STATUS, DENSITY AND HABITAT RELATIONSHIPS OF THE ENDEMIC TERRESTRIAL BIRDS OF SOCORRO ISLAND, REVILLAGIGEDO ISLANDS, MEXICO

Socorro Island supports the highest plant and animal diversity of the Revillagigedo Islands. Eight endemic terrestrial bird species (one end emic genus and seven endemic sub-species) 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 a nd density of the endemic avifauna and on the degree of habitat distur bance on Socorro Island. We found that plant species richness, plant d ensity, 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 in cluding sheep over-grazing, erosion, predation by feral cats, and huma n disturbance. Therefore, we propose that the island be protected by m eans of an integratedresource management plan and be designated as a l egally protected area. Five management strategies are needed immediate ly. Finally, we propose to work jointly with Mexico military personnel to manage, improve, and preserve the ecosystems of Socorro Island. Co pyright (C) 1996 Elsevier Science Limited.