Songbird Essentials Bison Nest 2 Mini Nests (SEBISON207) features two small vine nests that's filled with the hair of a Bison. Each nest measures 3.25-inch and you can put them on the ground with the stakes that's included for ground nesting birds. Bison hair is proven to provide warmth as well as comfort for birds. This is definitely essential for your feathered friends especially during nesting season.