Seeing the boss in the busy office is as rare as spotting a corncrake in the forest.

corncrake 是由 corn（谷物、玉米）和 crake（秧鸡类鸟）组成的复合词，指一种栖息在农田和草地中的鸟类，学名"秧鸡"。这种鸟因栖息地减少而变得罕见，所以用来比喻罕见的事物。