Charlie MV is on the money, birds could care less if they roll in pepper. I didn't know that some store bought suets contained pepper to deter squirrels. Neat! We make our own suet over here and that's a handy little fact to have in my back pocket as I never thought of trying to toss in pepper to my suet mix. Thanks so much for mentioning that Charlie MV.
There is a reason why this bird's common name contains the word sapsucker. I suspect the bird is having a go at all of your trees to get to the sap.
I've never seen sapsuckers do any long term harm because trees will callous over the small wounds made by the bird. One thing though, it's been my experience sapsuckers generally choose trees that are already stressed or diseased so you might want to check into if anything else is going on with your trees.
excerpt from above-
Like any good forester, sapsuckers are selective in using particular trees over others, and they invest a lot of time in managing trees for both current and future use. They are known to feed on as many as 1,000 different species of trees, although they show a preference for certain species within a given area. Birches, sugar maples, and scotch pines are a few common favorites. They often will select individual trees that are wounded or weakened, such as from insects, disease, lightning, or wind. The reason for this may be because the sap of trees in poor health contains higher levels of amino acids and protein.
Way cool that you have of these birds on your property starlite626!