Inventory and conservation of breeding waterbirds at Ojo de Liebre and Guerrero Negro Lagoons, Baja California Sur, Mexico

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 o ccurred since 1926 in the species composition of the community of breeding waterbirds, in the arrangement of their nesting substrate and in their popu lation size. Of 17 species breeding in the area in 1926, we found 12 nestin g there during our survey. Additional data from other researchers allowed u s 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 stil l considered to be a local breeder. Three species (Egretta alba, Larus atri cilla and Falco peregrinus) became new established breeders. Most of the sp ecies that breed on the islands within Scammon's Lagoon have a stable popul ation or have increased in number. None of the egret species breeding in 19 26 in marshes outside the islands currently nest there. Four species (Stern a antillarum, Charadrius wilsonia, Charadrius alexandrinus and Rallus longi rostris) breed on the islands or at other sites in the lagoons and vicinity . Despite development in the region, the natural wetlands and open-water co verage remain almost unchanged. Natural nesting substrates are mostly confi ned to the islands and are vulnerable to land predators, wave erosion and d irect human disturbance. These factors may have caused the shifting of nest ing spots from one island to another and to other suitable nesting sites on the lagoons, the urban landscape, the saltworks and man-made structures. B reeding waterbirds have been granted limited protection through reserves an d single-species conservation programs. We suggest guidelines to enhance th eir protection as a community in the context of El Vizcaino Biosphere Reser ve.