Please answer the following question: Extract the answer to the question from the following context. Question: A bird that sleeps on top of another animal, but does not aid nor cause any damage to it may be engaged in what kind of interaction? Context: Commensalism describes a relationship between two living organisms where one benefits and the other is not significantly harmed or helped. It is derived from the English word commensal used of human social interaction. The word derives from the medieval Latin word, formed from com- and mensa, meaning "sharing a table".
A:
Commensalism