Why do Woodpeckers Make Holes in Trees?

posted in: Feeding strategy | 0

“While in Hokkaido we saw a number of trees that has holes drilled into them. Here I am not talking about the excavation that is done for nesting purposes but for foraging. Many woodpeckers eat insects, especially larvae, found under the tree bark. So they ‘damage’ the bark surface to get at their food source. Some woodpeckers also create/drill holes to feed on the tree sap. I have seen similar behaviour in some Malaysian woodpeckers; I have observed the Rufous Piculet (Sasia abnormis) damage the bark of young branches so as to encourage insect infestation and later return to ‘harvest’ the food source.

“Gorman 2015 suggests that type of damage to the tree points to the woodpeckers using it. In Hokkaido we expect that the ‘damage’ we saw can be attributed to the Great Spotted Woodpecker (Dendrocopos major japonicas), White-backed Woodpecker (Dendrocopos leucotos subcirris) or the Black Woodpecker (Dryocopus martius martius); all three of which are known to have this behaviour. The Great Spotted Woodpecker was the commonest we saw, followed by the White-backed Woodpecker; we only heard the Black Woodpecker. Great Spotted and Black Woodpeckers are known to take sap. The White-backed and Black Woodpeckers are known to forage on dead trees (but I observed the Great Spotted Woodpecker also doing this).

“The trees that we saw most affected/used by woodpeckers (see all 3 images) were at Shunkunitai – a ‘wetlands’ site were many trees have been damaged/killed by a storm some year back, leaving dead, tall stumps behind. The table below attempts to compare these three woodpeckers foraging impact on trees, but is taken largely from European observations – this may not be the same for subspecies in Japan.

“We mainly saw some ‘coarse’ damage to trees and vertical gouging (see top image) which is possibly due to Black Woodpeckers. Some tree had a mixture of fine and coarse work (see middle image) suggesting different woodpeckers at work, while other had only fine holes (see bottom image) suggesting Great Spotted or White-backed Woodpeckers.

“I asked our local expert, Takeyoshi Matsuo, for an opinion from his 40 years of detailed bird watching in the region and he commented: ‘I don’t know whether the Greater Spotted Woodpecker and Black Woodpecker make holes on bark to take sap, I have not observed these species obtain sap from the drilled bark. The Black Woodpecker makes long, vertical, narrow slits or oblong holes. The Ainu tribe in Hokkaido trusts Black Woodpecker as a god who makes a dugout canoe. I have seen almost of all bark of a dead tree were stripped off by a Black Woodpecker.’”

Dato’ Dr Amar-Singh HSS
Ipoh, Perak, Malaysia
8 & 10th June 2019

Location: Shunkunitai, Nemuro, East Hokkaidō, Japan

References:
1.
Gerard Gorman. Foraging signs and cavities of some European woodpeckers (Picidae): Identifying the clues that lead to establishing the presence of species. Denisia 36, zugleich Kataloge des oberösterreichischen. Landesmuseums Neue Serie 164 (2015):87-97.
2. Gerard Gorman. Woodpeckers of the World – The Complete Guide. Bloomsbury Publishing 2014.
3. Relevant pages/birds in Handbook of the Birds of the World Alive 2019.
4. Takeyoshi Matsuo – personal communication.

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