Here is an excerpt from chapter 8 of Theodore Rex by Edmund Morris. Morris quotes some of Roosevelt's writing and calls it ungrammatical. Can you explain what is ungrammatical about the passage?
Musing on the behavior of screech owls, he produced one extraordinary, if ungrammatical, image:
They come up to the house after dark, and are fond of sitting in the elk-antlers over the gable. When the moon is up, by changing one's position, the little owl appears in sharp outline against the bright disk, seated on his many-tined perch