New pressure sensory feeding mechanism in birds

Miscellaneous: New pressure sensory feeding mechanism in birds

A wader bird, the knot, was observed to have special feeding habits. With its bill it probes the muddy edge of tidal flats at a fixed spot at a frequency of about 10 Hz, over a little less than a second and to a depth of about 1 cm. After that, it changes its bill angle and with one deep (>2 cm) probe in a different direction it retrieves any hard object sitting there. This can be its hard-shelled prey, or even a stone. The latter excludes its detection mechanism to rely on its prey producing chemicals (smell) or sound. The presence of many sensory corpuscles on the bill (as observed under the microscope) suggest the mechanism involves a pressure sensing mechanism. The time scales suggest the knot utilizes the peculiarities of the muddy sand: its rapid initial probing pumps up the pressure in the vicinity of the bill, which is then released by draining through the rigid sand-grain network. This is obstructed however by the rigid body, further away, which perturbs the pressure field, to the extent that this is apparently felt at the tip of the knot's bill.

Publications:
Piersma, T., Aelst, R. van, Kurk, K., Berkhoudt H., Maas, L.R.M. (1998) A new pressure sensory mechanism for prey detection in birds: the use of principles of seabed mechanics? Proc. R. Soc. Lond. B, 265: 1377-1383.