Wide open now!
Sounds like a good new Bob Dylan track title!
The bill of the Puffin is pretty obvious and unique. The gape is those yellow blobs at the base of the bill as you see in the first picture. The tongue holds the sand eels down in the bill, it goes up into the roof of the mouth and holds down the sand eels, the advantages of this are displayed.
The warden on Inner Farne told us the record apparently is 67 sand eels in one bill (not a lot of people know that), I have no idea how that is known . Perhaps it should be in the Guinness Book of Records as it sounds out of this world!