According to the pilot, he was maneuvering the helicopter about 1,000 feet above ground level when he noticed a large bird located to the right of his flight path. As the bird started to circle toward the helicopter, the pilot attempted to avoid it by making a sharp left turn. When the helicopter was in a steep left bank, the pilot felt a "thump" in the airframe and cyclic control. The cyclic became sluggish and less responsive than normal. The pilot initiated a controlled descent and landed the helicopter in the median of a highway. An examination of the helicopter by a Federal Aviation Administration inspector revealed that the main rotor blades required replacement. The pilot reported that prior to the bird impacting the helicopter, there were no mechanical malfunctions or failures that would have precluded normal operation