The mainland west coast of Mexico (Region 27*) contains several important areas for waterfowl. These habitats consist of tidal estuaries connected with brackish water marshes along the coast and inland fresh water wetlands and reservoirs. Fresh water streams and irrigation water empty into tidal lagoons and create flats, tidal pools, mangrove swamps and emergent vegetation dominated by cattail, bulrush, wigeongrass, muskgrass and algae.
The coastal and interior wetlands in the state of Sinaloa support 22.5% of the migratory waterfowl that winter in Mexico. The states of Sonora and Nayarit held 6.1% and 4.5%, respectively. These wetlands and their wildlife are currently threatened by intensive agriculture, pollution, and development by the shrimp industry along the 2,124 km of littoral habitat that exists in the three states. Sonora encompasses 1,200 km with 66,000 ha of wetlands; Sinaloa 656 km with 453,200 ha of wetlands, and; Nayarit has more than 268 km where Marismas Nacionales encompass 200,000 ha.
Adjacent to the west coast lies 1.2 million ha of irrigated agriculture in the state of Sinaloa (including Los Mochis, Guasave, Guamuchil and the Culiacan agricultural valleys) and approximately 456,000 ha in the state of Sonora (including the Yaqui and Mayo valleys). These upland areas were converted to intensive agriculture during the last 30 to 40 years. As a result there have been major changes to west coast wetlands, as they have become less saline, more densely covered by cattails, and subjected to discharges of agricultural pesticides and fertilizers.
During the last decade, the shrimp industry has grown rapidly and caused important changes in the wetland areas of the three states. In Sinaloa for example, 227 shrimp farms have modified 21,357 ha of intertidal and mangrove swamps. There is only limited regulatory control by the state and federal governments. An additional 200,000 ha are targeted for more of this development (Dir. Pesca, Gob. del Estado de Sinaloa 1999). Thus we are concerned that there will be further deterioration those wetlands. We have observed considerable habitat loss following the construction of 11,000 ha of shrimp farms in the Chiricahueto area and on Pabellon Bay. The shrimp farm industry has not grown as much in Sonora (5,252 ha) and Nayarit (1,217 ha) but the potential for this to happen is enormous (Carrera and de la Fuente 1995). The shrimp industry and agriculture are the most significant threats these areas will face in the near future. Growth of the shrimp industry is supported by a loan from the World Bank.
Much of the irrigated farmland supported rice production after it was developed. This crop is very beneficial to waterfowl. However, between 1981 and 1998, rice production has decreased in the state of Sinaloa from 65,900 to 2,400 ha. This was correlated with a drop in use of the region by northern pintail from 880,000 birds in 1989, to 228,000 in 1990 and 310,000 for 1991. About 5,000 ha of 21.2 million ha of agricultural land on the west coast is currently in rice production. These changes are due to production costs in comparison to other crops.
Importance to waterfowl
The complex of coastal wetlands along the states of Sonora, Sinaloa and Nayarit, represent the most important habitats for waterfowl in Mexico. Key wetlands in this area account for 33.1% of the total waterfowl population that winters in Mexico (USFWS 1989). On these wetlands during the 1980s, El Tobari Bay normally held, 1.8%, Lobos Bay, 0.3%, Santa Barbara, 1.6%. Agiabampo, 2.4%, Topolobampo Bay, 7.3%, Santa Maria Bay, 1.7%, Pabellon Bay, 9.4%, Caimanero, 1.9%, el Dorado to Dimas, 2.2% and Marismas Nacionales, 4.5% of the wintering waterfowl in Mexico (USFWS 1989). In January 1997, the USFWS reported a total of 627,787 ducks and 24,797 Geese, distributed along the western mainland. Of the ducks reported, 556,390 were dabblers and 71,397 were divers. Of the dabblers, the northern shoveler accounted for 251,950 (45%), the pintail, 151,740 (27%), blue-winged and cinnamon teal, 45,375 (8%), green-winged teal, 45,695 (8%) and American wigeon, 43,825. Of the divers, scaups accounted for 43,430 (64%), redhead, 17,900 (26%), ruddy duck 3,950 (6%) and canvasback, 2,050 (3%). Of the geese reported black brant accounted for, 22,720 (92%), snow geese 1,405 (6%) and white-fronted goose, 662 (3%).
*Region 27 - NABCI Bird Conservation Region 33 Sonoran and Mohave Deserts