What are the crows mulching?

They are mulching their nest.

Through our kitchen window I noticed a couple of crows picking up beak fulls of mulch from a broken bag.

That is a large chunk to carry back to your nest.

The mulch is what grass seed is mixed with, along with water in a large hydro seeding machine, before being sprayed onto a lawn area, or any other place a person needs it.

The bag of mulch belongs to a landscaping friend of ours, who left it on our property.
I am sure the crows are happy to have the mulch to line their nest.