Could drones be used to fire nets at the birds? The birds could be encapsulated so they can't fly away and then either left to starve to death or be picked up for execution later.
Surely it can't be easy to design a reliable system for storing, firing and reloading the nets?
How about designing an extra sticky type of silly string? It could be prayed on the crows until they are unable to fly. All in the form of an aerosol can.