Martins eating decomposed granite

[loco for purple]

For the past two weeks I've noticed the martins eating the decomposed granite in my back yard . First ,it was only the females, but now I've noticed the males doing this. I also believe they are feeding their babies the granite. I hope it doesn't make them sick. I'm assuming they are getting some type of minerals from the granite....

[belpre gary]

I live by the RailRoad track and I have seen the martins picking up small pieces of limestone there, Don't know what they do with it !

[Louise Chambers]

Martins need to supplement their insect diet with calcium and grit - many landlords provide crushed oyster shell (the most beneficial source of calcium) or crushed chicken eggshell, either on the ground in an open area, or in an elevated platform. Females need calcium for good eggshells, and nestlings need it for strong bones.