Don't know about in the States but over here many smaller birds will attack predators like crows to protect their eggs or even moreso their young. We don't have that problem too much in our garden. I think the crows and pyes are too wary of the sharp-beaked blackbirds but they do frequently target young stoggies (woodpigeons) and rip them to pieces. Whilst this can be distressing and messy it does keep the stoggie numbers under control to some extent. The parent birds will try their hardest to fend off the crows but the persistence of the bigger birds always wins in the end.