NOTES

OBSERVATIONS ON ESTEROS EL AND LA BOCANA, BAJA SUR, MEXICO, IN SEPTEMBER 1991

GUSTAVO D. DANEMANN and ROBERTO CARMONA, Departamento de BiologiaMarina, UniversidadAut6noma de Baja CaliforniaSur, Apartado 19-B, La Paz, Baja CaliforniaSur 23000, M•xico

The coastof the southernVizcaino Desert, Baja CalifomiaSur, includesthree lagoons:La Bocana,El Coyote, and San Ignacio(Figure 1). The avifaunaof La Bocanaand San Ignaciolagoons was first described by Huey (1927). Sincethen, the onlyornithological research in the area hasbeen by Reithermanand Storrer (1981), Danemann(1991), and Danemannand Guzmbn (1992), who studiedvarious aspects of the avifaunaof San IgnacioLagoon. No ornithologicalinformation from La Bocanaor El Coyotehas been publishedsince Huey's early account. In September1991 we surveyedEl Coyote and La Bocana lagoons,usually referred as "esteros."Here we summarizeobservations recorded during those surveys. El Coyote (alsoknown as La Escondida),located between 26ø48 ' and 26ø50' N, and 113ø24' and 113ø29' W, hastwo main armsthat reachdepths from 2 to 4 m and is separatedfrom the ocean by a narrow sand bar. The shorelineof the lagoon consistsof sandbeaches (along the bar), mud fiats, mangroves,and salt marshes. Mostof the lagoonis coveredby mangroveislands separated by narrowchannels. In the open areasof the lagoon,low tidesexpose large shoals.Human activitiesin El Coyoteinclude some commercial and sportfishing, mainly in the deeperchannels. EsteroLa Bocana,known to Huey (1927) as Pond Lagoon, is locatedbetween 26ø42' and 26ø47' N, and 113ø34' and 113ø42' W. It is a narrowlagoon separated from the oceanby a sandbar extendingnorthwest-southeast. Averaging 600 m, its widthranges from 150 to 1250 m. Thisestero holds some mangrove islands and salt marshes,and its shorelineincludes sand beachesalong the bar, and mud fiats, marshes,and mangrovesalong the mainlandcoast. Both lagoonsare includedin the "El Vizcaino"National Reserve of the Biosphere (Gobiernode los EstadosUnidos Mexicanos 1988). We surveyedEstero El Coyotefrom 8 to 12 September1991, La Bocanaon 13 and 14 September1991. We usedan inflatable7-foot boat that allowedus to cover mostof the lagoons,including the shallowchannels among the mangroves.Observa- tionsduring low tidewere madefrom the shoreor mudfiats. We used10x binoculars and a 40x spottingscope. We recorded45 speciesin [] Coyote(EC) and 36 in La Bocana(LB), for a total of 47 speciesover both areas. MagnificentFrigatebird (Fregata rnagnificens). EC, 3 juveniles.The nearestcolony is at Santa MargaritaIsland, Magdalena Bay. BrownPelican (Pelecanus occidentalis). EC, 1300 to 1500; LB, severalgroups of fewer than 30 individualseach. No evidenceof nesting. Double-crestedCormorant (Phalacrocorax auritus). EC, 200 to 250; LB, a few groupsup to 30 individualseach. Black-crownedNight Heron (Nycticoraxnycticorax). EC, 3 ad., 1 juv.; LB, 2 ad. Yellow-crownedNight Heron (N. violaceus).EC, 13 ad., 3 juv.; LB, 1 ad. Green-backedHeron (Butoridesstriatus). EC, 14; LB, 2. TricoloredHeron (Egretta trico/or). EC, 11; LB, 5. Little Blue Heron (E. caerulea).EC, 11 ad., 1 juv. ReddishEgret (E. rulescerts).EC, 14; LB, 6. SnowyEgret (E. thula). EC, 39; LB, 5. WesternBirds 24:263-266, 1993 263 NOTES

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Great Egret(Casmerodius albus). EC, 1. Great Blue Heron (Ardea herodias). EC, 17; LB, 10. White-facedibis (Plegadis chihi). EC, 1. White Ibis (Eudocimusalbus). EC, 15 ad., 3 juv,; LB, 4. Localfishermen reported large concentrations of ducksand geese,especially the Brant(Branta bernicla),in both EC and LB duringthe winter.We sawno waterfowl duringour visit. SemipalmatedPlover (Charadrias semipalmatus). LB, 3. SnowyPlover (C. alexandrinus).EC, 11; LB, 2. Wilson'sPlover (C. wilsonia).EC, 5; LB, 3. Black-belliedPlover (Pluvialis squatarola). EC, 15; LB, 1. MarbledGodwit (Limosafedoa). EC, 900 to 1200; LB, 1000. Willet (Catoptrophorussemipalmatus). EC, 150 to 300; LB, 100. Dowitchers(Limnodromus sp.). EC, 500 to 600; LB, 1000. Whimbrel(Numenius phaeopus). EC, 16; LB, 1. Long-billedCurlew (N. americanus).EC, 26; LB, 16. GreaterYellowlegs (Tringa melenoleuca).EC, 23; LB 68. SpottedSandpiper (Actiris macularia). EC, 1; LB, 1. Red-neckedPhalarope (Phalaropus Iobatus). EC, 2; LB, 1. RuddyTurnstone (Arenaria interpres).EC, 1; LB, 4. Sanderling(Calidris alba). EC, 38. WesternSandpiper (C. mauri). EC, 2000; LB, 200. LeastSandpiper (C. minutilla). EC, 200. Heermann'sGull (Larus heermanni). EC, 53; LB, 1. Ring-billedGull (L. delawarensis).EC, 16; LB, 29. WesternGull (L. occidentalis).EC, 30; LB, 16. ElegantTern (Sternaelegans). EC, 800 to 850; LB, 400. RoyalTern (5. maxima).EC, 100 to 120, including2 fledglings;LB, 13. Forster'sTern (Sternaforsteri). EC, 7; LB, 12. LeastTern (5. antillarum). EC, 12 ad., 5 juv. CaspianTern (5. caspia).EC, 14; LB, 3. Osprey(Pandion haliaetus). EC, 12; LB, 15. BeltedKingfisher (Ceryle alcyon). EC, 3. Horned Lark (Eremophilaalpestris). EC, 20; LB, 12. NorthernRough-winged Swallow (Stelgidopteryx serripenis). EC, 12. Common Raven (Corvuscorax). EC, 2. LoggerheadShrike (Lanius ludovicianus). EC, 7; LB, 1. NorthernMockingbird (Mimus polyglottos). LB, 1. MangroveWarbler (Dendroica petechia castaneiceps). Common in mangrovesof both lagoons. SavannahSparrow (Passerculus sandwichensis). EC, S; LB, 3. Mostof the speciesreported by Huey (1927) were presentduring our visit.The most importantdifference was the absenceof waterfowl,of which Huey noted severalspecies during his mid-April visit but had not arrivedby our earlySeptember visit. Thirty-sevenof the 52 speciesreported for San IgnacioLagoon (Danemann and Guzm•n 1992) were observedin E1Coyote and/or La Bocana.The highsimilarity of the avifaunaof theselagoons reflects their physicalsimilarities: absence of perma- nentfresh water flow, high rate of tidalflushing, possessing extensive shores and mud fiats, and similarvegetation and climate.Differences in bird diversitybetween El Coyoteand La Bocanaare presumablya result of the largersize and more extensive habitat of the former. Giventheir position along the Pacific flyway, suitability of habitat,and the numbers of migratoryshorebirds recorded during our visit,these esteros may be considered

265 NOTES important areas for these species,and probablyfor waterfowl. IncludingOjo de Liebre (Scammon's)and San Ignacio, this group of coastallagoons should be includedin anyresearch and conservation program regarding migratory birds in . This researchwas supportedby the SeabirdProgram coordinated by Dr Juan R. Guzm•n Poo at the UniversidadAut6noma de Baja CaliforniaSur, througha grant from the Secretaria de Educaci6n Pgblica de M•xico. Kodak of M•xico donated the film usedin the research.Philip Unitt greafiyassisted in editingthis paper.

LITERATURE CITED

Danemann,G. D. 1991. Amplitudy sobreposici6nde nichoseco16gicos de aves icti6fagasanidantes en Isla Ballena,Laguna San Ignacio,Baja CaliforniaSur. Thesis,Universidad Aut6noma de BajaCalifornia Sur, La Paz. Danemann,G. D., and Guzm•n-Poo,J. R. 1992. Noteson the birdsof San Ignacio lagoon,Baja California Sur, M•xico. W. Birds23:11-19. Gobiernode los EstadosUnidos Mexicanos. 1988. Decretopor el que se declarala Reservade la Bi6sfera"El Vizcaino," ubicada en el Municipiode Muleg•, B.C.S. Diario de la Federaci6n 1729(22):2-27. Huey, L. 1927. The birdlife of San Ignacioand Pondlagoons on the westerncoast of Lower California. Condor 29:239-243. Reitherman,B., and Storrer, J. 1981. A preliminaryreport on the reproductive biologyand ecology of theWhale Island Osprey (Pandion haliaetus) population, San IgnacioLagoon, Baja CaliforniaSur, M•xico. Unpublishedreport to the WesternFoundation of VertebrateZoology, 1100 GlendonAve., Suite 1407, ,CA 90024, U.S.A.

Accepted21 April 1993

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