A surprising number of the folks that feed wild birds in their yards include eggshells in their offerings. As a matter of fact, Cornell University reported, in their publication entitled Birds At Your Feeder, six percent of the folks that participated in their annual Project FeederWatch fed birds this unusual offering. Why would folks feed wild birds eggshells?
The reason is quite simple—eggshells are a great source of calcium. All birds require calcium in their diets; however, the need for this mineral is greatest during the breeding season and migration.
There are a number of ways that you can feed eggshells to birds. They can be ground or broken up and incorporated in suet mixtures. You can add eggshell to mixed seed mixtures too. Some people even simply spread them across the ground near the area where they feed birds on the ground.
Whichever way you decide to use them, if you want to be sure they will not infect your bird clientele with a disease such as salmonella, bake them in an over for 10 minutes or so at a temperature of 480ºF.
It is well known that purple martins and blue jays dine on eggshells. If you have seen other species of birds eat them in your yard, please let me know.