Egg Stealing

Has anyone else come across this before? My neighbour claims that blackbirds are stealing the eggs of robins nesting in his garden. I find this very hard to believe. I told him that I would suspect it is either squirrels or magpies, both of which we have quite a few of around here and both notorious for egg stealing. His 'evidence' is that he has seen blackbirds go into the bush where the robins nest. That isn't exactly proof, in my opinion.