... then there was the other half of the flock, who were nibbling the mortar out of the brick wall of the church. I mentioned this when I posted some of the pics on FB and my daughter (who's a biologist) sent me an article offering two theories about what gets birds to do this. One is that they're eating it for the grit, which helps their digestive systems. The other is that they're eating it for the calcium. I'm leaning towards the latter theory, since it would be easier for them to get grit in their systems by eating sand, which is plentiful around the city and doesn't require "excavation" from a wall.
