Food Webs and Feeding Habits on the Revillagigedo Islands, Mexico

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Abstract: Food webs on oceanic islands are often markedly different from continental food webs due to low species diversity and absence of key components of mainland ecosystems. Food webs and feeding habits are described from observations and scat, pellet, and gut analysis on the four islands of the Revillagigedo Islands, Mexico, when in their near-original state. Changes in food habits after introduction of exotics are described. Food webs increase in complexity with increase in island size, largely as a function of increase in habitat diversity seen with an increase in island size. Seabirds are the major components of food webs on the two smaller islands, and reptiles, passerine birds, hawks, owls, parrots, and doves are more important on the two larger islands. Some island vertebrates have food habits similar to those of their mainland counterparts, but others have become food specialists (e.g., the Socorro Red-tailed Hawk, in the absence of small mammals, eats mostly lizards and land crabs). Other bir...