Red-winged Blackbirds are extremely territorial and can get pretty aggressive about maintaining their space. Here a Blackbird is harassing a Turkey Vulture that happened to fly over its territory. The Vulture posed no danger but Blackbirds don’t take kindly to any large bird getting too close.
Their aggressiveness is universal. These photos depict Red-winged Blackbirds chasing a Northern Harrier and a poor Osprey just trying to take his fish back to the nest.
Birds in My Viewfinder 