Crows are incredible smart animals. While I was driving I saw one annoying a rabbit not two weeks ago. All along I was thinking: WTH is that crow thinking?! I mean, the rabbit pose no threat to the crow. The crow doesn't have the claws or the power to kill/carry it. So WTF!? ... Well, It keeps annoying the rabbit until it literally crosses the road RIGHT IN FRONT of me. Had I not applied the breaks, guess what, crow gets rabbit dinner!!!

So... dummies (classical owl) will not work... Kill it. BB gun will work just fine. However, being smart animals as they are, if it survives, it will not come back.

EDIT: I would like to say one more thing though. If you do hit it, and it ends up in your yard or so... Well, it will not die immediately. It most likely will just lay there looking at the empty space. Try not to get near it, or you might get beaked if it has it in it. If you leave it as is, it will eventually die. However, if you want to apply the grace shot, be aware that to hit it in the head may not be easy (too small a target) depending on your aim... I had to put down a bird that a friend wounded and I ended up filling the poor animal with no less than 5 shots... I also was able to scare away a crow by simply throwing a rock at it. I missed him by less than an inch and the animal did not come back!... Like I said, crows are very smart animals, and very nasty.

BBs can easily kill or maim birds. I recommend the use of Airsoft - soft plastic balls with much less velocity than BBs.

I would recommend this to scare off the birds:

http://www.airsoftextreme.com/store/index.php?main_page=product_info&cPath=364_67_534&products_id=1900

At 280fps with 0.2g BBs, they will hurt the birds but probably not do any permanent damage.

I have modified gas pistol that will shoot the plastic pellets near 400 fps which I've used to put the coup d'grace on mice stuck inside traps. The plastic balls will penetrate both sides of a soda can at 10ft. It will easily penetrate one side of a soda can at 25ft - maybe more. So 280fps should be good for hurting, but not maiming or killing. I would not use gas blow back pistol to shoot the bird. An electric powered carbine/rifle makes aiming much easier.

We used these at my last job, should work.
http://www.youtube.com/watch?v=b7F_Oif4SP8&feature=related


Btw, Crows are bitchin'.  They use tools to crack nuts.  I've seen them time 4 way stop lights to lay nuts in the path of vehicles acting like nutcrackers.  Our Crows know the trash collectors route and schedule.  Decent rodent control too.

I really don't mind having animals around.  I wouldn't shoot the squirrels though there's millions of them in our yard too (my friend calls my house squirrelville), and they eat and dig up everything I plant.  They seem to like tilled soil, because they often dig up new plants to hide their acorns.  But I wouldn't shoot them.  I like them most of the time.

The crows are all around the yard caaawing all day long, back and forth, and right outside my window at 5am is a bit much.  But I'm not going to kill them and don't want to risk it, so I'd have to be sure it wouldn't do serious harm before shooting one. 

I've got a handheld BB gun that looks like a beretta.  It's plastic.  It's not C02 powered, and it just cocks like a real beretta- there's no pump.  And I've got .25g airsoft bio BB's.  It will penetrate an apple.  I haven't tried a soda can.  What do you think?

Maybe I should shoot myself in the leg first.