Ildefonso is a small, rugged island that is home to many nesting seabirds, including blue-footed and brown boobies. Isla San Ildefonso -- home to a number of nesting seabirds, including ospreys and brown- and blue-footed boobies. Some of the best tidal pools in the Sea of Cortez line the shore, along which crustaceans, starfish, anemones, and a wide array of fish can be seen.