I found Cat's best to track worse than anything I've ever tried before!
I just had another thought Helen, what about trying Layer's Pellets? You should be able to buy them wherever you get the chick crumbs from, its chicken feed again, for the bigger birds rather than the baby chicks! Its a bit like the wood pellet cat litter but smaller pellets - and it clumps (prob not as well as the crumb, but it does clump) and it doesnt track like the crumb, and still a good price. Worth a try.