Dear Birders,
While looking at bar tailed godwits at Penhryn Estuary (Botany Bay, Sydney)
recently I noticed again the way in which the upper mandible of some waders
curls upwardly as the bird opens its beak. I imagine that this is an
evolutionary adaptation to probing for polychaete and other worms in sand or
mud. If the tip of the beak opens more than the rest of the beak then the
amount of sand or mud required to be displaced to grasp a food item is
decreased.
A neat adaptation, but it set my mind working. How does the bird do this? Is
the amount of curl of the bill tip controllable by the bird or is it fixed
relative to the amount of opening of the bill? Has this adaptation arisen only
once in waders and been inherited or has it evolved separately in different
groups?
Regards
Peter Marsh
Birchgrove NSW
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