Collect leftover material scraps and string that's too small to work with.
Tip: You can also add hair from your hair brush, feathers, or anything else you think the birds can use to make a nest.
You can find suet cages in the bird seed isle at most stores.
Suet cakes will be in the same isle.
Cut suet cake in half and add it to the cage fill the rest of the cage with your scraps.
Now the birds have food, and material to build comfy nests.