Of course, Earth Day makes me immediatley think of recycling. That is why this craft by Kaboose makes perfect sense!
Pull a quart-sized milk carton from the recycle bin, clean it and cut a hole in it big enough for a bird but small enough to maintain it’s structural integrity. Then, use a hole punch to create a notch from which to hang the bird feeder. Now, run a string through the hole and tie a knot to secure it. Now, your bird feeder is ready to fill and hang from a tree branch!