Yellow-Bellied Sapsuckers (Sphyrapicus varius, family Picidae (woodpeckers)) are traveling through Ohio on their way to their nesting grounds. I consider the sapsuckers secretive birds and have never captured a picture of one. I’m grateful to Pat Osterhaus (Cincinnati, OH) for sharing her pictures used to illustrate this Alert.
The sapsuckers mark their passage through our state with rows of holes drilled into trees, which may pose a diagnostic challenge to the uninitiated. Although they look like simple holes, there's more to them than meets the eye.
The sapsuckers peck holes into woody stems to collect and imbibe sap. The scientific literature notes that their holes, commonly known as “sap wells” (or sapwells), may appear on over 250 species of trees, shrubs, and vines. Some online references claim the number is over 1,000 species. Hosts include both deciduous trees and evergreens.
Yellow-bellied sapsuckers may be mistaken for other native woodpeckers, such as the Downy Woodpecker (Dryobates pubescens), which is about the same size. However, downy woodpeckers have a red patch on the back of the head and white feather bars on the wings. Sapsuckers have a red patch at the front of the head and vertical white patches on the wings.
Although their common name sounds like a cartoon character or a derogatory epithet, it describes both the bird and its peculiar feeding habit. The bird’s underside (belly) is tinged yellow. And it’s the only woodpecker visiting Ohio that drinks sap. In fact, it’s the only animal, other than humans, that specifically “taps” trees for sap.
Yellow-bellied sapsuckers are the only woodpecker in the eastern U.S. that is completely migratory. As shown in the map below from CornellLab All About Birds, their distant flights make long-haul truckers look like sluggards.
The sapsuckers spend their summers nesting in a wide swath across Canada and the New England states. They spend winters in the warm climates of the West Indies and all the way from the southern and south-central U.S. down to Central America.
Consequently, yellow-bellied sapsuckers visit Ohio twice a year, in the spring and in the fall. The range map above shows sapsuckers may spend summers in a tiny sliver of the southwest part of the state. I’m assuming they are rare at that time of the year, but I’ve never asked local birders about it.
Sapsucker Feeding Behavior
Yellow-bellied sapsuckers produce multiple sap wells arranged in either horizontal or vertical rows. Noting the arrangement is important because the holes are commonly mistaken for adult exit holes made by a tree-boring insect.
Insect exit holes are typically deeper and appear randomly on tree stems. It would be hard to imagine how tree borers could conspire to create the orderly arrangement of holes produced by sapsuckers.
On small-diameter stems, sapsuckers can remove a substantial amount of bark. Not as much as European Hornets (Vespa crabro, family Vespidae) stripping bark to feed on phloem, but enough to make it important to distinguish the different patterns of damage when diagnosing the true culprit.
Sapsuckers produce two types of holes based on the time of year and tree function. The graphic below illustrates basic tree trunk morphology and function. Water, nutrients, and stored carbohydrates flow up the tree through the sapwood of the xylem. Sugar-rich sap flows up in early spring from carbohydrate storage sites to provide energy for new leaf and stem growth. It’s this sugar flow that we tap to produce syrup for our pancakes. Once leaves start producing glucose through photosynthesis, sugar flows down the phloem to storage sites.
Yellow-bellied sapsuckers drill deep sap wells in early spring to tap the sugar-rich flow in the sapwood. It’s no accident that this occurs at the same time we tap maples. The holes are typically circular.
Later in the spring, once sugars start flowing from the leaves down the phloem, the sapsuckers drill shallow sap wells, often square-shaped, to tap the phloem flow. These shallow sapwells require periodical attention to keep the tree’s wound response tissue from closing the holes.
Obviously, as their name implies, yellow-bellied sapsuckers consume the high-carbohydrate sap collected in their sap wells. However, they also consume protein in the form of insects drawn to the sap. In effect, they enjoy meat and potato meals.
Yellow-bellied sapsuckers aren’t just tied to their sap wells for meals. They’re opportunistic feeders consuming bits of the phloem as they tend their sap wells, and arthropods like ants and spiders crawling on the trunk. They also drop to the ground to forage on insects and other arthropods. Fruit commonly appears in their diet when available. Indeed, research has shown that sap may only make up as little as 20% of the sapsucker’s total diet.
It’s common to observe heavy sapsucker injury on a particular tree while others of the same species standing nearby remain untouched. Research has suggested that the sapsuckers target stressed trees, which may account for why we commonly see heavy feeding activity on landscape trees while the birds turn their beaks up at nearby forest trees.
There’s also speculation that yellow-bellied sapsuckers remember their trees from year-to-year. This myth-conception runs deep. I entered the following into a Google search: “do sapsuckers remember their trees.” The answer returned by Google’s AI Overview was, “Yes, sapsuckers do remember their trees and display strong site fidelity, often returning to the same tree or general area year after year to feed.” However, I’ve yet to find any research supporting this A.I. (Artificial Incompetence?) conjecture.
One thing that has been established by research is that sapsuckers are very good at assessing the quality of the sap before committing time and energy to produce sap wells. Tapping sap with high sugar content appears to be the primary factor behind sapsucker tree selection. It stands to reason that if a particular tree is good eats, the bird will continue to peck sap wells, perhaps joined by others.
More Sappy Perspectives
The Good
Yellow-bellied sapsuckers are considered a “keystone species” in the ecosystems where they breed and spend their winters. Their sap wells serve as a food source for a wide range of large and small animals. Their keystone designation means the birds serve a critical role in two types of ecosystems.
The Bad
The impact of yellow-bellied sapsucker damage has long been debated. A study published in 1974 linked yellow-bellied sapsucker damage to canopy dieback. The author of a 1963 publication speculated that sapsucker damage produced “ring shakes” where the xylem (wood) of the tree separates between the growth rings.
However, it may be a which came first question (the sapsucker or its egg?). Subsequent research indicated that yellow-bellied sapsuckers select trees that are stressed or damaged, which calls into question the role of sapsuckers as a primary threat to trees.
The perception that yellow-bellied sapsuckers cause significant harm to their host trees has generated numerous creative methods to thwart their pecking. A study published in 2007 showed that wrapping sugar maple stems with burlap prevented damage, but this solution is impractical for large trees.
Keep in mind that yellow-bellied sapsuckers are protected under the federal Migratory Bird Treaty Act of 1918 (MBTA). This makes it illegal to kill, capture, or harm them.
The Ugly
Sap leakage from yellow-bellied sapsucker sap wells has been linked to a condition on sugar maple (A. saccharum) that I’m calling the “maple black bark anomaly.” Blackened tree bark is most commonly associated with black sooty molds colonizing honeydew dripping from the back ends of sap-sucking insects such as soft scales, aphids, etc.
However, we occasionally see blackened bark on maples, particularly sugar maple, showing no evidence of being infested by a sap-sucking insect. A USDA 1964 publication connected the black bark anomaly to yellow-bellied sapsucker damage. I recently took pictures of blackened bark on a sugar maple that showed evidence of sapsucker sap wells, although I’m not entirely convinced the holes tell the entire story.
The picture below shows black bark on a sugar maple with no obvious sapsucker damage. Such observations spark speculation that black sooty molds may colonize sap leaking from fissures in maple trees, perhaps associated with freeze/thaw cycles. However, I’ve not found any published research supporting this speculation.
On a side note, the black bark anomaly should not be confused with the so-called “Sooty Bark Disease” caused by the fungus, Cryptostroma corticale. The stress-related disease primarily affects maples.
Digging Deeper
There’s much more to these unusual woodpeckers than I can cover in a BYGL Alert, even a lengthy report like this one. If you are like me and find yellow-bellied sapsuckers fascinating, I’ve included an extensive list of references below for your late-night perusal. You’ll find that although we've learned much about these native migratory woodpeckers, there’s more that we need to learn to fully understand their behavior and true position in our forest and landscape ecosystems.
Selective References
Brooks, R., Hulbert, J. M., Omdal, D., Elliott, M., & Chastagner, G. A. (2022). Sooty bark disease diagnostic guide.
Cornell Lab All About Birds. (2026, April 30). Yellow-bellied Sapsucker.
https://www.allaboutbirds.org/guide/Yellow-bellied_Sapsucker/id
Dority, D., Price, J. J., & Pruett-Jones, S. (2016). Yellow-bellied Sapsuckers (Sphyrapicus varius) alter sap well locations in response to experimentally induced tree damage. The Wilson Journal of Ornithology, 128(3), 619-623.
https://go.osu.edu/yellowbellied
Eberhardt, L. S. (2000). Use and selection of sap trees by Yellow-bellied Sapsuckers. The Auk, 117(1), 41-51.
https://digitalcommons.usf.edu/cgi/viewcontent.cgi?article=23475&context=auk
Erdmann, G. G., & Oberg, R. R. (1974). Sapsucker feeding damages crown-released yellow birch trees. Journal of Forestry, 72(12), 760-763.
https://academic.oup.com/jof/article/72/12/760/4660783
Graves, G. R. (2019). Sphyrapicus varius (Yellow-Bellied Sapsucker) Use of Cotinus obovatus (American Smoketree) in the Ozark Mountains. Southeastern Naturalist, 18(3), 499-509.
http://macroecointern.dk/pdf-reprints/Graves_BioOne_2019b.pdf
Long, A. M. (2011). Orientation of sap wells excavated by Yellow-bellied Sapsuckers. The Wilson Journal of Ornithology, 123(1), 164-167.
Ohman, J. H. (1964). Black bark as an indicator of bird peck defect in sugar maple (Vol. 14). Lake States Forest Experiment Station, Forest Service, US Department of Agriculture.
https://www.nrs.fs.usda.gov/pubs/rp/rp_ls14.pdf
Shigo, A. L. (1963). Ring shake associated with sapsucker injury (Vol. 8). Northeastern Forest Experiment Station, Forest Service, US Department of Agriculture.
Smiley, E.T., Booth, D.C., and Wilkinson, L.W. (2007). Preventing Sapsucker Damage on Sugar Maple (Acer saccharum). Arboriculture & Urban Forestry (AUF) September 2007, 33 (5) 367-370; DOI: https://doi.org/10.48044/jauf.2007.042
Sauer, J. R., Link, W. A., & Hines, J. E. (2020). The North American breeding bird survey, analysis results 1966-2019. US Geological Survey (USGS) Data Release, 1051.
https://ui.adsabs.harvard.edu/abs/2020usgs.data.1051S/abstract
Tate, J. (1973). Methods and annual sequence of foraging by the sapsucker. The Auk, 90(4), 840-856.
https://digitalcommons.usf.edu/cgi/viewcontent.cgi?article=19499&context=auk
