If you are unsure if something is a food, a good test is to put it outside and see what happens (most memorably done by Spy magazine in 1989 when they put a Twinkie cake on a NYC window ledge for four days and not even the pigeons went near it!).

I found three stale rice cakes in the back of a cupboard this morning and tossed them onto the lawn, confident some creature would eat them. The crows arrived quickly, took a few bites and passed, as did their bluejay cousins. A red squirrel triumphantly grabbed one, probably excited by how large and relatively light it was, scurried up a pine tree, took a nibble and dropped it to the ground.

I gathered up the rice cakes and presented them to the hens, who have pecked at them with little enthusiasm for four hours. They will probably finish them, but it will take a while. Their diet includes grit and small stones, so they are used to eating things without obvious (to us) nutritional value.

Not food.