A Very Busy Bird

We parked near the same tree that hosted the Red-breasted Sapsucker on Monday - see previous post.  He wasn't there, so we inspected the tree.  Boy, was he busy!  And probably took a geometry course.  Very systematic work.  I haven't studied birds much, so I aim to find out - by observation and/or reading - whether the bird is eating sap and just mining sap to catch insects.  There were a number of small flies and ants either consuming sap or becoming trapped in it.  The tree seemed no worse for the wear, and the sap tasted pretty sweet.