What happens when you kill the 'flying rats' in GTA 4?

When playing Grand theft Auto 4 on the XBOX 360, I shot a pidgeon and a message came up saying something like '199 flying rats left in liberty city'.





What happens as you kill the pidgeons? Are there any rewards for killing lets say 50, 100, 150 of them etc.What happens when you kill the 'flying rats' in GTA 4?
once you get them all it unlocks missles for a helicopter plus if your playing on Xbox360 you get achievmentsWhat happens when you kill the 'flying rats' in GTA 4?
You get an achievement as well as your game percentage increases, also you get (from what I've heard) to unlock missiles to use with a helicopter.
They Die !!!!!!

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