Â鶹´«Ã½

IT IS obvious to us that objects moved by a gentle wind must be light, and those not moved are heavy, but can animals work this out? It seems some crows can.

Sarah Jelbert at the University of Cambridge and her colleagues investigated by training 12 New Caledonian crows to discriminate between light and heavy objects. Six birds were rewarded when they dropped light objects into a food dispenser, and six were rewarded for choosing heavy objects. During this training, the birds were able to touch and pick up the objects.

Then pairs of unfamiliar objects, one light and one…