Red-tailed Hawks are one of the largest and most commonly seen species in Connecticut. The other morning while driving to the Riverside Park Sewage Pond in Hartford, I caught sight of one of these large raptors resting on a city lamp post. Perched beside the hawk was a Northern Mockingbird who was highly agitated and scolding loudly from a safe distance. Having failed to elicit a response, the mockingbird then embarked on an aerial assault which involved multiple pecks to the back of the hawks head and rump. In the end, the Red-tailed Hawk gave up and flew over to a nearby woodland, but not before enduring another strike from an angry Eastern Kingbird.
So why are avian predators like hawks and owls always the recipient of another bird’s aggression? First and foremost, predatory birds provide a major threat to most other bird species, either because there is a good chance of being eaten or an even greater chance of having their young eaten. The behavior they exhibit is called "mobbing" and is done singly or in groups, depending on the species. For those who are not familiar with a bird’s mobbing behavior, it can be recognized by an array of harsh calls, wing fluttering and tail flicking.
Mobbing occurs mostly during the height of the breeding season as a way to distract and encourage a predator to relocate to another area. Also referred to as the ‘move on’ hypothesis (Curio 1978), previous studies have confirmed that predators are profoundly distressed by mobbing and avoid the areas where they have been harassed. The ‘move on’ hypothesis appears to be most clearly linked to territoriality (Pavey and Smyth1998). Learn more about territorial mobbing here;
As you can see from the photographs above, it can appear that predator harassment is risky business. But in reality, birds who participate in mobbing are usually in very little danger. Species that are chosen to be mobbed are done so very carefully. For example, slow moving raptors like Red-tailed and Red-shouldered Hawks are less likely to strike back at an attacker, preferring to move on and save energy. Rarely would you see the same situation involve a Peregrine Falcon or Cooper’s Hawk.
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| Adult Cooper's Hawk in the same area two days later. Where's the mockingbird now? |
Birders should also be aware of mobbing behavior during the winter months. On past Hartford Christmas Bird Counts, I have discovered Northern Saw-whet Owls in woodlands by following the scolding calls of Black-capped Chickadees and Tufted Titmice. David Allen Sibley writes in his book, The Sibley Guide to Bird Life and Behavior; Parids are social, bold, and inquisitive, traits that endear them to humans but make them among the most tenacious and aggressive songbirds when mobbing owls or other predators. Chickadees and titmice usually take the lead in announcing the presence of a small owl.
Mobbing, on a rare occasion, can lead to dire consequences for the intended target. Winter flocks of American Crows often chase Red-tailed Hawks through city streets, forcing them into near-miss situations with telephone wires, buildings and even vehicles. Some, without a doubt, get injured or die as a result of these relentless attacks.
Late last winter, I saw a Great Horned Owl get chased through the Cedar Hill Cemetery by a flock of very angry, noisy crows. When I finally caught up with the flock, the owl hung motionless by its neck, wedged between two branches. Did the owl make a mistake and stay out to long for another chance at a squirrel? If it did, it ended up costing the owl its life.
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| Photo courtesy of Marcel Guerard |
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