I was just told by a sewing friend she puts her scrap pieces of thread in a basket hanging from a tree. The birds love it to build their nest. The humming birds are drawn to it because of the bright colors. I tried it and it works...

PLEASE don't put thread out for the birds! It seems like a nice thing to do, but the thread can tangle around babies' feet, wings, etc and they die. They can't snip them off as they can with grasses. In the 60's it was common to cover pet birds' cages at night with a towel, and there were incidents of limb strangulation and even choking. I've seen a bird with foot gangrene from thread- it's horrible. Poly never rots, and cotton takes a long time unless buried.

I didn't read all the posts (my bad) but it can work in your serger if you have one. I've been told anything you can get through the eye of the needle will work in the serger.

I think they meant in the loopers.

You can put thread in your compost pile.

I use all of my cut off (starting/jumpthreads) pieces of embroidery thread when I make fabric for journals/totes etc...