I had the chance to witness mass mobbing of a Red-tailed Hawk up close at Sapsucker woods this weekend. I heard the sounds of crows alerts and went over to where they were calling. Crows, Grackles and Red-winged Blackbirds were all mobbing this Hawk. Mobbing is a behavior occurs when a predator gets cooperatively harassed by the species it may prey on - especially when that species has young nearby. At one point, the Hawk was in the tip of a small branch (pictured) and kept losing balance when the others would dive at him.
Red-tailed Hawk and Red-winged Blackbird Sapsucker Woods, Cornell Lab of Ornithology Ithaca, New York Canon 7D / EF 100-400mm f/4.5-5.6L IS USM