I did this when my daughter had a new litter of hamsters, way back when (in the early 90's). They loved the bits of fabric and thread for nesting BUT we ended up untangling tiny, fragile baby hamster legs from thread and one ended up with three legs when it was all over; the 4th leg had the circulation cut off for too long. I just can't put out thread for any species after that trauma! I put out small scraps but not thread leftovers.