A squirrel cache, which I believe to have been established by Pteromys volans.
On Prunus sargentii; the catkins are from Alnus hirsuta and perhaps Betula davurica.
I am told that the main difference between Pteromys volans scat and Tamias sibiricus scat is location; the first being a tree dweller, the second being a ground dweller.
Here P. volans scat in the fork of a Salix tree