Inappropriate Nature

Sometimes at work, I like to listen to nature sounds. I made a few lists before with rain sounds, ocean sounds, forest sounds, and more. There is no music with these, just background nature sounds.

Today I started up my forest sounds list. Apparently some of my sounds are marked as “Explicit” on the Spotify website. As I’ve listened to these before and happen to know there is no music or speech, I wonder what makes them explicit.  Are there birds mating? A squirrel clicking insults at another squirrel?  I’m listening much more closely now.