A djinn is a being which cannot be seen or heard but can sometimes interact with humans. It is by definition supernatural. Believing in djinns resembles a lot believing in ghosts, witchcraft, pagan deities (spirits of nature, nymphs, ...), or many other superstitions.
Shirk means associating others to Allah. Djinns are associated to Allah by the mere fact that they are supernatural entities.
Hence my question : Is a belief in djinns shirk?
Following comments : I know djinns are mentionned in the quran. I would like the opinion of someone who does not take the quran to be litterally true