This is how our Neighborhood Watch (Avian Division) works. Crows are horrible, awful intruders, and will be driven from the neighborhood without mercy by the jays, robins, and little bird auxiliary... unless there's a hawk in the neighborhood (Deb has named him Ethan) in which case the crows start screaming holy terror and lead the gang against him. Apparently the local watch (defined as our bird seed and suet customers) have a small area to defend, the crows feel they own an expanded area, and hawks aren't liked by anybody.