To relieve and ventilate the tree and, as well, to destroy its enemies.

December 2. 

The woodpeckers' holes in the apple trees are about a fifth of an inch deep or just through the bark and half an inch apart. 

They must be the decaying trees that are most frequented by them, and probably their work serves to relieve and ventilate the tree and, as well, to destroy its enemies.

The barberries are shrivelled and dried. I find yet cranberries hard and not touched by the frost.

H. D. Thoreau, Journal, December 2, 1850


The woodpeckers' holes in the apple trees. See December 5, 1853 ("See and hear a downy woodpecker on an apple tree. Have not many winter birds, like this and the chickadee, a sharp note like tinkling glass or icicles?"); December 14, 1855 ("I heard the sound of a downy woodpecker tapping . . . Frequently, when I pause to listen, I hear this sound in the orchards or streets."); January 5, 1860 ("I see where the downy woodpecker has worked lately by the chips of bark and rotten wood scattered over the snow, though I rarely see him in the winter. Once to-day, however, I hear his sharp voice.") see also  Walter Harding, Walden’s Man of Science, VQR (Winter 1981) ("He mistook the distinctive hole-drilling of the yellow-bellied sapsucker for the work of the downy woodpecker,")

I find yet cranberries hard and not touched by the frost. See August 23, 1859 ("The cranberries (not vines) are extensively frost-bitten and spoiled.");  August 29, 1858 ("We saw where many cranberries had been frost-bitten, F. thinks the night of the 23d. They are much injured."); September 20, 1851 ("The cranberries, too, are touched."); September 24, 1855 ("Some still raking, others picking, cranberries. "); December 7 , 1853 ("I sent two and a half bushels of my cranberries to Boston and got four dollars for them.")