Woodpecker and sapsucker damage to trees: rows of holes, as extension services describe it

This page reports what the official source says. It is not legal advice: ask the office named here. Woodpeckers and sapsuckers are protected birds, and two of the sources below describe that protection: the University of California note names the Migratory Bird Treaty Act of 1918, and Iowa State University Extension says state and federal laws and an international wildlife pact protect them. The page describes what the sources say the damage looks like and the guards they list. It does not say what to do about any tree or bird. For protected species and nests in tree work, see the guide on wildlife and the law.

Two kinds of mark

The sources separate sapsuckers from the other woodpeckers. UC IPM (Pest Notes: Woodpeckers, publication 74124, revised April 2022) says gardeners may notice a series of small holes in rows pecked through the bark of a trunk or limb by a sapsucker seeking food, that the rows grow in number over time, and that the loss of sap may weaken the tree and give access to harmful insects or plant diseases. It adds that woodpeckers hunting insects can also strip bark off in scattered patches, giving a patchy look, and gives an oak trunk where the birds were feeding on larvae of the goldspotted oak borer.

Iowa State University Extension (Yard and Garden, yellow-bellied sapsucker entry) says that when holes in bark sit in uniform rows or columns the likely cause is a bird rather than an insect. It describes rows of holes about 1/4 inch across, usually between the branches, from a bird about 8 inches long that feeds mainly on the sap that runs out rather than on insects.

How big the holes are

The sources give different sizes. The University of Maryland Extension Home and Garden Information Center (updated December 13, 2023) puts sapsucker holes at 1/4 to 3/8 inch in closely spaced rows in healthy trees, and Iowa State at about 1/4 inch. Purdue University and the USDA Forest Service (FNR-216, hardwood plantations) say about 1/8 inch, evenly spaced in rings around the circumference of a limb or trunk. The sources do not explain the differences.

Which trees and when

Iowa State says sapsuckers attack many tree species but prefer pines, birches, maples and apple, and that in Iowa trees are damaged only when the birds pass through, from mid-September to mid-October on the way south and from late March to mid-May on the way north. It says that where the birds spend summer or winter they can feed heavily enough to kill trees, but that in Iowa the damage is noticeable and does not significantly weaken trees. Maryland says sapsuckers may feed on ornamental or fruit trees and that holes may enlarge through continued pecking or limb growth, with large patches of bark removed or sloughed off. Purdue says sapsuckers return to the same trees year after year.

Whether the sources call it harmful

Maryland says occasional girdling of a limb or trunk may kill a tree, and that on forest trees the feeding wounds can attract insects, porcupines and squirrels and can serve as entrances for disease and wood-decay organisms. Purdue says peck holes decrease timber value and can ruin a log for veneer if renewed every year, and may serve as entry sites for disease. Maryland also corrects one common idea: many woodpeckers make holes in sound wood where there are no insects, so holes are not always a sign of an insect problem. Related reading on borers that attract woodpeckers is in the guide to pests and diseases.

Guards the sources list

Maryland lists wrapping hardware cloth, plastic mesh or burlap around injured areas of valuable ornamental or shade trees, and says in orchards and forests it may be best to let sapsuckers work one or more of their favorite trees, since discouraging them may spread damage to more trees. Iowa State says protecting a large number of trees is usually not practical, that tree wrap or screening on individual trunks during the migration weeks might be useful, and that wraps should not stay on year-round because disease problems can increase. It says no insecticides or sprays control woodpeckers. The UC IPM note covers buildings more than trees; for houses it names netting as the most effective guard and says frightening devices and repellents more often fail than work.

The other animals in this group are listed on the wildlife damage to trees page.