Is there anything wrong with starting games with such a rule? Some times I just get annoyed by crows, how some players just have like hundreds of them swarming all over the map, ready to swoop in and take an empty city and capitalize. How exactly does a flock of birds take a city anyway?

Any thoughts? I'd like to start another game like it, but not if it's not allowed or the players just laughingly disregard it. I mean, if you want swarms of crows, play another game.