Holes in Bradford Pear

I just noticed these holes in the big Bradford pear in my yard.

They're regularly spaced, about a quarter-inch apart, forming lines every five inches or so from about a foot above the ground as high as I could see-- and they are only on the southern half of the trunk, and on just one of the several trunks:

I was pretty sure a woodpecker was at work (an alternative would have been some sort of insect emerging from the holes), but the photo below of a burr oak at Hidden Springs State Park in Illinois persuade me to the former hypothesis. They were made by a sapsucker.

Sapsuckers eat sap which contains occasional insects. That, I think, explains the regularity of the holes.