How Is This Hairy Woodpecker Foraging?

A couple of weeks ago when it was warmer, a large group of wasps/hornets were converging on the side of Mr. Neil's house. There was more than one species and I'm not up on all of them, but it was kind of scary to watch. Leaf cutter bees and mason bees will sometimes use gaps in wood to lay eggs and woodpeckers love to find them and eat them.

This hairy woodpecker was working the roof area in search of food--despite the massive amounts of suet and mixed nuts I had filled in the feeders below. Hello?? I was trying to watch the hairy to see how she was foraging for the food. Was she randomly poking, looking or hearing the larvae?

The bird appeared to be putting the side of her head to the shingles and gaps, actively listening...or was she just looking? According to my beloved Bent, the birds are suspected of having excellent hearing. In his book, there is a quote from Minnesota's Dr. T.S. Roberts:

"The active grub, as it crunches the wood, makes a sound that would surely be audible to a bird with its keen sense of hearing. The tunnel produces a cavity which would give both a different sound and feeling on tapping over it. Such things as grubs have a strong odor, and it is probable that this plays a part also."

I checked BNA to see what modern thinking is and couldn't find anything that supported hairy woodpeckers having a great sense of hearing but did discuss using percussion for locating prey:

"Percussion not a means of securing prey, but rather a means of locating prey by rapidly tapping along a branch or trunk, presumably in order to hear resonance produced when tapping is above tunnel of a wood-boring insect."

So, that would add to why the woodpeckers are pecking, not just boring to get to the food, but testing for sounds of food. Interesting.