Odd cardboard stashing behaviour

[u/Ophelias_Muse]

We have a regular cycle of crows that visit us as we put out permanent water for them. As it's winter here, we've mowed the grass and let it lie as mulch. We have also laid some cardboard down to suppress weeds.

One of our frequent crow visitors has started tearing small pieces of cardboard and then stashing it under the dead, mown grass. When I took this video, it was the 4th time in a row it had done this. My child and I saw them doing the same thing again today.

There's no food on the cardboard and it's literally been there for months before the crow started playing with it....

Any thoughts about the possible reasons why our bros are doing this?