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March-April 2011

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Mexico's Midriff Islands—Wealth of Life in the Heart of a Scorching Desert

Composed of more than 50 islands ranging in size from tiny rocas (boulder-sized points of land that barely jut above the sea's surface) to Mexico's largest island, Isla Tiburón (450 square miles), the sparsely vegetated Midriff Islands rise into the desert skies above and in stark contrast to the soothing turquoise waters of the Gulf of California. True desert islands though they may be, they and the waters (and skies) around them are anything but deserted. Created when plate tectonic action tore what is today the Baja California Peninsula away from modern mainland Mexico along the San Andreas fault zone, the Midriff Islands stand as remnants in this tremendous geologic rift (a separation that continues to this day). Both the coastline of the mainland and that of the Baja California peninsula arc in toward one another, hence the moniker “midriff.”

Due to a number of factors, including deep, cold water mixing with shallow, warm sun-blasted water as strong tides churn through the Midriff Islands, tremendous amounts of aquatic life thrive in this area. And because most of the smaller islands of this archipelago have no endemic mammals (hence predators) living on them, they are the perfect places for migratory birds to stop and breed. Different species have used specific islands in the Midriff year after year to nest and procreate, including pelicans, gulls, and terns. Isla Rasa (rasa means flat in Spanish) hosts hundreds of thousands of elegant and royal terns each spring, along with some Heermann's gulls. A spring journey to Isla Rasa grants one of the most extraordinary experiences in the natural world—the almost deafening collective noise from hundreds of thousands birds nesting and streaking through the air. The birds collect food from the sea, then bring it back to nests that lie atop this tiny patch of desert land amid a turquoise sea, in the dry, Sonoran desert air.

ED DARACK is an independent writer and photographer. Visit his Web site at

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