A quirk in a bird's hunting behavior has given scientists a rare chance to measure an evolutionary force in action in the wild.
When a loggerhead shrike catches a lizard, the bird often impales it on a thorn or a spur of barbed wire and then leaves the carcass hanging, explains evolutionary biologist Edmund D. Brodie III of Indiana University in Bloomington. He and his colleagues compared the length of the horns on dangling remains of horned lizards with horn lengths of lizards still alive. The living lizards typically had slightly longer horns, the researchers report in the April 2 Science.
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