Woodpecker Holes in Oak Trees: Sapsucker Damage and Carpenter Ants

I've heard woodpeckers working on my four mature oaks and discovered rows of holes. Carpenter ants are also present. Should I fill these holes, and if so, with what material? I'm worried about losing my trees.

Identifying the Culprit: Yellow-Bellied Sapsuckers

The evenly spaced horizontal or vertical holes indicate yellow-bellied sapsuckers, not typical woodpeckers. These birds feed on tree sap (over half their diet) along with insects attracted to the sap. They create holes, sap flows, insects gather, and the sapsuckers return to eat the insects.

Impact on Oak Trees

Oaks have thick bark, so damage is minimal. Thin-barked trees like maples suffer more. Rarely does sapsucker feeding kill a tree, though it may weaken it, inviting secondary pests and diseases.

Management Recommendations

Do not fill the holes. The tree will naturally compartmentalize and heal them. To discourage sapsuckers, spray the affected area with an insecticide like malathion or carbaryl (Sevin) to eliminate the insects attracting the birds. Alternatively, doing nothing is acceptable since tree health isn't significantly threatened.