They could also be due to a large insect which will work itself free and fall out The spider knows if the insect caught in the web is small its struggling legs will create the just right kind of vibrations and the spider will dash out and immobilise the prey with a single, poisonous bite. Many members of the bird world too rely on sense of touch to find food. For instance, debbling ducks and probing plovers use touch to find prey. The number of touch receptors or corpuscles in the end of the bill of these birds exceeds even the nerve endings in the human finger-tip. Using this sense, most waders can blindly explore sand and mud, and avocets are able to sweep ahead of them, snapping up any tiny aquatic creature it might touch.
Spoonbills work with curious-shaped bills in the same way.
Woodpeckers have touch-sensitive cells at the tip of the tongue. With these, they can explore the tunnels of wood-boring insects and insect larvae. Once located, the juicy morsel is hooked out by the bird s barbed and sticky tongue. The most extraordinary reliance on touch is, perhaps, shown by the skimmer. Seen head-on, it is very thin and is built to offer minimum resistance.