Rhynchokinesis

Rhynchokinesis is an ability possessed by some birds to flex their upper mandible. Rhynchokinesis is one of two types of cranial kinesis, the other being prokinesis, in which the upper mandible moves at the point where it is hinged with the bird's skull. Rhynchokinesis on the other hand involves flexing at a point some way along the mandible - either upwards, in which case the upper and lower mandibles diverge, resembling a yawn, or downwards, in which case the tips of the mandibles remain together while a gap opens up between them at their midpoint.

Unlike prokinesis, which is widespread in birds, rhynchokinesis is only known in cranes, shorebirds, swifts and hummingbirds.

Species in which this has been recorded photographically include the following species: Short-billed Dowitcher, Marbled Godwit, Least Sandpiper, Common Snipe, Long-billed Curlew, Pectoral Sandpiper, Semipalmated Sandpiper, Eurasian Oystercatcher and Bar-tailed Godwit (see Chandler 2002 and external links).

External links

Photographs of birds performing rhynchokinesis can be found here:
* [http://birdcentral.net/SBdowitcher1B.jpg] - a Short-billed Dowitcher
* [http://www.photos-of-the-year.com/image/nature/632/3593open_beak_godwit-med.jpg] - a Marbled Godwit
* [http://www.birdforum.net/attachment.php?s=30bab082f6b003975d2f1fcf23344ee1&attachmentid=10972] - a Least Sandpiper

References

* "A functional and evolutionary analysis of rhynchokinesis in birds" by Richard L Zusi, Smithsonian Institution Press, 1984.
* Chandler, Richard (2002) PhotoSpot - Rhynchokinesis in waders "British Birds" Vol 95 p395