Isn't this just an extension of the normal
feature of birds (variable among groups though obvious in parrots) called
cranial kinesis. This describes the ability of birds in which the upper mandible
can be moved up or down, independently of the cranium. This is achieved by
moving the quadrate bone forward and backward as a lever, thus pushing the
maxilla up and down, using the pterygoid bone as the link. The only difference
in snipe from eg. parrots, being that instead of the hinge being at the base of
the maxilla, it is near the tip, just proximal to the join of the extended
pterygoid to the maxilla. This means that they can open the tip of the beak
because the hinge is near the tip, rather than at the base, near the skull. Of
course the lower mandible is hinged separately.
It is hard for us, as mammals, to imagine this,
because we have a completely different structure with only one hinge for the
lower jaw only, and that is at the dentary/squamosal. We are unable to move the
upper mandible independently of the cranium.
Sunday, 2 November 2003 10:45
Subject: Re: [BIRDING-AUS] Snipe
I followed a
hunch on the name of that bill-bending feature and did an internet search.
It's called "rhynchokinesis", and is apparently present to a
greater or lesser extent in all(?) shorebirds, and some other birds. It is
particularly used by longer billed shorebirds. The following url points to a
brief abstract on a book on the exact subject, though it looks rather
technical to me.