Until the early 1900s, the pink-breasted passenger pigeon was so plentiful in North America that one flock contained as many as a billion birds. However, within a horrifyingly short time, the bird became extinct. While Native Americans had long hunted the passenger pigeons for food, the birds always replenished themselves. It was not until the European settlers began overhunting them for food for their slaves and for profit that the passenger pigeon population began to decline. These settlers thought there would always be more birds to replace those they killed. However, within fifty years they were proven wrong. The extinction of this lovely bird was caused by the interference of man. Not only were too many of the pigeons shot by hunters, but the forests that the birds relied on for protection and nesting were destroyed.