I'm having an odd problem. I have one white racer who has raised a number of clutches. She is the last, very tough, bird left of a series of pigeons who were either hit by hawks or did not return. I have 4 other younger birds, now breeding age. The older bird has been on her nest and recently laid two infertile eggs. I took them. A few weeks later, two other eggs appeared in the nest with the old bird. The third morning, there was nothing in the nest, but there were broken eggs one shelf up. A bird could not have done it. I assumed it was a rat/squirrel and tightened up my security. This morning I found one younger pigeon covered with egg yolk and a broken shell on the high shelf (not in the nest). In the NEST there was an egg with what appeared to be an obvious bird peck at the end. Any ideas what is going on? Could the birds be fighting for prime nesting space and breaking each others' eggs?