Over the last few weeks I have watched and photographed Marbled Godwits
working the sandy edge of Quimper Bay / Port Townsend, probing with
their long recurved bills, plunging into the wet sand at water's edge.
What I am curious about, having seen them come up with food fairly
frequently.

My question is: how do these feeders sense that they have located
something edible? I thought that it could be touch, feeling a different
density of an object, or perhaps even taste or smell.

Those Godwits were quick about their repeated probing plunges, jamming
those bills several inches into the sand just as the receding water kept
the spot wettest. Quimper Bay is usually very calm water: the edge where
I was watching had just little ripples reaching shore. Time was on
rising tide, about 3/4 in.

I asked the Near Universe, Dr Google, but found nothing about it.
Anybody out there that can educate me?