Acorn woodpeckers wage days-long battles over vacant territories, radio tag data show. When acorn woodpeckers inhabiting high-quality territories die, nearby birds begin a battle royal to win the vacant spot. Researchers used radio tags to understand the immense effort woodpecker warriors expend traveling to and fighting in these dangerous battles. They also found spectator woodpeckers go to great lengths to collect social information, coming from kilometers around just to watch these chaotic power struggles. Source 8u.