Eggshells are great for birds

Never put egg shells down the garbage disposal after peeling an egg. They lie in the bottom of your sewer pipes and eventually clog up your pipes leading to a costly plumbing bill.
Egg shells are great for your plants and birds. First thing you do is let the egg shells dry, then crush them into little bits in a brown bag. You can spread them on top of your planting soil or just pour them into your potting soil for later. If you have a snail or slug problem just scatter around the stem to keep them from killing your plant. Egg shells are good for birds too, just scatter crushed shells in the yard. The egg shells give the birds’ that are hatching minerals and acts as free food. If you have any hair clippings you can toss them out too. Birds love gathering hair for making nests.
After you have boiled eggs let the left over water stand and cool. Once cool strain any of the protein pieces out then water your plants with it. When boiling eggs it extracts much of the minerals from the shells and acts as free plant food. You can also make compost tea with this left over water. Compost tea is generally a pitcher of water with compost in it that is aged a few days then poured into the soil around plants to feed and water the plants at the same time.