When a predator or other threat has been spotted, some birds will engage in an activity known as “mobbing”. This consists of a loud vocal assault on the offender, and is commonly accompanied by physical assault such as chase, diving at, and attacking the subject. Although many species have been known to mob, corvids in particular have developed this behavior quite well and appear to employ it frequently.
So why do corvids mob? Consider that predators often rely on the element of surprise to attack their victims. Eagles and hawks pose a real danger to corvids and their offspring if gone unnoticed. However, if corvids notice a predator and launch a vocal and physical assault on it, it takes away the predator’s element of surprise and essentially disarms it.
I was fortunate enough to see this behavior with my own eyes just a few weeks ago. I heard it before I saw it - loud, menacing cawing of crows and the frantic chirping of a bald eagle. When I walked to my window to see the commotion, I was not disappointed. The crows, though considerably smaller than eagle, appeared to be fearless. They worked together to keep the eagle surrounded at all times, often one flying above the eagle with the other flying below. Sometimes they would suddenly drop from the sky and appear to collide with the eagle. The birds were difficult to photograph, as they were flying quickly and somewhat distant, but I grabbed my zoom lens and attempted a photograph anyway:
|Corvid mobbing a Bald Eagle!|
When a group of 40-50 crows came in from the East, perched in surrounding trees, and began to caw loudly, their presence seemed to make the eagle uneasy as shortly after the two crows and one that seemed to be a raven, successfully chased it out of the area.
Last week I witnessed a similar thing happen with a hawk in a Target parking lot, and just this morning saw a group of 15-20 crows mob a large seagull. The gull mobbing took place right outside my window, in the same place where the eagle was mobbed. It’s interesting that I had never once noticed crows mobbing anyone, but since learning about the behavior I notice it all the time.
It should be noted that mobbing does not come without risk. An eagle or other large bird of prey may snatch a flying crow and make a meal of it. But to crows the rewards of mobbing outweigh the risks - often times, the predator will simply leave the area and hunt somewhere else where its prey is less hostile and unaware of its presence.
However, other birds aren’t the only targets of these assaults. Crows have also been known to mob humans and even pets who have given the crows reason to see them as a threat. Researcher John Marzluff found that not only do crows consistently mob people they perceive as threats, but the mobbing intensifies over time. As he notes in his book Gifts of the Crow, young fledglings learn who to mob by watching their parents, and even when the parents are no longer around the fledglings will continue to mob those individuals. And these individuals aren’t soon forgotten – crows have been known to “hold grudges” against people for many years.
Crows may be small relative to people and birds of prey, but they are not to be underestimated. Mobbing is just one way they have proven that they are certainly a force to be reckoned with.