I also save feed bags before winter and fill them with leaves in the fall. I use the bags for insulation along the walls of the brooder house and then this time of year I spread the leaves over the snow in each of the pens. That uses up the leaves giving them something to do till greenery starts sprouting and I don't have to buy any more straw.
Have you had any issues with scaly leg mites from the leaves? Several of our birds got SLM this winter, not long after we started using the dried leaves for their litter. My father in law said we probably got the mites from the leaves. Perhaps from wild birds that would roost in the large maple tree the leaves came from. I'd really like to use up the 5 bags of leaves we still have but don't want to introduce any more mites!