Yes, actually it is a symptom of a highly contageous disease in birds and can spread to rabbits as well. Back in the old days, the issue was addressed with adding calcium but now we know disease is the issue. There was no treatment in the old days, now there is.
Thinning eggshells is a symptom of infection. And it's contageous which means since the bird has not been kept in isolation, the entire flock could become sick. I never put new birds, even chicks, in with my established flock until after they have been in isolation 30 days. A lot of people say 2...