Abstract
Surveys made in 1997/98 at the lagoons of Ojo de Liebre (Scammon´ s Lagoon) and Guerrero Negro, Baja California Sur, Mexico, showed that changes have occurred since 1926 in the species composition of the community of breeding waterbirds, in the arrangement of their nesting substrate and in their population size. Of 17 species breeding in the area in 1926, we found 12 nesting there during our survey. Additional data from other researchers allowed us to conclude that 16 species have nested in the area after 1984. Only one species (Sterna elegans) has not been reported nesting; however, it is still considered to be a local breeder. Three species (Egretta alba, Larus atricilla and Falco peregrinus) became new established breeders. Most of the species that breed on the islands within Scammon´ s Lagoon have a stable population or have increased in number. None of the egret species breeding in 1926 in marshes outside the islands currently nest there. Four species (Sterna antillarum, Charadrius wilsonia, Charadrius alexandrinus and Rallus longirostris) breed on the islands or at other sites in the lagoons and vicinity. Despite development in the region, the natural wetlands and open-water coverage remain almost unchanged. Natural nesting substrates are mostly confined to the islands and are vulnerable to land predators, wave erosion and direct human disturbance. These factors may have caused the shifting of nesting spots from one island to another and to other suitable nesting sites on the lagoons, the urban landscape, the saltworks and man-made structures. Breeding waterbirds have been granted limited protection through reserves and single-species conservation programs. We suggest guidelines to enhance their protection as a community in the context of El Vizcaíno Biosphere Reserve.
Highlights
INTRODUCCIÓNScammon’s (Ojo de Liebre) and Guerrero Negro lagoons comprise one of the few relatively well-preserved wetlands on the west coast of Mexico (Wilson and Ryan, 1996)
Because of the variety of habitats, species richness and size of the populations of migratory and resident waterbirds found in this area, the Mexican government recognized it as one of priority for conservation, establishing a wildlife refuge in 1972 and including both lagoons in the El Vizcaíno Biosphere Reserve in 1988 (Breceda et al, 1995)
Estas lagunas integran una zona importante de reproducción para muchas especies de aves acuáticas en la costa occidental de la península de Baja California
Summary
Scammon’s (Ojo de Liebre) and Guerrero Negro lagoons comprise one of the few relatively well-preserved wetlands on the west coast of Mexico (Wilson and Ryan, 1996). Carmona and Danemann (1998), and Danemann and Carmona (2000) documented spatiotemporal distribution patterns of the waterbirds at the Guerrero Negro saltworks, an area not included in our study Despite these studies, there is a lack of current and detailed information on the breeding waterbirds in the lagoons, because after the pioneering work of Bancroft (1927), no other focused, comprehensive survey has been made. Distribución de las principales colonias reproductoras de aves acuáticas en la Laguna Ojo de Liebre, Baja California Sur, México structures located inland suitable as nesting sites for raptors). Governmental protection programs implemented in the region were analyzed to clarify their role in the conservation of breeding waterbirds
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