Woodpecker stripes

Many people know that denuded tree trunks and piles of bark scales on the ground at the end of winter are the work of woodpeckers, but have you ever noticed the striped scaling pattern on living pine trees created by the king of the scalers, the three-toed woodpecker? This photo, taken yesterday, shows fresh horizontal stripes created by methodical exploration for the larvae of bark beetles. I know they're fresh because the bark scales were  on top of last fall's needlefall. Close examination of the pattern shows a shallow irregular furrow created by the bird's bill striking sideways blows. I've often watched three toed woodpeckers working industiously across and up and down tree trunks. In this case bark beetle galleries and chambers were hard to find, indicating that the woodpecker did a lot of work for little reward.

Once one knows what to look for, pine stripes are actually fairly common in our local forests. For some reason stripes are usually only on one side of the tree, and that side often faces an opening.

This second photo shows what happens when a woodpecker locates bark beetle larvae under the bark. The stripes merge to form large patches, and if you look closely you can usually find larval galleries and chambers with missing larvae - clear evidence that the woodpecker got a meal. Three toed woodpeckers spend the winter finding and feasting on bark beetles that have attacked dead or dying trees. Evidence of their work is everywhere at this time of the year.

And soon, the sound of drumming will announce the start of the woodpecker breeding season. More on that in a future post.