How woodpeckers manage to retract their beak quickly after it got stuck in wood

January 3 – Febuary 28, 2021

Meeting Abstract

98-2  Sat Jan 2  How woodpeckers manage to retract their beak quickly after it got stuck in wood Van Wassenbergh, S*; Pauly, E; Abourachid, A; University of Antwerp, Belgium; University of Antwerp, Belgium; Muséum National D’Histoire Naturelle, Paris, France

Woodpeckers powerfully peck at trees to remove the bark while searching for food, or to create nest holes. Similar to what happens when we hammer a nail into wood, their beak regularly gets stuck. Our high-speed videos of pecking by black woodpeckers (Dryocopus martius) showed that these birds are able to free their beak quickly and seemingly effortlessly. A kinematic analysis revealed what happens shortly after the beak is fully immobilised after impact into the wood. With a view on the woodpecker facing the left, the head rotates clockwise by a few degrees about the quadrate. This head rotation is inevitably linked to a counter-clockwise rotation of the upper beak: while the proximal end is lifted, the tip of the upper beak is retracted. This implies a few degrees of flexion about the nasofrontal hinge. This backward pull of only the tip of the upper beak creates free space between the beak and the punctured hole, and therefore subsequently enables the retraction of the entire beak without substantial shear. The entire process of beak liberation generally takes less than 20 ms. It demonstrates the counter-intuitive value of maintaining cranial kinesis between the upper beak and the braincase in a species adapted to deliver forceful impacts with its beak.

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