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A breeding eagle owl perches next to a rock is has marked with its white feces. Photo Courtesy of Vincenzo Penteriani
In what’s likely an effort to mark their territory, eagle owls have come up with their own “No Trespassing” signage: squirting feces and piling feathers in strategic places near their nests. Researchers Vincenzo Penteriani and Maria del Mar Delgado of Spain’s Estación Biológica de Doñana monitored 20 sites inhabited by the large European bird during its pre-egg laying and nesting stages. They found that in areas close to home, breeding owls preferentially “paint” large, dark rock faces and other prominent structures with their white feces. They also choose similar sites to pile feathers plucked from prey with bright, visible plumage, such as azure-winged magpies and little egrets. In past studies the scientists showed that eagle owls—which are known for their aggressiveness—also communicate vocally to warn off intruders. But poop and feather piles are a more enduring signal. “They leave a message [that says], ‘I’m not here, but this is my territory,’ ” says Penteriani. “It’s like private property.” (For more photos of eagle owls and their creations, click .)—Julie Leibach, from magazine