Small birds annoying Blackbirds?

Question

Why do we see small groud birds swooping at Blackbirds all the time? I notice a lot when I'm driving! Why do they do that?

Answer 1

Those blackbirds or "grackles" are nest robbers. The smaller birds,usally in pairs or more,are defending there young and there home. The blackbirds will kill the young but they realy just want the nest. I learned this from making several bird houses just to be taken over by grackles. Now i make them with much smaller entrances the black birds leave them alone and actually dont even attemt to envade.

Answer 2

Are you sure you're seeing blackbirds being harassed and not crows? Crows get mobbed by smaller birds (usually mockingbirds) all the time.