I ordered the polystyrene birds from Yellow Moon with the intention of just quickly painting them and hanging them in the front window.
However, as you can see, the paint didn't cover very well so I had to adjust my methods.
I dug out some tissue paper and glue and shredded two variations of each colour. Then I just glued the paper over and let it dry.
Once it was fully dry I added small hook and eye screws to each of the birds (except the purple one which only has an eye on the top of the bird).
I used a small piece of string to hang the first one and then just connected the others using the hook and eye screws. I've got some left over birds I plan to set out for the kids to do their own mobiles - great process art for them and a finished 'project' for showcasing around the house!