In this section you have eight short passages. After each passage, you will find several questions based on the passage. First, read a passage, and then answer the questions based on it. You are required to select your answers based on the contents of the passage and opinion of the author only.

Passage:

A male jackdaw's courtship behaviour is astonishingly human. All his movements are consciously strained and his proudly reared head and neck are permanently in a state of self-display. He provokes the other jackdaws continually if the female jackdaw is looking on and he purposefully becomes embroiled in conflicts with otherwise deeply respected superiors. Above all, he seeks to impress his loved one with the possession of a potential nesting site, from which he drives all other jackdaws, irrespective of their rank.

Question: Which of the following statements best describes the central theme of the passage ?