Spiders that spin orbed webs run the risk that low-flying birds will take out their hard-built structures. This may explain why some spiders weave conspicuous patterns into the centers of their webs - patterns whose function has puzzled biologists.Skip to next paragraph
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Thomas Eisner and Stephen Nowicki of Cornell University say they have demonstrated this notion experimentally. They report in Science that birds do indeed veer off to avoid well-marked webs while flying through other webs. They note that the markings, clearly visible to humans, probably also help larger animals avoid sticky entanglement.