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Isla Garza and Isla Pelicano in Laguna San Ignacio, Baja California Sur, Mexico historically served as roosting and nesting sites for numerous marine bird species that made their nests either in the Islands’ sparse, low vegetation or directly on the ground. At times, these colonies of ground-nesting birds contained as many as several thousand individuals. Inspection of the Islands’ avian rookeries in February and March 2010 revealed complete reproductive failure of all ground-nesting birds and evidence of coyote intrusion and predation at many nest sites. The authors strongly suspect that the islands no longer provide secure reproductive habitat for these avian populations, and that predation by coyotes in recent years may be a primary cause of this decline.
The collapse of the Islands breeding populations represents a significant loss of breeding habitat and resources for all of the avian species that reside in the Laguna San Ignacio and Baja California Sur region. Mitigation measures and protection from predation should be considered to restore the quality of the breeding habitat for the birds and to encourage re-colonization of these unique areas. Management actions directed at restoring the integrity of the islands as an avian breeding habitat need to be undertaken in harmony with the goals, objectives, and regulations of the Vizcaino Biosphere Reserve which the lagoon and its islands are a part, and should reflect the needs and requirements of all the involved species, predator and prey alike, as well as the ecological balance of the Laguna San Ignacio ecosystem. Thus, any predation management program needs to consider management actions taken elsewhere in comparable situations that have been successful in addressing similar issues.
They recommend that a group of experts convene to: (1) evaluate the specific conditions on Isla Garza and Isla Pelicano fundamental to this recent decline; (2) identify and evaluate management actions that would mitigate predation and restore the avian nesting and roosting habitat over the long-term; and (3), establish a monitoring program to evaluate the success of any management actions undertaken.