Studies in Avian Biology No. 15:45-57, 1994.
AVIFAUNA OF THE WETLANDS OF BAJA CALIFORNIA, MBXICO: CURRENT STATUS
BARBARA W.MASSEY AND EDUARDO PALACIOS
Abstract. Although Baja California has not experienced loss of wetlands comparable in magnitude to that in California, some habitat changes have provoked changes in the abundance and distribution of wetland avifauna. The Osprey population has increased in the Vizcaino wetlands, but at least three species of egrets and herons, and American Oystercatcher have declined due to human disturbance. The Elegant Tern is missing at Laguna Ojo de Liebre, but there is a new colony at Delta de1 Rio Colorado. Several species have expanded their range into Baja California and have established breeding colonies, e.g., Little Blue Heron, Laughing Gull, Caspian, Royal, Forster’s and Gull-billed terns, and Black Skimmer. Both number and variety of breeding birds have increased in Laguna San Ignacio. At least 52 species of water-associated birds breed in the several habitats of the wetlands, including five endangered or threatened species. The northernmost breeding colony of the Magnificent Frigatebird is located in Bahia Magdalena. Migratory birds use the wetlands in large numbers; the biggest con- centrations of shorebirds are found in two wetlands-Laguna Ojo de Liebre and Delta de1 Rio Colorado. The lagoons of Baja California are the primary wintering grounds for Brant. Mangroves in the southern wetlands have recently been identified as wintering habitat for passerines. Threats to the wetlands are primarily from resort and industrial developments being planned by international companies. Con- servation of these vital avian habitats is a matter of concern to all ornithologists.
Key Words: Mkxico; Baja California; coastal wetlands; marsh avifauna; endangered species; distri- bution; conservation.
The peninsula of Baja California, MCxico scant literature. In 1987 Wilbur compiled extends 1600 km south from Tijuana to an annotated checklist from the literature Cabo San Lucas. Its diverse natural habitats and from reliable field observers (Wilbur include richly vegetated deserts, riparian 1987); his bibliography was comprehensive valleys, rugged mountain ranges and the and allows us to concentrate on data gath- magnificent coastal wetlands whose avifau- ered subsequently. Recently there has been na is our subject. Long insulated from dis- an accelerated interest in documenting turbance and development by lack of roads, numbers and species in Baja California, and the wetlands were also out of reach to all much of the information presented here has but the hardiest ornithologists prior to the not been published heretofore. Scientific opening of the peninsula-long highway in names of species are given in Table 1. 1974. Post-highway changes have been The first attempt at estimating numbers gradual but inexorable and today some of of birds in Baja California was in 1949 when the major wetlands are under threat, par- the U.S. Fish and Wildlife Service (USFWS) ticularly from tourist-oriented develop- added the peninsular lagoons to its aerial ment. However, most are still in near-pris- surveys of Mexican waterfowl (Sanders and tine condition, and presumably have not Sanders 198 1). Since 1974 the surveys have experienced the changes in bird use that have been a cooperative project with the Mexican characterized Californias’ wetlands. Unfor- government. Brant have received special at- tunately, numerical baseline data are tention and have been censused every year sketchy, as early ornithologists reported even when the all-Mtxico surveys were re- species ’ presence and breeding information, duced to every 3rd year (U.S. Fish and but seldom numbers. Wildlife Service unpublished reports on The first checklist of the birds of Baja winter waterfowl surveys of the Mexican California appeared in 1889 (Bryant 1889), West Coast and Baja California, 1954-l 992, and in the 1920s Bancroft (1927a, b) and available from J. Voelzer, USFWS, Port- Grinnell (1928) added extensively to the land, OR).
45 46 STUDIES IN AVIAN BIOLOGY NO. 15
In 1977 the Osprey population of west THE WETLANDS coast mainland Mexico and Baja California Figure 1 shows the locations of the major was censused (Henny and Anderson 1979). wetlands; most are complexes of marshes The survey was repeated in 1992-1993 (C. with connecting waterways. We will focus Henny, pers. comm.). on the seven largest: 1) Ester0 de Punta Ban- The first attempt at obtaining numerical da, 2) Bahia San Quintin complex, 3) Ojo data on a marsh bird was the 198 1 census de Liebre complex, 4) Laguna San Ignacio of the Light-footed Clapper Rail in the two complex, 5) Bahia Magdalena complex, 6) northern wetlands, Ester0 de Punta Banda Ensenada de La Paz and 7) Delta de1 Rio and Bahia San Quintin (Zembal and Massey Colorado. 198 1). Four more censuses were done in Small saltmarshes on the west coast not 1986-1988 (available from R. Zembal, dealt with here are La Salina, La Mision, USFWS, 2730 Loker Ave West, Carlsbad, San Antonio de1 Mar, and San Gregorio. CA 92008). Laguna Percebu, a 5 km long, narrow salt- Regular shorebird censusing of the north- marsh on the northeast coast deserves spe- ern estuaries was begun in 1989 as part of cial mention as it hosts many breeding birds the Point Reyes Bird Observatory (PRBO) including Wilsons’ Plover and California Pacific Flyway Project in cooperation with Least Tern (see Table 1). Freshwater marsh- pro esteros,a bi-national, non-profit group es are extremely rare on the peninsula; ex- dedicated to protection of Baja Californias’ amples are La Lagunita Formex-Ibarra in wetlands and Centro de Investigation Cien- Ensenada, La Bocana de Santo Domingo, tifica y de Education Superior de Ensenada, El Rosario, San Ignacio, Ester0 de San Jose B.C. (CICESE), a Mexican research and de1 Cabo, La Poza de Todos Santos and teaching institution. Comprehensive counts Mulege. Others are without names and have been done 2-3 times a year at the known only to local residents, e.g., a series northern estuaries since 1989 (Page et al. of ponds several kilometers inland from 1992); in 1991 and 1992 all of the other Puerto Lopez Mateos. major wetlands were visited by members of the above organizations, and numbers of Ester0 de Punta Banda wintering and breeding birds documented. Area: 2100 ha. A description of this Additional information on Ensenada de La northernmost estuary can be found in Iba- Paz and Isla Margarita in Bahia Magdalena rra-Obando (1990). Thousands of shore- has come from studies by students at Uni- birds winter here, the most important nu- versidad Autonoma de Baja California Sur merically is the Marbled Godwit (Palacios (UABCS). et al. 199 1). Many species of wintering wa- In 1992 the Canadian Wildlife Service terfowl have been documented; American (CWS) began a Mexican Shorebird Atlas Wigeon is the most numerous, numbering Project in conjunction with the Mexican in the thousands (E. Palacios, pers. obs.). government. Estimates of wintering shore- The California Least Tern and Light-footed bird numbers in western Mexico were made Clapper Rail (U.S. and Mexico endangered by aerial survey in early 1992, the first of a species), Snowy Plover (U.S. threatened 3-yr series (Morrison et al. 1992). species), and Beldings’ Savannah Sparrow All of the large estuaries in Baja Califor- (California endangered species) breed here. nia host thousands of migrating and win- tering shorebirds and waterfowl. They also provide breeding habitat for raptors, rails, Bahia de San Quintin complex terns, gulls, cormorants, pelicans, fiigate- Area: 12,060 ha. Descriptions are given birds, herons, egrets, shorebirds, and sev- in Ibarra-Obando (1990) and Palacios and eral passerines. Alfaro (1991). Vast eel grass beds (Zostera BAJA CALIFORNIA WETLANDS--Massey and Palacios 41
FIGURE 1. The peninsula of Baja California, Mexico, showing locations of the major wetlands. 1) Ester0 de Punta Banda; 2) Bahia San Quintin complex (north to south-Laguna Figueroa, Bahia San Quintin); 3) Ojo de Liebre complex (Laguna Manuela, Guerrero Negro, Ojo de Liebre); 4) Laguna San Ignacio complex (La Bocana, El Coyote, San Ignacio, Ester0 el Delgadito); 5) Bahia Magdalena complex (Laguna Santo Domingo, Bahia Magdalena, Bahia Almejas); 6) Ensenada de La Paz; and 7) Delta de1 Rio Colorado. 48 STUDIES IN AVIAN BIOLOGY NO. 15 marina) in the channels attract >20,000 tebrates and fish and thus for birds. Caspian Brant in winter. On recent winter surveys and Royal terns nest on an island in one of up to 27,000 shorebirds have been counted the cells; California Least Terns breed in on the extensive mudflats (Page et al. 1992). scattered colonies around another. Snowy The above-mentioned four threatened or Plovers nest on saltpans throughout the salt- endangered species of birds also nest here. works. Thousands of Red-necked and Wil- Salt ponds along the coast just north of the sons’ phalaropes are present during July and bay also attract shorebirds. August in the saltworks close to Ocho Bom- Approximately 15 km north of Bahia de bas; thousands of Eared Grebes and hun- San Quintin but not connected to it is La- dreds of Red Phalaropes are present in win- guna Figueroa, a hypersaline flat 20 km long ter (F. Heredia, pers. comm.). Over 270,000 that lies behind very tall dunes and has no shorebirds (Morrison et al. 1992) and ocean outlet. After winter storms it is cov- >35,000 Brant (Conant et al. 1992) winter ered with water and attracts thousands of here. shorebirds, particularly Western Sandpi- pers (L. Stenzel, pers. comm.). The Snowy Plover, Caspian Tern, Forsters’ Tern, and Laguna San Ignacio complex California Least Tern have nested here (Pa- Several small esteros lie north and south lacios and Alfaro 199 1). In 1992, however, of Laguna San Ignacio, which covers ap- the local community diverted three rivers proximately 28,000 ha (Contreras 1988), to impound water in the basin, and heavy and lies in a NE/SW direction with the ocean winter rains created a lake up to two meters entrance on the south end (Fig. 1). This la- deep, transforming shorebird habitat into goon complex marks the northern limit of waterfowl habitat. The future of this area as red mangrove (Rhizophora mangle), which breeding habitat is uncertain. begins to replace saltmarsh as one moves south and becomes the dominant plant in Ojo de Liebre complex Bahia Magdalena (Roberts 1989). White Three lagoons are included in this group: Ibis, Little Blue Heron and other species of Laguna Manuela (600 ha), Guerrero Negro wading birds nest in the mangroves. Two (2100 ha), and Ojo de Liebre (36,600 ha) islands provide nesting habitat for Brown (Contreras 1988). All empty into Bahia Viz- Pelican, Double-crested Cormorant, Os- caino, all have vast areas of saltmarsh, mud- prey, Reddish Egret, Caspian and Royal flat and extensive barrier beaches. Several terns, Snowy Plover, American Oyster- small islands in Laguna Ojo de Liebre pro- catcher and others (Danemann and Guz- vide breeding habitat for raptors and sea- man Poo 1992; E. Palacios and L. Alfaro, birds. Double-crested Cormorant, Osprey, pers. obs.). The bay is a major wintering site Peregrine Falcon, American Oystercatcher, for Brant (> 33,000) (Conant et al. 1992) Wilsons’ Plover, Western Gull, California and shorebirds (32,000) (E. Palacios, pers. Least Tern, and several species of herons obs.). and egrets breed on Islote La Piedra; Isla Concha has breeding colonies of Double- Bahia Magdalena complex crested Cormorant, Osprey, Western Gull, This vast complex of bays, dunes, islands Caspian Tern, Royal Tern, and several spe- and mangrove stands extends 250 km along cies of herons and egrets. On the southeast the southwestern shore of Baja California. side of Laguna Ojo de Liebre a huge salt- A series of long, narrow dune islands pro- works is divided into cells, most of which tects it against the sea for most of its length, are hypersaline, but several cells (close to with ocean openings between them. At the Ocho Bombas, where sea water is pumped south end is the mountainous, 40 km long into the system) provide habitat for inver- Isla Santa Margarita. A mangrove lagoon BAJA CALIFORNIA WETLANDS-Massey and Palacios 49 on its protected southwest side hosts the AVIFAUNA continents’ northernmost breeding colony The coastal wetland avifauna of Baja Cal- of Magnificent Frigatebirds. Brown Pelican ifornia is dominated, at least numerically, and Brandts’ Cormorant breed on Isla Santa by large numbers of Anseriformes, Ciconi- Margarita in large numbers (Amador 1985, iformes, and Charadriiformes. Only at Ba- Everett and Anderson 199 1); in winter their hia Magdalena is the dominant avifauna populations are further augmented by mi- Pelecaniformes. At all sites, avian popula- grants. Other breeding birds in Bahia Mag- tions increase considerably in winter, when dalena are Double-crested Cormorant, sev- large numbers of waterfowl and shorebirds eral species of heron and egret, Snowy and congregate to feed and rest in such areas. Wilsons’ Plover, American Oystercatcher, Table 1 is a checklist of the birds of Baja and California Least Tern. A population of Californias’ wetlands as of January 1993, the Scrub Jay is resident in the mangroves which includes all species seen within the (Pitelka 195 1; M. Evans and S. Howell, pers. past five years. Sources are recent publica- comm.; B. W. Massey, pers. obs.). tions (Danemann and GuzmLn Poo 1992; Erickson 1992; Everett and Anderson 199 1; Ensenada de La Paz Howell and Webb 1992, 1993; Morrison et al. 1992; Page et al. 1992; Palacios and Al- This 4500 ha shallow lagoon is connected faro 1991, 1992a, b; Palacios et al. 1991; to Bahia de La Paz by a canal. Its mudflats, Palacios and Mellink 1992) and the obser- mangroves and recently created dredge-fill is- vations of Lucia Alfaro, Edgar Amador, Jose lands provide habitat diversity. Wilsons’ Plo- Angel Sanchez, Michael Evans, Salvador ver, Yellow-footed Gull, California Least Tern Gonzalez, Fernando Heredia, Steve How- and several species of heron and egret breed ell, Barbara Massey, Renato Mendoza, Leo- there. Brown Pelican, White Pelican, Yellow- poldo Moreno, Eduardo Palacios and Lynne footed Gull and a variety of shorebirds are Stenzel. abundant in winter (E. Palacios, pers. obs.). Breeding birds are designated by an as- terisk and only recently documented breed- Delta de1Rio Colorado ing (since 1985) is acknowledged; several Once a vast wetland, the Colorado River species that bred historically (e.g., Virginia delta (240,000 ha) has only a remnant stream Rail, Sora, and Common Yellowthroat) have emptying into the Gulf of California as the no recent documentation. There may also result of dams and water diversion along be omissions of casually-occurring species. the river in both U.S. and Mexico. There MIGRATORY BIRDS are, however, extensive mudflats at the land/ gulf interface, which support > 163,000 Although the USFWS census of wintering wintering shorebirds, principally small waterfowl in Mexico has included Baja Cal- “peep” sandpipers (Morrison et al. 1992) ifornias’ wetlands for the past 40 years, the and thousands of waterfowl, especially Pin- principal surveyors state that an aerial sur- tail (Kramer and Migoya 1989). Ester0 Rio vey done every few years at different tide Colorado and Marismas Nacionales on the levels and under various weather conditions mainland are the first sites in Mexico to be gives results far too variable to show statis- designated reserves in the Western Hemi- tically analyzable changes (James Voelzer, sphere Shorbird Reserve Network. Isla Bruce Conant, pers. comm.). While changes Montague, a low, flat and sparsely vegetated in waterfowl numbers may be undocu- island at the mouth of the delta, provides mentable, survey data show that most wa- breeding habitat for herons and seabirds, terfowl winter in the wetlands of mainland including the California Least Tern (Pala- Mexico rather than in Baja California, with cios and Mellink 1992). the exception of Brant (Conant et al. 1992). 50 STUDIES IN AVIAN BIOLOGY NO. 15
TABLE 1. CHECKLIST OF BIRDS OF THE BAJA CALIFORNIA WETLANDS
Scientific name Common name Where foundt
Gavia stellata Red-throated Loon 1 Gavia pacifica Pacific Loon 2, 5 Gavia immer Common Loon l-3,5 Tachybaptus dominicus* Least Grebe 10* Podilymbus podiceps* Pied-billed Grebe 1, 2, 6, lO* Podiceps auritus Homed Grebe 2 Podiceps nigricollis Eared Grebe l-8,10 Aechmophorus occidentalis Western Grebe l-7. 10 Aechmophorus clarkii Clarks’ Grebe 2,3; 5, 10 Fulmarus glacialis Northern Fulmar l-3 Sula dactylatra Masked Booby 5, 6 Sula nebouxii Blue-footed Booby 5,6 Sula leucogaster Brown Booby 6 Pelecanus erythrorhynchos White Pelican 1,3-7 Pelecanus occidentalis ’ Brown Pelican l-3,4*, 5*, 6-10 Phalacrocorax auritus* Double-crested Cormorant 1, 2, (3-5)*, 6, 7, 10 Phalacrocorax penicillatus ’ Brandts’ Cormorant 1, 3,4, 5*, 6, 7, 10 Fregata magniJicens* Magnificent Frigatebird 4, 5*, 6, 8, 10 Botaurus lentiginosu.? American Bittern 2,4 Ixobrychus exilis ’ Least Bittern 4, 7* Ardea herodias* Great Blue Heron 1, 2, (3-5)*, (7-9)*, 10 Casmerodius albus* Great Egret 1,2, (3-6)*, 10 Egretta thula+ Snowy Egret 1, 2, (3-7)*, 8-10 Egretta caerulea* Little Blue Heron 1-3, 4*, 5*, 6, 10 Egretta tricolor* Tricolored Heron 1, 2, (3-6)*, 8 Egretta rufescens ’ Reddish Egret 2, (3-6)*, 8 Bubulcus ibis* Cattle Egret 1, 2, 5, 6*, 7*, 10 Butorides virescens* Green Heron 1) (4-7)*, 9* Nycticorax nycticorax* Black-crowned Night-Heron 1, 2, (3-7)* Nycticorax violaceus ’ Yellow-crowned Night-Heron (3-6)* Eudocimus albus* White Ibis (4-6)* Plegadis chihi White-faced Ibis 6, 10 Mycteria americana Wood Stork 6 Anser albtfrons Greater White-fronted Goose 1-4 Anser caerulescens Snow Goose 1, 2, 10 Branta bernicla Brant l-5.8 Branta canadensis Canada Goose Anas platyrhynchos Mallard 1-3, 6, 9, 10 Anas acuta Northern Pintail 1-7, 10 Anas discors Blue-winged Teal 1, 2 Anas cyanoptera Cinnamon Teal 1-3, 5, 6, 9, 10 Anas clypeata Northern Shoveler 1-3, 5, 6, 9, 10 Anas strepera Gadwall 1-3, 5 Anas americana American Wigeon l-4,9 Aythya valisineria Canvasback l-4 Aythya americana Redhead l-5, 10 Aythya collaris Ring-necked Duck 14.10 Aythya marila Greater Scaup 1-4; 6, 10 Aythya a&is Lesser Scaup l-5,6, 10 Melanitta nigra Black Scoter 1, 2 Melanitta perspicillata Surf Scoter 1-5 Melanitta fusca White-winged Scoter 14 Bucephala albeola Bufflehead 1-6, 10 Mergus merganser Common Merganser 4, 5 Mergus serrator Red-breasted Merganser 1-8, 10 Oxyura jamaicensis ’ Ruddy Duck l-6,9, lO* Cathartes aura Turkey Vulture l-10 Pandion haliaetu? Osprey l-10 (3,4, 5, 6, 8)* Elanus leucurus White-tailed Rite 1,2,5 Haliaeetus leucocephalus* Bald Eagle 5* Circus cyaneus Northern Harrier l-4,9 BAJA CALIFORNIA WETLANDS--Massey and Palacios 51
TABLE 1. CONTINUED
Scientific name Common name Where foundt
Buteo regalis Ferruginous Hawk l-3 Falco sparverius American Kestrel 1,2, 5, 6, 9 Falco columbarius Merlin 1,6 Falco peregrinus* Peregrine Falcon 1,2, 3*, 4*, 569, 10 LateraNus jamaicensis Black Rail Rallus longirostris* Clapper Rail ;1-9,* Rallus limicola Virginia Rail 1,2,4,7 Porzana Carolina Sora 2, 5, 7, 10 Gallinula chloropu? Common Moorhen 7*, 10* Fulica americana* American Coot 2, 3,6, 7*, 9, 10* Pluvialis squatarola Black-bellied Plover l-10 Charadrius alexandrinus* Snowy Plover (l-5)*, 6, 7, 9*, 10 Charadrius wilsonia+ Wilsons’ Plover 1, 2, (3-6)*, 8*, 9*, 10 Charadrius semipalmatus Semi-palmated Plover (l-lo)* Charadrius voctferus* Killdeer l-10 Charadrius montanus Mountain Plover Haemotopus paNiatus* American Oystercatcher t;l6)* Haemotopus bachman? Black Oystercatcher 1, 2, 3*, 4* Himantopus mexicanus* Black-necked Stilt 1, 2*, 3-6, 7*, 8, 9*, 10 Recurvirostra americana* American Avocet 1, 2*, 3-6, 7*, 8, 9* Tringa melanoleuca Greater Yellowlegs l-10 Tringa jlavipes Lesser Yellowlegs l-10 Catoptrophorus semipalmatus Willet l-10 Heteroscelus incanus Wandering Tattler l-6, 10 Actitis macularia Spotted Sandpiper l-6, 9, 1 Numenius phaeopus Whimbrel l-10 Numenius americanus Long-billed Curlew l-10 Limosa fedoa Marbled Godwit l-10 Arenaria interpres Ruddy Tumstone l-10 Arenaria melanocephala Black Tumstone l-5, 6, 1 Calidris canutus Red Knot 1,2,5 Calidris alba Sanderling l-10 Calidris mauri Western Sandpiper l-10 Calidris minutilla Least Sandpiper l-10 Calidris bairdii Bairds’ Sandpiper 3 Calidris melanotos Pectoral Sandpiper 1,2 Calidris alpina Dunlin l-10 Limnodromus griseus Short-billed Dowitcher l-10 Limnodromus scolopaceus Long-billed Dowitcher l-10 Phalaropus tricolor Wilsons’ Phalarope l-3 Phalaropus lobatus Red-necked Phalarope l-3 Phalaropus fulicaria Red Phalarope l-10 Larus atricilla* Laughing Gull 3, 5, 6, 7*, 8, 10 Larus Philadelphia Bonapartes’ Gull 1-6, 10 Larus heermanni Heermanns’ Gull l-10 Larus canus Mew Gull 1 Larus delawarensis Ringed-billed Gull l-10 Larus californicus California Gull l-6, 10 Larus argentatus Herring Gull l-3, 5 Larus thayeri Thayers’ Gull l-3 Larus livens* Yellow-footed Gull 4, 5, 6*, 10 Larus occidentalis ’ Western Gull 1) 2, (3-5)* Larus glaucescens Glaucous-winged Gull 1 Larus hyperboreus Glaucous Gull 1, 5 Xema sabini Sabines’ Gull 4, 10 Sterna nilotica ’ Gull-billed Tern 7*, 8 Sterna caspia* Caspian Tern 1, (2-q*, 5-10 Sterna maxima* Royal Tern 1, 2, 3*, 4*, 5, 6, 7*, 8-10 Sterna elegans* Elegant Tern l-6,7*, 8-10 Sterna hirundo Common Tern 10 Sterna forsteri* Forsters’ Tern 1,2*, 3-10 52 STUDIES IX AVIAN BIOLOC-Y NO. 15
TABLE 1. CONTINUED
Saentilic name Common name Where found?
Sterna antillarum* Least Tern (l-lo)* Chlidoniasniger Black Tern 1,3 Rynchopsniger* Black Skimmer l-4,6, I* Zenaida asiatica* White-winged Dove 6*, 10 Zenaida macroma* Mourning Dove 6*, 9, 10 Athene cunicularia* Burrowing Owl (l-l)* Asiojlammeus Short-eared Owl 1,2 Chordeilesacutipennis* Lesser Nighthawk 6* Ceryle alcyon Belted Kingfisher 1-6, 10 Eremophila alpestris* Homed Lark (Id)* Aphelocomacoerulescens* Scrub Jay 5* Corvuscorax Common Raven l-10 Anthus rufescens American Pipit 14 Lank ludovicianus Loggerhead Shrike 2-6 Dendroicapetechia* Yellow (Mangrove) Warbler (4-6)* Geothlypistrichas Common Yellowthroat 2, 10 Geothlypisbeldingi Belding’s Yellowthroat Passer&us sandwichensis* Savannah Sparrow f P-6)* * Denotesrecently documented breeding. t Numbersin this columnrefer to the wetlandsdescribed m the sectionWETLANDS. Locations1-7 are shown in Figure 1; locations8-10 are noted in the text but not shownin the figure. I = Esterode Punta Banda,2 = Bahia San Qumtin complex,3 = LagunaOjo de Llebre complex,4 = San lgnaciocomplex, 5 = Bahia Magdalenacomplex, 6 = Ensenadade La Par, 7 = Delta de1Rio Colorado,8 = LagunaPercebB, 9 = Small saltmarshes, 10 = freshwaterponds/marshes.
Brant receive special attention, as they (Morrison et al. 1992; Page et al. 1992; E. winter almost exclusively on the Pacific coast Palacios, pers. obs.). The first Canadian of the U.S. and Mexico. In 1952 an inven- Wildlife Service aerial survey in 1992, which tory that accounted for approximately 90% covered the west coast of mainland Mexico of the population showed that two-thirds of and Baja California, documented the im- the birds were in Baja California, the rest portance of the peninsular wetlands for in the U.S., mainly in the bays of California shorebirds. The combined count at Laguna (Sandersand Sanders198 1); there were none Ojo de Liebre complex and Delta de1 Rio on the Mexican mainland. In 1958 Brant Colorado (434,000) was more than half of were first seen in the wetlands of Sonora- the total number (800,000) seenon the sur- Sinaloa and by 1990 represented 15% of the vey (Morrison et al. 1992). total in Mexico (Conant et al. 1990). The The mangrove stands in the southern California population declined concurrent- wetlands host many wintering passerines ly as coastal wetlands were lost to devel- that nest in North America. The importance opment, and in 1990 85% of the total pop- of this habitat throughout Mexico has only ulation was wintering in Mexico, primarily been recognized recently (S. Howell, pers. in the Baja California lagoons. Brant num- comm.). Species seen in the mangroves at bers have shown wide fluctuations over the Bahia Magdalena are Solitary Vireo, Or- past 20 years, but “declines” were regularly ange-crowned Warbler, Yellow-rumped followed by “recoveries,” and in 13 of the Warbler, Black-and-white Warbler, Oven- 20 years the numbers were between 100,000 bird, Northern Waterthrush, Painted Bun- and 130,000 (USFWS winter waterfowl sur- ting, and Black-throated Sparrow (Amador veys of Mexico). 1985; M. Evans, S. Howell, pers. obs.). Baja California’s coastalwetlands are ma- jor wintering sites for shorebirds. Combin- BREEDING BIRDS ing recent counts from three different Fifty two species of birds now breed in sources,we estimate that 5 10,000 individ- the coastal wetlands of Baja California (Ta- uals winter in the wetlands of the peninsula ble 1). Six species, previously undocu- BAJA CALIFORNIA WETLANDS--Massey and Palacios 53
TABLEZ. ESTIMATEDNUMBEROFPAIRSOFBIRDSBREEDINGINTHEBAJACALIFORNIAWETLANDS, 1985-1992
Number of pairs in the wetlands EPB* BsQ LOL LSI BM ELP DRC Brown Pelican 1100 3000 Double-crested Cormorant 3500 500 250 Brandts’ Cormorant 300 Magnificent Frigatebird 20,000 Great Blue Heron 5 12
* Abbreviatmns of the wetlands: EPB = Estcro de Punta Banda. BSQ = Bahia San Qumtin, LOL = Laguna Ojo de Liebre, LSI = Laguna San Ignacio, BM = Bahia Magdalena, ELP = Ensenada de La Paz, DRC = Delta de1 Rio Colorado. t Cabfomia Least Terns also nested at Laguna Percebfi (46-76 prs).
mented, have well established breeding col- link 1993). The birds’ current status in the onies: Little Blue Heron, Cattle Egret, U.S. was recently summarized (Collins et Laughing Gull, Gull-billed Tern, Forsters’ al. 1991). Tern and Black Skimmer. Table 2 shows Two former breeding species, Northern the number of pairs and locations of all nest- Harrier and Sora, have not been docu- ing species documented since 198 5. Brandts’ mented recently; the harrier probably no Cormorant was formerly known to breed longer nests in Baja California (Pete Bloom, only on offshore islands; there are now sev- pers. comm.); the Sora is presumably still eral small colonies (So-100 pairs each) on present in freshwater marshes and has been Santa Margarita Island in Bahia Magdalena overlooked. The uncommon Black Rail was (Amador 1985; E. Palacios, pers. obs.). The a breeding bird in Bahia San Quintin in the range of the Elegant Tern also appears to be 1920s (Wilbur 1987) but then not docu- shifting. Early in the century a few pairs mented anywhere in Baja California until were reported nesting in Laguna Ojo de recently, when two or three individuals were Liebre (Bancroft 1927a), but there has been heard calling in Bahia San Quintin in Feb- no recent nesting there. A new colony has ruary 1991 (Erickson 1992). One endemic recently formed on Isla Montague in the species, Beldings’ Yellowthroat, breeds ex- Colorado River Delta (Palacios and Mel- clusively in the freshwater marshes of the 54 STUDIES IN AVIAN BIOLOGY NO. 15
TABLE3. HABITATPREFERENCESOFBREEDINGBIRDS peninsula from Mulege south (Howell and INTHEBAJACALIFORNIAWETLANDS Webb 1992).
Beach- Salt- Fresh- Breeding habitat in Baja Californias’ wet- es/ marsh water salt- vege- marsh Man- Is- lands generally falls into four categories: Rats tation veg. groves lands beaches and saltflats, saltmarsh vegetation, Least Grebe X freshwater marsh vegetation, and mangrove Pied-billed Grebe X stands. The islands in the lagoons often have Brown Pelicant X Double-crested several of these habitats; and some, e.g., Isla Cormorantt x x Ballena in Laguna San Ignacio, also have Brandts’ Cormorantt X scrubby desert vegetation that provides nest Magnificent Frigatebirdt x x American Bittern X sites for seabirds and wading birds. While Least Bittern X some bird species are strictly island nesters, Great Blue Heron x x many others nest both on islands and the Great Egret x x Snowy Egret x x mainland, wherever there is suitable habi- Little Blue Heron X tat. Table 3 categorizes the habitat prefer- Tri-colored Heron x x ences of the 52 breeding species. Reddish Egret x x Cattle Egret X Green Heron x x DISCUSSION Black-crowned Night- Although Baja California has not expe- Heron x x Yellow-crowned Night- rienced loss of wetlands comparable in mag- Heron x x nitude to that documented for California, White Ibis X some habitat changes have occurred. The Ruddy Duck X Osprey X most altered wetland along Baja Califor- Bald Eagle X nias’ Pacific coast is Laguna Ojo de Liebre, Peregrine Falcon X site of the worlds’ largest saltworks (20,000 Clapper Rail X X Common Moorhen X ha). The area had previously been mostly American Coot X saltmarsh and salt flats subject to periodic Snowy Plover X X tidal inundation (Nelson 1921). The only Wilsons’ Plover X X Killdeer X preconstruction numerical baseline data are American Oystercatcher X X found in Bancroft (1927a) who estimated Black Oystercatcher X X numbers of some of the breeding birds. The Black-necked Stilt x x American Avocet x x changes between 1927 and the present are: Laughing Gull? X the American Oystercatcher declined from Yellow-footed Gull? about 150 pairs in 1926 to 30 in 1991; the Western Gull? X Gull-billed Tern? X small Elegant Tern colony (6 pairs) is miss- Caspian Tern X X ing; the Snowy Egret decreased from > 100 Royal Tern? X X to 20 pairs; the Tricolored Heron declined Elegant Tern? X Forsters’ Tern X X from >75 to about 20 pairs; the Black- Least Tern X crowned Night-Heron dropped from 100 to Black Skimmer X X 50 pairs. Herons and egrets that used to nest White-winged Dove X Mourning Dove X in the marshes are now found nesting only Burrowing Owl X on islands, mainly due to increased human Lesser Nighthawk X disturbance by fishermen and tourists. The Homed Lark X Scrub Jay X populations of other breeding species have Yellow (Manarovej remained stable (Caspian, Royal and Least Warbier - ’ X terns, Western Gull) or increased (Osprey Beldings’ Yellowthroat X Savannah Sparrow X and Double-crested Cormorant). Double- t Breeds only on islands in Baja Califomxt. crested Cormorant numbers in Laguna Ojo de Liebre rose from 80 pairs in 1926 (Ban- BAJA CALIFORNIA WETLANDS-Massey and Pufucios 55 croft 1927a) to 3500 in 1984 (J. A. Sanchez, established on Isla Ballena, a site of little pers. comm.). ornithological interest early in the century It is impossible to quantify changes in (Huey 1927). numbers of most migratory species over the Current plans to construct the worlds’ past century for lack of baseline data. Some largest solar salt evaporation pond system may have experienced changes due to loss at Laguna San Ignacio (J. Bremer, pers. of breeding grounds (e.g., Marbled Godwit comm.) could increase the winter popula- and Willet); others may have shifted to Baja tion size of several shorebird species in this California when wintering habitat else- area, since the plan calls mainly for the where was lost (Brant). flooding of usually dry playa that has lim- One species that has been reasonably well ited habitat value for shorebirds. tracked is the Osprey, particularly in the Several species have expanded their range Vizcaino wetlands (Laguna Ojo de Liebre into Baja California. The Black Skimmer complex, Laguna San Ignacio complex). In has recently established nesting colonies in 1927 Bancroft found a “dozen or more southern California, and at Isla Montague nests” restricted to the islands in the Laguna in Delta de1 Rio Colorado, so nesting is like- Ojo de Liebre complex (Bancroft 1927a); ly also in Ester0 de Punta Banda and Bahia Kenyon (1947) visited the islands in May San Quintin, where the bird is a year-round of 1946 and found 27 occupied nests; Jehl resident (Palacios and Alfaro 1992b). The (1977) estimated the lagoon population at Cattle Egret is now found along the length 25 pairs in 1957, 30 pairs in 1970, and 20 of the peninsula and breeds at Ensenada de pairs in 197 1. During the 1970s the popu- la Paz (E. Palacios, pers. obs.). The Pacific lation began to increase. In 1977 the pop- coast population of Caspian Terns has in- ulation estimate was 27 pairs for the islands creased since the mid-1960s and they have and 50 pairs for the whole complex (Henny colonized new nesting sites at Lagunas Fi- and Anderson 1979); in 1980 Castellanos gueroa and San Ignacio (Palacios and Alfaro (1982) reported 7 1 active nests; and in 1984 1992a). The Little Blue Heron colony in Salinas-Zavala et al. (199 1) reported 76 Laguna San Ignacio (150 pairs) is the first breeding pairs. breeding record of this heron in Baja Cali- While several factors may be involved in fornia, although it may also breed in the the increase in Osprey numbers, including mangroves of Bahia Magdalena and Ense- reduction of DDT in the environment, a nada de La Paz. major factor was a reversal in attitude by The coastal wetlands of the peninsula lie local residents. Protection of the Osprey is within a transition zone between temperate now an accepted fact in Guerrero Negro. and tropical climates, and draw species from Ospreys are no longer shot by fishermen, both. The northern breeding limits of the and dozens of nesting poles have been erect- Magnificent Frigatebird, Tricolored Heron, ed in the town and on islands in the lagoons. Reddish Egret, Yellow-crowned Night-Her- In 1992, at least 15 of these towers were in on, White Ibis, Wilsons’ Plover and Amer- use (L. Alfaro, M. Evans, B. Massey, E. Pa- ican Oystercatcher are found in Baja Cali- lacios, pers. obs.). fornia (Table 1). On the Pacific coast, none Although tourism and commercial fish- of these species breeds north of the Ojo de ing have increased in recent years in Laguna Liebre Lagoon complex (28th parallel). San Ignacio, so have the number and variety Conversely, the peninsula is the southern of breeding birds (Danemann and Guzmin end of the breeding range for Bald Eagle, Poo 1992). Colonies of Brown Pelicans (1100 Snowy Plover, Black Oystercatcher, Amer- breeding pairs), Double-crested Cormo- ican Avocet and Forsters’ Tern (Table 1). rants (500 pairs), Caspian Terns (150 pairs) The wetlands provide a portrait of Cali- and Royal Terns (350 pairs) have become fornias’ coastal marshes as they were before 56 STUDIES IN AVIAN BIOLOGY NO. 15 their wholesale damage and destruction. and is encroaching on the remainder. In Ba- They offer an opportunity to observe the hia Magdalena, a foreign construction com- behavior and breeding biology of water-as- pany has bought 80,000 ha of land with the sociated birds in unaltered marsh habitat, purpose of building a hotel, golf course, ma- such as the endangered Light-footed Clap- rina, and other recreational facilities. In- per Rail and Beldings’ Savannah Sparrow. dustrial development is another threat. At Equally unchanged are the islands in the Bahia San Quintin exploitation of the vol- lagoons that provide breeding sites for a great canic rock from the cinder cones is under variety of species. The California Least Tern consideration by foreign investors. A phos- and Snowy Plover nest on ocean-fronting phoric rock extraction plant and a ther- beaches and other natural habitats; in only moelectric plant have been constructed and a few instances have Least Terns been found are operational in Bahia Magdalena; their on dredge-spoil islands or other man-made impacts on the bay have not been assessed. habitats in Baja California. In 199 l-l 992 a The wetlands of Baja California are an survey documented over 500 pairs at 28 ecological treasure of international impor- breeding sites throughout the peninsula (E. tance. Their integrity is of concern to all Palacios and L. Alfaro, pers. obs.). ornithologists. A cooperative international The recent surge of field work has filled effort to insure their conservation is an im- many gaps in our knowledge, but there is perative. still much to be learned. Shorebird censuses ACKNOWLEDGMENTS are continuing under the Pacific Flyway We thank all of those who contributed information Project, and a year-long study of shorebird about the birds of the wetlands, and especially F. He- use of Bahia San Quintin will add data on redia and R. A. Mendoza. We are grateful also to C. seasonality in that important wintering and T. Collins, R. A. Mendoza and G. W. Page for critical reading of the manuscript. migratory ground. The use of mangroves by breeding and wintering Ciconiiformes and LITERATURE CITED wintering Passeriformes needs further doc- AMADOR, E. S. 1985. Avifauna de Isla Santa Mar- umentation, as does the importance of the garita, Baja California Sur, Mexico. Bachelors’ The- small, scattered freshwater marshes to birds sis, Universidad Autonoma de Baja California Sur, Mexico. 42 pp. restricted to such habitat, e.g., Beldings’ BANCROFT,G. J. 1927a. Breeding birds of Scammons Yellowthroat. Lagoon, Lower California. Condor 29:29-57. Conservation of natural habitat has be- BANCROF~,G. J. 1927b. Notes on the breeding coast- al and insular birds of central Lower California. Con- come an increasingly important issue under dor 29:188-195. the present Mexican government and co- BRYANT. W. E. 1889. A cataloaue ofthe birds ofLower operative programs between U.S. and Mex- California, Mexico. Proceedings of the California Academy of Sciences, Series 2, 21237-320. ican wildlife agencies are expanding. En- CASTELLANOS,V. A. 1982. Distribution, abundancia forcement of the law, creation of reserves, y productividad de1 Aguila Pescadora. Biologia 12: and protection of endangered species are in 11-16. COLLINS, C. T., W. A. SCHEW,AND E. BURKETT. 199 1. their infancy. For example, the vast Vis- Elegant Terns breeding in Orange County, Califor- caino Biosphere Reserve extends across the nia. American Birds 45:393-395. peninsula and includes lagunas San Ignacio CONANT, B., J. F. VOEUER, AND J. C. DIAZ 1990. Winter waterfowl survey Mexico west coast and Baja and Ojo de Liebre, but it is as yet a reserve California. U.S. Department ofthe Interior, Fish and in name only, there is neither headquarters Wildlife Service. Portland. OR. nor personnel to implement protection. CONANT B., J. F. VOELZER, A&D S. T. MORALES. 1992. Mexico winter waterfowl survey 1992. U.S. De- Tourist developments have impacted oartment of the Interior. Fish and Wildlife Service. some wetlands and there are new projects Portland, OR. in the planning stage. At Ester0 de Punta CONTRERAS, F. 1988. Las lagunas costeras Mexica- nas. Centro de Ecodesarrollo. Secretaria de Pesca. Banda a resort development has destroyed Mexico. 263 pp. two thirds of the barrier beach since 1987 DANEMANN,G. D.,ANDJ. R. Gu&Poo. 1992. Notes BAJA CALIFORNIA WETLANDS--Massey and Palacios 51
on the birds of San Ignacio Lagoon, Baja California PAGE, G. W., W. D. SHUFORD, J. KJELMER, AND L. E. Sur, Mexico. Western Birds 23: 1 l-l 9. STENZEL. 1992. Shorebird numbers in wetlands of ERICKSON, R. 1992. A recent Black Rail record for the Pacific flyway: a summary of counts from April Baia California. The Eunhonia 1: 19-2 1. 1988 to January 1992. A renort of Point Reves Bird EVE&T, W. T., AND D. W: ANDERSON. 199 1. Breed- Observatory, 4990 Shoreline Highway, Stinson ing seabirds of Baja California and the Gulf of Cal- Beach, CA 94970. ifornia. PD. 115-l 39 in J. Croxall (ed.). Seabird sta- PALACIOS,E., AND L. ALFARO. 199 1. Breeding birds tus and conservation: a supplernent.Intemational‘ of Laguna Figueroa and La Pinta Pond, Baja Cali- Council Bird Preservation Technical Publication No. fornia, Mexico. Western Birds 22:27-32. 11. PALACIOS,E., AND L. ALFARO. 1992a. First breeding GRINNELL, J. 1928. A distributional summation of records of the Caspian Tern in Baja California, the ornithology of Lower California. University of (Norte), Mexico. Western Birds 23:143-144. California Publications in Zoology 32: l-300. PALACIOS,E., AND L. ALFARO. 1992b. Occurrence of HENNY, C., AND D. W. ANDERSON. 1979. Osprey dis- Black Skimmers in Baja California. Western Birds tribution, abundance, and status in westem North 23:173-176. America: III. The Baia California and Gulf of Cal- PALACIOS,E., A. ESCOFET,AND D. H. LOYA-SALINAS. ifornia population. Bulletin Southern California 199 1. The Ester0 de Punta Banda, B.C., Mexico as Academy of Sciences 78:98-106. a link in the “Pacific Flyway”: abundance of shore- HOWELL, S. N. G., AND S. WEBB. 1992. Noteworthy birds. Ciencias Marinas 17: 109-l 3 1. bird observations from Baja California, Mexico, Oc- PALACIOS,E., AND E. MELLINK. 1992. Breeding bird tober 199 1. Western Birds 24:57-62. records from Montague Island, northern Gulf of Cal- HOWELL, S. N. G., AND S. WEBB. 1993. New and ifornia. Western Birds 23:41-44. noteworthy bird observations from Baja California, PALACIOS, E., AND E. MELLINK. 1993. Additional Mexico. Western Birds 23: 153-163. breeding bird records from Montague Island, north- HUEY, L. 1927. The bird life of San Ignacio and Pond em Gulf of California. Western Birds 24:259-262. lagoons on the western coast of Lower California. PITELKA, F. A. 195 1. Speciation and ecological dis- Condor 291239-243. tribution in American jays of the genus Aphelocoma. IBARRA-OBANDO,S. E. 1990. Lagunas costeras de Baja University of California Publications in Zoology California. Ciencia y Desarrollo 16:39-49. 50(3): 195-464. JEHL, J. R., JR. 1977. History and present status of ROBERTS, N. C. 1989. Baja California plant guide. Ospreys in northwestern Baja California. Transac- Natural History Publishing Company, La Jolla, CA. tions of the North American Osprey Research Con- SALINAS-ZAVALA, C. A., J. LLINAS, AND R. RODR~- ference, U.S. Department of Interior, National Park GUEZ-ESTRELLA. 199 1. Aspectos biologicos de1 Service Transactions and Proceedings Series, No. 2. Aguila Pescadora. Pp. 265-293 in A. Ortega and L. KENYON, K. W. 1947. Breeding populations of the Arriaga (eds.), La Reserva de la Biosfera El Vizcaino Osprey in Lower California. Condor 49: 152-l 57. en la Peninsula de Baja California. Publication No. KRAMER, G. W., AND R. MIGOYA. 1989. The Pacific 4, CIB de Baja California Sur, A.C. La Paz, Baja coast of Mexico. Pp. 507-528 in L. M. Smith, R. L. California Sur. Pederson, and R. M. Kaminski (eds.), Habitat man- SANDERS,G. B., AND D. C. SANDERS. 198 1. Waterfowl agement for migrating and wintering waterfowl in and their wintering grounds in Mexico, 1937-64. North America. Texas Tech University Press. U.S. Department of Interior, Fish and Wildlife Ser- MORRISON, R. I. G., R. K. Ross, AND S. TORRES M. vice Resource Publication 138. Superintendent of 1992. Aerial surveys of Nearctic shorebirds win- Documents, I 49.66:138. tering in Mexico: some preliminary results. Progress WILBUR, S. R. 1987. Birds of Baja California. Uni- Notes. Canadian Wildlife Service, Canadian Min- versity of California Press, Berkeley CA. istry of the Environment. ZEMBAL, R., AND B. W. MASSEY. 198 1. A census of NELSON, E. W. 192 1. Lower California and its natural the Light-footed Clapper Rail in California. Western resources. Memoirs of National Academy of Sci- Birds 12:87-89. ences 16: l-94.