What the holes are actually telling you
Woodpeckers don't go after healthy, solid wood. They go after insects. When a bird hammers repeatedly on the same tree, it has found something to eat inside that trunk. Michigan State University Extension is direct about this: concentrated woodpecker feeding on one tree is strong evidence of an insect problem in that tree, even when you can't see the insects yourself.
The size and shape of the holes matter a lot. Small, neat rows of holes, usually arranged in horizontal bands, are the work of sapsuckers, which drill for sap rather than insects. That's a different situation. Large, rough, rectangular cavities are pileated woodpecker work. Natural Resources Canada notes that pileated woodpeckers do not excavate in healthy, sound wood. Their presence means the wood is already soft, weak, or decaying.
Warning signs that make this more serious
Any one of these alongside heavy woodpecker activity deserves a closer look:
- Large, rectangular holes rather than small round ones
- Multiple holes spread across the trunk or major limbs, not just one spot
- Frass, fine, sawdust-like material, around hole openings
- Canopy thinning or dead branches at the top of the tree
- Bark splits or S-shaped galleries visible under loose bark
- Mushrooms or shelf-like conks growing at the base or on the trunk
That last combination, heavy woodpecker activity plus fungal growth at the root flare, is a red flag. Arborist guides flag this pairing as a sign that decay may be breaking down the core wood, not just the surface.
For ash trees in particular, watch for these signs together. Increased woodpecker feeding on the trunk is one of the early field signs of emerald ash borer infestation, often showing up before the canopy looks obviously sick.
What is probably not a crisis
Moderate woodpecker activity on an otherwise vigorous tree is not automatically a death sentence. Bartlett Tree Experts point out that the holes themselves rarely kill a tree, the birds are after insects, not wood. A few sapsucker rows on a tree that has a full, healthy canopy and no other symptoms is worth monitoring, not panicking over.
The distinction is volume, pattern, and location. One spot of activity is different from a trunk covered in holes. Holes near the base are more structurally worrying than holes high in the canopy.
When to act fast
Don't wait if the tree is near your house, a driveway, or anywhere people spend time outside. Internal decay is invisible from the ground. A tree can look passable until it fails. If you're seeing large cavities, frass, bark splits, canopy dieback, or fungal growth in addition to the woodpecker holes, treat that as urgent.
Start with the TreeNerd free tree-check tool for a quick read on your situation. For anything that raises concern, book a certified arborist for an on-site assessment. An ISA-certified arborist can probe the wood, check for hollow sections, and tell you what you're actually dealing with. No photo or checklist can do that, the only reliable answer comes from someone standing in front of the tree.