Skip to content

Black Woodpecker Cavities Averaged 11.6 Litres and Grew With Tree Diameter

Black woodpecker nest holes in a mature tree trunk
Research · Ecology

Black woodpeckers (Dryocopus martius) create some of the largest bird-made cavities in European forests. A study from Poland’s Augustów Forest measured 136 black-woodpecker cavities and found an average chamber volume of 11.6 litres, with cavity size strongly linked to the thickness of the tree trunk.

The researchers examined cavities in fallen, broken or uprooted trees, allowing the chambers to be measured directly. Around 76% had been excavated in Scots pine, while the remainder were in deciduous trees. The cavities were on average about 45 cm deep below the entrance and 18.7 cm wide inside the trunk.

Pine cavities were generally larger

Cavities in pine had a larger internal diameter than those in deciduous trees. Across all measured cavities, volume ranged from about 7 to 21 litres. Among deciduous-tree cavities, 63% were smaller than 10 litres, compared with 38% of those in pine.

The strongest predictors of chamber size were trunk diameter at the height of the entrance and diameter at breast height. Trees with a breast-height diameter below 40 cm always contained cavities smaller than 10 litres, while small cavities became much less common above that threshold.

Large trees provide larger forest cavities

Black woodpecker cavities are later used by other birds, mammals and social insects, making the species an important source of large tree holes in mixed and coniferous forests. Based on the relationship between tree size and cavity volume, the authors recommend retaining trees above 40 cm in diameter, especially trees containing decaying wood, in commercially managed forests.

Sources and image credit

  1. Zawadzki, G., & Zawadzka, D. (2026). The impact of tree parameters on the dimensions of Black Woodpecker cavities in pine-dominated forests: The case study from Augustów Forest. Journal of Ornithology. https://doi.org/10.1007/s10336-026-02391-8Primary peer-reviewed article first published online 31 March 2026. Measurements of 136 black-woodpecker cavities in Augustów Forest found an average volume of 11.6 litres; cavity size was most strongly associated with trunk diameter at entrance height and diameter at breast height.

Image: Charles J. Sharp / Wikimedia Commons — black woodpecker nest holes in a mature tree trunk at Glambecksee, Uckermark, Germany; representative cavity image, not a tree from the Augustów Forest study. · CC BY-SA 4.0 · Source

About this content: This story was produced with AI assistance within an editorial workflow developed by Wildlife Vagabond. Editorial responsibility remains with Wildlife Vagabond.How AI is used

Ecology

SPECIES IN THIS STORY

Species in this story

Black Woodpecker Dryocopus martius Explore species

Independent research and conservation news archive

Did you find this information useful?

Wildlife Vagabond is independently built and maintained. Voluntary support helps cover source verification, hosting and continued work on research and conservation news.

Support Wildlife Vagabond

The news archive will remain freely available.