I'm sure you already worked it out!
But for anyone else wondering, this is what some Quakers do when they are masturbating (I've only seen males drool so far)
First you will hear a weird noise that you haven't really heard before; either a muted, repetitive giggle or a 'shhh, shhh, shhh' scratching noise (like someone colouring in with pencils).
After locating the source of the noise, you'll find a Quaker with a wide stance who has morphed into a puffball, all the feathers on their rump will be erect, and their beak will be slightly open with drops of saliva slowly dripping off their tongue.
They won't necessarily be actively humping something.
It is quite a sight and is nothing more than a sign of a happy, healthy Quaker.