in Thoreau’s Journal:
Stood within a rod of a downy woodpecker on an apple-tree. How curious and exciting the blood-red spot on its hind head! I ask why it is there but no answer is rendered by these snow-clad fields. It is so close to the bark I do not see its feet. It looks behind as it had a black cassock open behind and showing a white under-garment between the shoulders and down the back. It is briskly and incessantly tapping all round the dead limbs, but hardly twice in a place, as if to sound the tree, and so see if it has any worm in it, or perchance to start them. How much he deals with the bark of trees, all his life long tapping and inspecting it. He it is that scatters those fragments of bark and lichens about on the snow at the base of trees. What a lichenest he must be! or perhaps it is fungi make his favorite study, for he deals most with dead limbs. How briskly he glides up or drops himself down a limb, creeping round and round, and hopping from limb to limb, and now flitting with a rippling sound of his wings to another tree.