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“In 19951995, (scientist) Theunis Piersma showed that Red Knots find shellfish up to eight times more frequently than would be expected if they were doing random searches...As a knot's bill descends into the sand, it pushes on the thin rivulets of water between the rains, creating a pressure wave that radiates outward. If there's a hard object in the way - say, a clam or a rock - the water must flow around it, which distorts the pattern of pressure. The pits on the knot's bill tip can sense those distortions, detectings surrounding objects without having to make contact with them. This ability, which Piersma calls "remote touch" is impressive enough, but the knot improves it even further by probing the same areas repeatedly, stabbing its beak up and down several times a second. This stirs up the sand grains, which settle into a denser configuration, heightening the buildup of pressure from the beak and making the distortions more obvious. Every time the knot lowers its head, the foud around it becomes more obvious, as if it were using a kind of sonar based on touch instead of hearing.” — Ed Yong