Who made mysterious rectangular tree holes? (2024)

Posted by Tom of AskaNaturalist.com | Apr 16, 2014 | Animals, birds, Musings About Nature, Plants, Questions and Answers, Uncategorized | 14 |

The Question: I found these holes in a single tree, amidst dense forest. They were freshly made, with no sign of human footprints (there was snow), but no animal tracks either. They look very man-made, but could not have been. They appeared in a 24 hour period. Could you shed any light on them please?

Submitted by: Mark, British Columbia, Canada

(click on photos and graphics to expand)

pileated woodpecker

The Short Answer: These holes are classic foraging holes of the pileated woodpecker (Dryocopus pileatus), the largest woodpecker in North America (assuming Campephilus principalis, the ivory billed woodpecker, is extinct). The ones you found do look remarkably regular, as if made by a saw or a wood chisel. You must have an exceptionally neat woodpecker in your neighborhood. Carol Hartwig, a retired wildlife consultant who has studied pileated woodpeckers, says pileated woodpeckers often make square or rectangular holes. She speculates that the rectangular shape may be energy efficient. She also notes that the grain of western red cedar (Thuja plicata), which is what your tree trunk looks like, is particularly straight.

“The grain of western red cedar is so straight that when the woodpecker hammers with its bill into the trunk, large, straight pieces are excavated. This results in very square corners and a very clean rectangular shape. Their nest cavities are beautifully oval, however, so they are capable of making different shapes depending on the purpose and the type of wood they areexcavating.”

Your holes are far too close to the ground to be attempts to build a nest cavity. More likely, the bird was looking for insects, its main source of food. Ants and termites are favorites, and beetle larvae and other tasty insect treats would be on the menu as well. Given the size of the hole, I’m guessing the bird was having good luck.

range of pileated woodpecker

Tree Holes are in Demand: One group of researchers observing the nests of pileated woodpeckers saw wood ducks (Aix sponsa) repeatedly attempt to steal a choice pileated woodpecker cavity. The nest already contained three hatched chicks and the male woodpecker remained on guard a short distance away. When a wood duck hen would attempt to fly to the nest tree, the male woodpecker would intercept her and prevent her from going inside. However, the researchers noted one time when the wood duck hen entered the nest as the woodpeckers were off foraging and another time when the duck was so quick to the tree, the male woodpecker was caught off guard. In both instances, the male woodpecker entered the nest, a fight ensued, and the woodpecker eventually expelled the wood duck hen and retook his family’s nest. For animals that nest in tree cavities but can’t excavate their own, like the wood duck, the relatively large nest cavities of pileated woodpeckers are prime real estate.

Sources: Conner, RN, Shackelford, CE, Saenz, D, et al. (2001). Interactions between nesting pileated woodpeckers and wood ducks. The Wilson bulletin, 113(2), 250-253.

CONNER, RN, JONES, SD, & JONES, GD. (1994). Snag condition and woodpecker foraging ecology in a bottomland hardwood forest. The Wilson bulletin, 106(2), 242-257.

Hartwig, CL, Eastman, DS, & Harestad, AS. (2006). Characteristics of foraging sites and the use of structural elements by the pileated woodpecker (dryocopus pileatus) on southeastern vancouver island, british columbia, canada. Annales zoologici Fennici, 43(2), 186-197.

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About The Author

Tom of AskaNaturalist.com

I am the founder and main writer of AskaNaturalist.com.

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    1. Markon April 17, 2014 at 5:12 pm

      Wow. Awesome. Thank you!

    2. Brianon July 6, 2014 at 9:23 pm

      Thanks, I have exactly what is described above rectangular holes and all. Still cannot believe a bird did this. I would have difficulty with a chisel. There were about five of them. Top one looks like a nest.


    3. Philon January 4, 2017 at 9:56 pm

      Incredible- I have 4 or 5 of these in a large cedar tree on my property and was convinced somebody had been down there digging something out of the tree with a tool.
      I hope I can catch a glimpse of this magnificent creature!

    4. Frank T.on March 12, 2017 at 4:13 pm

      I just discovered two of these large rectangular holes in a large white pine in back of my home in SW michigan. They are fresh and the wood chips a re fresh and large. the wood chips are 3 to five inches in length and about 3/4 to 1 in wide. The largest of the two rectangles is about 10 in tall and 4-6 inches wide. below that is a smaller one about the same width but only about 5-6 inches tall and about the same width. My concern for the tree is that these holes penetrate all the way into the center of the tree which is about 22 inches wide.

    5. Glenon April 19, 2017 at 12:46 pm

      Just saw these in a cedar tree on a Maine Island, large splinters and nice rectangular holes, I would like to see the woodpecker. They have almost pecked through the tree and are well into the center of it.

    6. Wm Riestereron April 28, 2017 at 12:27 am

      I have several of those in trees on my property in Manitowoc county , Wisconsin. Anyone who wants to know more can reach me at (920) 901-8071. Seem to be freshly made.

    7. Bertemes Claudineon January 15, 2018 at 2:26 pm

      I saw such rectangular holes,just like those on the photo, on a tree in the Haute-Savoie(french Alps).
      Do you know whether this kind of woodpecker is common in the french Alps.

    8. Tom of AskaNaturalist.comon January 22, 2018 at 7:59 am

      Hi Bertemes, there is indeed a very similar woodpecker in Europe, the black woodpecker, which is closely related to and very similar to the North American pileated woodpecker. As this Wikipedia entry shows, it also makes fairly geometric holes: https://en.wikipedia.org/wiki/Black_woodpecker.

    9. Bird and tree loveron April 8, 2018 at 2:42 pm

      I have these in our backyard this year in 4 of our trees near Binghamton, NY. Will they kill our trees?

    10. Bird and tree loveron April 8, 2018 at 2:43 pm

      I should add that they range from about 5′ to 20′ from the ground.

    11. Tom of AskaNaturalist.comon April 9, 2018 at 9:21 am

      Hi bird and tree lover, I don’t think they will kill your tree unless there are quite a few, and that would probably only be the case if the trees were already starting to rot. Most trees can survive a wound as long as it doesn’t circle the bark and therefore cut off all flow of water and nutrients from the ground to the branches. Of course, opening up a hole in the tree the way the woodpeckers do is likely to increase access to insects and diseases, so it might reduce the lifespan of the tree, but I don’t believe it will kill them in the short term. Tom

    12. Kim Rambowon April 26, 2018 at 8:53 pm

      I have many of these holes in different pine trees and have seen this woodpecker many times here but didn’t know what was making the holes till now thanks

    13. tera McFarlandon April 3, 2020 at 4:18 pm

      We were baffled by several of these on two trees on our daily walk. I couldn’t believe a bird did it because they were so symmetrical. Thank you for your expertise. Now we know they were indeed made by a woodpecker (who visits our bird feeder as well.)

    14. Richard Nedwidekon March 5, 2023 at 3:45 pm

      I’ve had one coming to my front yard now for the past 3 years. Very pretty, about a foot tall..

    Leave a reply

    Who made mysterious rectangular tree holes? (2024)


    What makes rectangular holes in trees? ›

    The Pileated Woodpecker digs characteristically rectangular holes in trees to find ants. These excavations can be so broad and deep that they can cause small trees to break in half. The feeding excavations of a Pileated Woodpecker are so extensive that they often attract other birds.

    Who makes holes in trees? ›

    In forests, tree holes are created either quickly by woodpeckers or more slowly as trees age and begin to decay. Birds like owls, songbirds and parrots, and mammals like flying squirrels and opossums, make homes in the holes of trees because they offer safe environments for sleeping, reproduction and raising young.

    What caused the woodpecker to make holes in the branch? ›

    The most common reason woodpeckers use their beaks to create holes in trees is that they are looking for food. Woodpeckers eat insect larvae that are found beneath the surface of tree bark. Some, like the yellow-bellied sapsucker, drill into trees to feed on sap, as well as any bugs caught in the tree sap.

    Do downy woodpeckers make holes in trees? ›

    Downy Woodpeckers nest in dead trees or in dead parts of live trees. They typically choose a small stub (averaging around 7 inches in diameter) that leans away from the vertical, and place the entrance hole on the underside.

    What made a hole in my tree? ›

    Common causes of holes in trees include wood boring insects and birds. In the case of insects, it is usually the larval stage that feeds within the tree while the adults feed on leaves or other external tissues. In spite of this, it is most often the adult stage that created holes in the bark.

    What is a rectangular hole cut in wood known as? ›

    A mortise is a hole cut into a timber to receive a tenon. There are several kinds of mortise: Open mortise: a mortise that has only three sides.

    What animal makes a square hole in a tree? ›

    The pileated woodpecker's primary food source is carpenter ants. The ants form long-term colonies in the dead wood core of a live tree and our woodpecker whacks a big square hole into the tree to get them. These same holes can be used for many years.

    What are tree holes called? ›

    Hollows and cavities

    Cavities and hollows in trunks and branches are typically the result of decay that followed injury. The injury often occurred many years ago (see photo).

    What kind of bird makes a hole in a tree? ›

    Half of all birds are cavity nesters. Woodpeckers, owls, chickadees, nuthatches, and parrots are among the species that do.

    What does it mean when a woodpecker knocks on your house? ›

    Woodpeckers usually hammer on houses for one of four reasons: Because it makes a satisfyingly loud noise that proclaims the bird's territory and attracts a mate. If the birds are drumming for these reasons, they will most likely stop once breeding has begun in the spring (they don't drum when looking for food).

    Are woodpecker holes bad for trees? ›

    Many homeowners question whether woodpeckers cause life-threatening damage to the trees they drill. In general, the answer is that they do not. Healthy trees can withstand the minor damage woodpeckers cause unless trunks or limbs receive girdling injuries.

    How deep is a woodpecker hole? ›

    Some woodpeckers will only peck the surface of the tree, while others will peck all the way through to the wood beneath the bark. A pileated woodpecker, for example, will make a hole that is about 4 to 5 inches deep, while a red-bellied woodpecker will only make a shallow hole.

    How long does it take a woodpecker to make a hole? ›

    He often starts with a crack in the wood, digging out a gourd-shaped cavity usually in 12–17 days. The cavity is about 3–6 inches across and 8–16 inches deep. The entrance hole is about 2 inches in diameter.

    Do moth balls keep woodpeckers away? ›

    Mothballs have not been proven effective in stopping woodpecker activity. Tactile repellants. Polybutene-based gels are registered for repelling birds from surfaces. These gels are sticky and irritate birds that come into contact with them.

    Do woodpeckers only peck dead trees? ›

    Woodpeckers usually peck at dead or diseased trees/limbs, but they have also been known to peck at buildings, siding, metal, and air conditioners. They are found mostly in or on the edge of wooded areas due to food prevalence and preference for living in or near trees.

    What does a woodpecker hole look like in a tree? ›

    Woodpeckers are cavity-nesting birds, which means they build their nests inside holes in trees. Woodpecker nest holes are typically round or oval in shape and are just big enough for the bird to fit inside. The inside of a woodpecker nest hole is lined with soft materials such as wood chips, leaves, and feathers.

    Can you repair woodpecker holes in trees? ›

    For larger woodpecker holes in trees or for many holes in the tree, treat the woodpecker damage with fungicide and cover the damage with hardware cloth (galvanized mesh). The hardware cloth can be attached to the tree with small bolts. Only cover the damaged area and do not encircle the tree with the mesh.

    What animals make holes in wood? ›

    What are Carpenter Bees? Carpenter bees get their common name from their habit of boring into wood. Sometimes referred to as “wood bees,” carpenter bees do not actually eat wood, but cause damage to structures by drilling circular holes to create tunnels inside wood.


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