I'm kind of jealous of your crows. Ours are just basic black...and HUGE. Since there's a pecan orchard behind my house the crows around here like to perch on our roof and slam pecans down in an attempt to open them. Very annoying...and noisy. But.....I've noticed that the more crows we have, the fewer hawks we have around, and the hawks are the real chicken predators around here.