C. An owl.
In literature, in order to help readers understand a notion trying to be conveyed by their writing, an author will frequently make a comparison between two things that are sometimes seemingly unrelated. The author will compare something unknown, which in this case is speaker at a rally, to something that will generally be known, which in this case is an owl perched on a branch, because most people know what an owl looks like perched on a branch in order to create the best visual. This type of comparison is known as metaphor.