Isla Partida
Granitic Isla Partida, about 2 square miles in size, lies just south of Angel de la Guardia. Because of its lack of vegetation , bats are the only resident mammals. At sundown ,this desolate island comes alive with the sounds of thousands of Fishing Bats (Pizonyx vivesi)which crawl from their subterranean refuges and take flight together in search of food. They swoop down over the water of the Gulf gathering small fish and crustaceans. During the day, these bats are found beneath rock crevices on the talus slopes of Partida. The are not found elsewhere in the world.
Isla Raza
Just south of Partida, Raza, at .75 square miles, barely stands above the height of the water. In February and March, hundreds of thousands of Herman's Gulls begin a pilgrimage to Raza from throughout the Pacific. Once here, they scratch out nests in the guano and on the beaches to set up housekeeping. In April, thousands of Elegant Terns arrive and attack the nesting gulls at night, eventually usurping part of their nesting grounds and eating the gull eggs.
Having already bred, the Terns lay eggs and concentrate on defending the beachhead they've established -- 95% of the world's population of the Elegant Terns nest here. Throughout the day, gulls counterattack by diving and pushing the smaller Terns aside to eat their eggs in turn. This warfare continues day after day throughout the summer, but since there are many more gulls than Terns, it is very difficult for the Terns to maintain their nesting areas. Despite these daily mutual hostilities, hundreds of thousands of eggs are produced, and both the gulls and Terns are able to perpetuate their species.
Cruise the Sonoran Desert by Boat
