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Walnut trees shade the streets of Davis, California. They also provide food for the crows that roost near Davis. Crows crack walnuts by dropping them from heights of 5–10 meters or more onto sidewalks, roads, and parking lots. Occasionally they drop walnuts in front of approaching cars, as if using the cars to crush the nuts for them. Do crows intentionally use cars as nutcrackers? Some of the citizens of Davis, as well as some professional biologists (Maple 1974, in Cristol et al. 1997) were convinced that they do, at least until a team of young biologists at UC Davis put this anecdote to the test (Cristol. | COGNITION EVOLUTION AND BEHAVIOR SECOND EDITION Cognition Evolution and Behavior This page intentionally left .
