Piling bedding

[Sanri0Circus]

So my babies Edward and bingus have recently started making piles of their bedding in the corner of their cage and I'm so confused because when they do it they leave like empty spots of bedding throughout the cage-- is there a reason they do this?

 

[Piggies&buns]

I assume they are on a disposable bedding?
They may just be playing or it’s scattering around while they are running about.
If you cover the cage with hay, they may not move it so much - perhaps worth a try if it is bothering you and you are finding urine puddles in the cage where there is no bedding