like humans and plants, birds also benefit from calcium; female birds especially benefit as they need extra prior to and after laying their own eggs. to make bird food, line eggshells on a baking sheet and bake them at around 250 degrees until dry. then crush them into fine bits with your favorite seed and either place in a feeder or spread on the ground.
once the shells have dried, poke a hole in the bottom of each using a sharp needle or tool. this will allow for water drainage. place an eggshell in each carton portion; fill each shell with soil. place seeds into the soil, according to the packaging. 