Sapsucker holes and the wasps that follow them
Why a sapsucker drills rows of small holes in bark, the wasps and hummingbirds that drink from them, when the damage matters, and how to guard a small tree.
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Sapsucker, borer or woodpecker?What the bird is doingWho else feeds at the holesDoes it hurt the tree?What not to do, and the little you can doCommon questionsSourcesSomeone finds the trunk of a maple or a holly ringed with small holes, dozens of them, as straight as if they had been drilled with a jig. Sap weeps from the holes and wasps crawl on them. The first guess is usually borers, and the first worry is that the tree is dying. Almost always the culprit is a bird, the yellow-bellied sapsucker, and the tree is in no real danger.
Sapsucker, borer or woodpecker?
Three kinds of holes get confused, and they mean different things.
| Sign | Sapsucker | Borer | Woodpecker excavation |
|---|---|---|---|
| Shape | Small, uniform and shallow, about a quarter inch across | Round or D-shaped, depending on the insect | Large and ragged, or a deep rectangular trench |
| Arrangement | Tidy rows and columns, often banded around the stem | Scattered at random, because they are exit holes made by adults leaving the tree | Irregular, not aligned in rows |
| Sawdust or frass | None, and fresh holes weep sap | Often sawdust-like frass or dried sap at the opening, or frass in bark crevices and at the base | Chips on the ground |
| Live or dead wood | Live bark | Usually a tree that was already stressed | Dead or dying wood, where the bird is after carpenter ants or beetle larvae |
| What to do | Nothing on an established tree; screen a small one while the bird is active | Get the tree looked at | Deal with the dead wood, not the bird |
“Sapsucker damage is notable because the holes are pecked close together and in rows. Other types of holes are not uniformly aligned.” (Mississippi State University Extension Service, Recognizing Sapsucker Damage in Yard Trees)
A woodpecker excavation is not causing the decay it sits in; the bird found insects in wood that was already dead. Rows mean a sapsucker, and the tree will almost certainly be fine. Random holes with frass mean borers; get the tree looked at. Big excavations mean the question is the dead wood, not the bird.
What the bird is doing
The yellow-bellied sapsucker is a woodpecker a little smaller than a robin that feeds on sap rather than wood-boring grubs. It drills shallow holes through the bark into the living tissue, lets them fill, and returns through the day to lap the sap with a brush-tipped tongue. It also eats the insects the sap attracts.
Because the bird wants sap, its holes look like no other woodpecker’s: small, roughly a quarter inch across, and shallow. They are arranged in neat horizontal rows, often stacked into a band that runs partway or all the way around a trunk or along a big branch. In early spring the holes are round and a little deeper, reaching the sap rising in the wood. Once the tree has leafed out the bird switches to shallower, squarish wells that tap the sugary sap in the inner bark, and keeps them flowing by adding new rows above the old ones. It returns to the same trees year after year.
Birches, maples, hollies, apples, hemlocks and oaks are favorites in the East, but sapsuckers have been recorded on hundreds of species. American holly, American mountain ash, yellow birch, gray birch, black maple and chalk maple, all in the Blue Whale Trees shop, are on that list. The bird breeds across the northern states, into Canada and down the Appalachians at elevation, and winters across the South. So the tapping season depends on where you live: spring and summer in the North, fall through early spring in the South. Along the migration route in between, it lasts a few weeks each spring and fall.
Who else feeds at the holes
A working sap well is a feeding station, and the sapsucker is only its first customer. Ruby-throated hummingbirds follow sapsuckers north in spring and drink at the wells before most flowers have opened. Other birds, squirrels and chipmunks visit them. In late summer and early fall, when few flowers are left, the wells fill with yellowjackets, hornets, paper wasps, flies and the butterflies that prefer sap to nectar. Those butterflies are mourning cloaks, red admirals, question marks, commas and hackberry emperors.
The wasps are drinking at holes the bird made, and they disperse with the first hard frosts. Beside a door or a patio they are a nuisance for a few weeks and nothing more.
Does it hurt the tree?
Rarely. The holes are small and shallow, and an established tree walls them off and grows over them within a season or two. A big tree wearing a few bands of holes needs nothing from you.
The exception is repetition on a small stem. When a bird taps the same young trunk or branch heavily, year after year, the bands of holes can join into a ring of dead bark. A ring is a girdle: everything above it starves. Young birches, thin-barked maples and mountain ash suffer most, and on thin-barked species the wounds can occasionally admit canker or decay fungi. A small, valuable tree that a sapsucker has adopted is worth watching; a mature one is not.
“Stress from intensive feeding can lead to cambium girdling, decline in tree health, and eventual death of the tree.” (Mississippi State University Extension Service, Recognizing Sapsucker Damage in Yard Trees)
What not to do, and the little you can do
- Do not paint, tar or seal the holes. Wound dressings do nothing for a tree, which walls off damage rather than healing it the way skin does, and they can trap moisture against the wound.
- Do not smear sticky repellents on the bark. They injure it, are hard to remove and rarely stop the bird.
- On a small tree that matters to you, during the weeks the bird is active, wrap the tapped section loosely in burlap or stand a cylinder of hardware cloth an inch or two off the bark. Move it if the bird moves, and take it off once the bird has gone so it does not hold moisture or girdle the stem. The same hardware cloth does double duty against rabbits and voles in winter.
- Consider leaving a favorite tree to the bird. Sapsuckers concentrate on one or two trees, and a big maple tapped for years is drawing the bird away from everything else you planted.
- Do not trap, shoot or harass the bird. Sapsuckers, like every native woodpecker, are protected under federal migratory bird law, and harming them or their nests without a permit is an offense.
- If the holes are scattered and frass sits at their openings, they are a borer’s, not a sapsucker’s: get the tree looked at.
Common questions
What makes neat rows of holes in a tree trunk?
A yellow-bellied sapsucker, a woodpecker that drinks sap instead of digging for grubs, drilling shallow holes about a quarter inch across in horizontal rows.
Why are wasps all over my tree?
They are drinking sap a sapsucker released: yellowjackets, hornets and paper wasps share the wells with flies, hummingbirds and sap-feeding butterflies, and they disperse with the first hard frosts.
How do I stop sapsucker damage to my tree?
Not by harming the bird, since sapsuckers are protected under federal migratory bird law. On a small tree you value, wrap the tapped section loosely in burlap while the bird is about and take it off once the bird has gone.
Do sapsuckers kill trees?
Rarely: the holes are small and shallow, and an established tree grows over them within a season or two. A young birch, maple or mountain ash tapped heavily year after year can be girdled by a ring of holes, the one case to guard against.
Sources
(5 references)
- Yellow-bellied Sapsucker: Oklahoma Department of Wildlife Conservation: squirrels, chipmunks, bats and porcupines at the sap wells, and the switch to shallow rectangular wells after leaf-out.
- Yellow bellied sapsucker damage on tree trunks: University of Arkansas Cooperative Extension Service: girdling as a rare outcome, feeding on more than 400 tree species, and the return to the same tree year after year.
- Yellow-bellied Sapsucker: Cornell Lab of Ornithology: the wells, the sap, and the hummingbirds and insects that share them.
- Recognizing Sapsucker Damage in Yard Trees: Mississippi State University Extension Service: the rows that identify the bird, the girdling risk on a heavily worked stem, and the burlap wrap.
- Migratory Bird Treaty Act of 1918: U.S. Fish and Wildlife Service: the birds the act protects, and what taking one without authorization means.
