From Grand Theft Wiki
Flying Rats are 200 collectible pigeons located all around Liberty City in Grand Theft Auto IV which Niko Bellic must find and shoot (or blow up). The pigeons are generally found in out-of-the-way areas, but can be easily noticed by the distinctive cooing sound they make and the red glow they're highlighted with. Killing all 200 Flying Rats adds 2.5% to the game completed percentage and also unlocks an Annihilator helicopter on a helipad near Star Junction in Algonquin.
The in game website www.whattheydonotwantyoutoknow.com shows the location of the flying rats. Small dots are one flying rat, while large dots represent two or more. On Happiness Island, the large dot represents six flying rats.
One Flying Rat is not represented on the website. This one is located on the far west/south-west side of Alderney (the far left island), on a construction site.
- Despite the fact that the 200 flying rats gets the player an Annihilator, the helicopter hardly ever spawns if he or she uses the window cleaning platform and has a better chance of it spawning by using a helicopter to reach the top.
- gta4onlineguide.com - contains details for each Flying Rat