Angry Birds developer Rovio tells TechCrunch that it expects to make over $1 million in monthly revenues from the free-to-play version of its popular bird-catapulting game.

"By end of year, we project earnings of over $1 million per month with the ad-supported version of Angry Birds," Rovio CEO Peter Vesterbacka told TechCrunch.

The iPhone version of the game costs money, but the Android version is self-published and free. The game makes money off ads it serves up to the user. The Android version of the game has been downloaded over five million times from the Android Market. Vesterbacka also told TechCrunch that the Angry Birds series has an 80 percent retention rate, based on the number of players that return to download updates.

Source: GI.Biz