My opinion?! I wouldn't use them. There are better, quicker decomposing things out there to use - like black and white newspapers tore apart.
I wouldn't use fabrics of any size because I use a rototiller and the fabric would get wound up on the tiller causing my *Free Tiller Man* to quit!
I do use leftover strips to tie up my plants during the growing season.
I know I read something about scraps for birds needing to be a certain length or width - but I can't remember exactly what it was. Maybe if they're too long the birds can get hurt...I don't remember. Will our bird lovers know?