Status, density and habitat relationships of the endemic terrestrial birds of Socorro Island, Revillagigedo Islands, Mexico Original Research Article

Socorro Island supports the highest plant and animal diversity of the Revillagigedo Islands. Eight endemic terrestrial bird species (one endemic genus and seven endemic subspecies) currently are present on the island. One endemic species is now extinct and the status of another endemic subspecies is uncertain. Forty visiting species (both seasonal and accidental) represent the non-endemic terrestrial avifauna of the island. In this work, we present quantitative data on the abundance and density of the endemic avifauna and on the degree of habitat disturbance on Socorro Island. We found that plant species richness, plant density, and number of vegetative strata in the less disturbed areas to be positively related to bird density. The simple community structure and fragile island ecosystem are now threatened by several factors including sheep overgrazing, erosion, predation by feral cats, and human disturbance. Therefore, we propose that the island be protected by means of an integratedresource management plan and be designated as a legally protected area. Five management strategies are needed immediately. Finally, we propose to work jointly with Mexican military personnel to manage, improve, and preserve the ecosystems of Socorro Island.