We used to have lots of song birds in our area. Three years ago a red-tailed hawk pair nested in a neighbors fir tree. We were both standing under the tree talking about it when small feathers came floating down and landed around us. No song birds since then, but suddenly lots of crows.
I've got a butt load of song birds around, and the crows. Some times up to 20+ turtle doves on the front lawn, where I put millet. From time to time a hawk will nail dove. That's okay, there's a bunch of them. I think crows go after the eggs of song birds. They sure don't seem to affect the population in this neighborhood from the numbers I get at my feeders and on the ground?