Q: A couple of my mature trees have developed holes in their bark over the years. Interestingly, they’re in a fairly even pattern, running up and down or horizontally across the trunk. Do you know what’s causing it and should I take any action?
A: This sounds like damage from a woodpecker, the Yellow-bellied Sapsucker. The evenness of their drilling pattern is characteristic of this species. They spend the winter in Maryland but breed further north in the summer (and in westernmost MD). Although a tree might eventually succumb to heavy damage, often their pecking causes no serious dieback.
They create small circular pits or larger rectangular patch “wells” in the bark to access the sugary sap flow. Insects attracted to the oozing sap are also eaten. They favor forest-edge habitat, plentiful in suburbia, where there tend to be faster-growing young trees. Hundreds of tree and shrub species can be used, but birds prefer those with high sugar content in the sap or those that are ailing or already wounded from prior pest, disease, lightning, or storm damage (and possibly excessive pruning).
You may be surprised to learn who else takes advantage of sapsucker activity. Northbound migrants of Ruby-throated Hummingbirds depend on these sap wells as an early source of nourishment before spring blooms are available. Porcupines (Western MD) and bats also utilize them, plus squirrels and several other bird species. Their chiseling, while perhaps inconvenient to us, is therefore invaluable to forest biodiversity. You can learn more about sapsuckers in Cornell’s All About Birds web database.
If you don’t appreciate their drilling on your garden plants, well…there’s little you can do. As a migratory, nongame bird, they’re protected from harm by the Federal Migratory Bird Treaty Act. You could exclude them by caging tree trunks that are being targeted, but this will simply force the birds to choose additional hosts in the area. Plus, it would be difficult to mount and secure such a barrier around a section of trunk with multiple branches. Don’t treat the trunk wounds with any sort of sealant, as that may hinder any healing that does occur. If any branches die back, just trim them off.
Have a plant or insect question? The University of Maryland Extension has answers! Send your questions and photos to Ask Extension.