mainland) coast in spring.This might particularly be the casefor Western Sandpiper,which in Whimbrel springoccurs in relativelylow numbersat GuerreroNegro, but in high numbersin the ColoradoRiver Delta (Sonora) Present during fall migration, but more abundantduring and in Santa Maria Bay (Sinaloa) (Mellink et al. 1997, winter, when we observed 32 individuals. Engilis et al. 1998). The over-summeringpopulation in Guerrero Negro of Oysterca tchers Marbled Godwits was 22% of that found during winter (basedon the highestcount for each season).For American American Oystercatcherswere not abundant,but present Avocets this number was 19%, for Willets 16%, and for during winter and summer,when we recordedthree breed- Western Sandpipers6%. Hockey et al. (1998) suggestthat ing pairs(Danemann & Carmona,2000). Black Oystercatch- larger shorebirdspecies may require more than a year to ers were rare and only observedduring winter. mature,and subadultsmay remainin winteringareas. There- fore, a greaterpercentage over-summering might be expected Wandering Tattler in largerthan smallerspecies. This is what we observedin the saltworksand suggeststhat the area may be particularly We observedonly one individual, duringthe winter. importantfor youngbirds, enabling them to surviveand im- prove their foragingefficiency during summer. Migratory chronology Importance of the Guerrero Negro saltworks as a The seasonalpresence of shorebirdsin the GuerreroNegro habitat for shorebirds saltworksfollows the general migratory pattern shown by nearcticshorebirds (Myers et al. 1987, Paulson1993). This The saltproduction process at GuerreroNegro generatesan comprisesa winteringperiod (December to February),with artificial habitat with relatively stable food availability a minimum count of 34,200 (calculatedfrom the sum of the throughtime and protectionfrom humandisturbance (Car- highestnumbers recorded for each speciesduring winter), mona& Danemann1998). The pondsprovide food for small spring(northward) migration (March to April), with a mini- shorebirdslike Red-neckedPhalarope, Western Sandpiper mum countof 27,800, summer(May to June),with a mini- andDunlin (i.e. brinefly Ephydraspp., brine shrimpArtemia mum countof 3,000, andfall (southward)migration (July to spp., polychaete worms as Platynereis and Palola, and November), with a minimum count of 91,800. This pattern amphipods,isopods and alpheidcrustaceans), and roosting is comparableto that observedin La Paz Bay (Carmona areasfor larger species,like Marbled Godwit. Thesecharac- 1995, Fernandez et al. 1998), but is different from that re- teristicsmake the GuerreroNegro saltworks one of the most important habitats for shorebirdson the Baja California Table 2. Relative abundance of shorebirds in the Guerrero Negro Peninsula,only surpassedin termsof shorebirdabundance Saltworks by season. A = peak abundance (>90% of year's high- by the Ojo de Liebre and San Ignacio (Massey & est count), B = high abundance (50-90% of the year's highest Palacios 1994, Morrison et al. 1992, Page et al. 1997), and count), C = low abundance (10-50% of the year's highest count), possiblyby the MagdalenaBay lagooncomplex, the largest D = marginaloccurrence (<10% of the year's highestcount). wetlandof the peninsula,which has still notbeen thoroughly studied. In 2000, in recognition of their significance, the Species Winter Spring Summer Fall GuerreroNegro Saltworkswere declareda "Site of Interna- tional Importance"by the WesternHemisphere Shorebird Red-neckedPhalarope D D D A ReserveNetwork (B. Harrington,Manomet Center for Con- Western Sandpiper A C D B Dunlin C A D C servationSciences, Massachusetts, USA, pers. comm.). Dowitchers C D D A Marbled Godwit A C C C ACKNOWLEDGEMENTS American Avocet A C C C Willet A B C C We are grateful to S. Ram/rez, F. Becerril, R. Carmona,E. Ruddy Turnstone A C D D Lozano and M. Rivera for assistance in the fieldwork. We Black-necked Stilt A B D C thank the CompafiiaExportadora de Sal, S.A. de C.V., of GreaterYellowlegs C D D A GuerreroNegro, in particularJulio Cdsar Peralta, at thattime Black-bellied Plover D A C C head of the Department of Biology and Environmental LesserYellowlegs D C D A Impact,for logisticalsupport. The manuscriptwas improved

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