Mesmerizing Feather On A Mobile I Made. Stops And Starts Swinging On Its Own With No Wind.

I take interesting tree branches and create mobiles from them. I hang various beads, feathers, stones, etc...BUT out of nowhere, I noticed a feather on this one particular mobile that swings all the time. It can be still as night and that feather is just swinging away. Funny though, seems when the wind is blowing, the feather just hangs there. Don't forget to turn up the volume as my yard is a bird and squirrel sanctuary. I'll upload the one from night so you can hear the froggies in the pond.