Need to document Rhynchokinesis in long-billed shorebirds

Dato’ Dr Amar-Singh HSS’s earlier post on the Common Snipe (Gallinago gallinago) with a video clip showing the bird preening an feeding in shallow water HERE attracted the attention or another birder who pointed out to him the phenomenon of rhynchokinesis. This in turn led Amar posting another account, illustrated with images of the phenomenon HERE.

For the sake of readers unfamiliar with the word, rhynchokinesis is the ability to open the tip of a long bill, so as to be able to feed in mud, silt or soil (Erritzoe et al., 2007). This bill adaptation, seen in many long-billed shorebirds (Scolopacidae), is associated with deep rhythmic probing into the soft ground without the need to remove the bill from the soil. Also, the force needed to open the bill in the substratum to catch the food items is much reduced.

Other examples include Bar-tailed Godwit (Limosa lapponica), with capability of upward and downward flexing; and Terek Sandpiper (Xenus cinereus) and Swinhoe’s Snipe (Gallinago megala), both capable of flexing their upper mandible upwards LINK. There are also species in other groups exhibiting rhynchokinesis as well.

Inspired by Amar’s post on rhynchokinesis in the Common Snipe, birder-photographer Chan Yoke Meng sent in images of a Pintail Snipe (Gallinago stenura) exhibiting the phenomenon. Note that the bending zone is about a third from the tip of the bill. In most other birds the upper mandible moves upward at the junction with the skull, or even further out, known as prokinesis (Erritzoe et al., 2007).

Now that this phenomenon has been publicised to the local birdwatching community, we suggest that next time photographers and videographers are out in the field, keep an eye on such bill adaptation, especially in birds with long bills.

YC Wee, Chan Yoke Meng & Melinda Chan
Singapore
April 2014

References:
1. Erritzoe, J., K. Kampp, K. Winker & C. B. Frith, 2007. The ornithologist’s dictionary. Lynx Edicions, Barcelona. 290 pp.
2. Estrella, S. M. & J. A. Masero, 2007. The use of distal rhynchokinesis by birds feeding in water. The Journal of Experimental Biology 210, 3757-3762.