City Simulator - partial

I wanted to emulate one of my favorite games the best i could. It has a few unique features like birds freely flying around the city(animated), sometimes they seem to flock (but the biod system isn't too advanced, they see other birds and objective-points but not buildings). IF ANYONE CAN COME UP WITH A GOOD CITY GROWTH MODEL PLEASE HELP. The current city growth is based on a crappy crime equation i came up with. (Crime = (PopCount / 4) - (2 * SafetyCount))