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.