I was out recently on an early morning birding walk with some of my buddies at Lake Elmo Park Reserve. As we hiked across a wooden bridge, we heard a ruckus of crows from across the lake. Several of them were cawing and diving at a tree on the far shoreline. It looked like they had something under attack.
This is called “mobbing behavior.” We call it that; the crows probably call it “Get that enemy out of here!” Birdwatchers pay attention to mobbing because the crows often have something interesting pinned down.
And if you watch, you can sometimes see the target take flight and get a good look at an owl or a hawk that wasn’t visible while it was in hiding.
Sure enough, as we watched, among the black crows swirling over the tree, there appeared a large, light-colored bird that flew toward a tree that was a bit more distant. That must have been the villain in the crows’ eyes.
The crows didn’t give up the harassment. They just moved their attention to the new tree. Their diving and cawing were unabated.
Suddenly that target bird darted out of the tree, right at one of the crows! The crow dodged and ducked out of the way, just avoiding contact. We identified the target bird as a sharp-shinned hawk that attacks and eats birds! This wasn’t a particularly good choice for the crows to be mobbing, at least not so close.
I hadn’t seen a bird that was being mobbed suddenly turn on the mobbers and strike back, and commented on that fact to Val Cunningham, who was one of people in our bird-watching group. She told me about an incident she witnessed several years ago.
Val was walking through Como Park one fall morning and was drawn to the sound of blue jays screaming at something. They were diving around a large fir tree. She said there were only five or six jays, but it sounded like 15 to 20!
In the past, Val had seen a great horned owl in that tree, but this particularly time couldn’t see what had the jays so agitated. She decided to watch to see if the target of all this harassment would finally get tired of it and take flight.
A young jay settled on a branch near the top of the tree. Suddenly, a hawk’s leg reached out of the foliage, grabbed the jay around the midsection, and pulled it back into the branches. Val says it was big, probably a Cooper’s hawk. Things quieted down right away. The mobbing party was over!
Crows and jays are members of the corvid family. But they’re not the only birds that mob predators. We’ve seen and heard chickadees, nuthatches, downy woodpeckers, even robins engaging in mobbing. It takes a bit of experience and discernment for a birder to distinguish mobbing activity from normal chatter in a flock of birds.
One morning, at the Bass Ponds in Bloomington, I was walking along with my friend John near the back of our group, when ahead of us we heard robins chirping. I told John I thought they were just feeding and enjoying the berries, but as we got up to where the flock was, there was a barred owl up in a tree. The robins were not happy about it being there. And they weren’t alone: chickadees and downies had joined them.
Birds have a couple of reasons for mobbing another bird that they regard as a threat. Hawks and owls occasionally grab a nestling. And they’ll take fledglings that aren’t quite accomplished flyers yet. So, the parents want to get them out of the neighborhood immediately.
Another reason that birds join in a mob is to view the predator for themselves. They’d like to definitively know where the threat is, rather than keep looking over their shoulder (wing?) to see if they’re under attack.
Some birdwatchers use this mobbing behavior to bring birds closer so they can see them. They make a pishing sound to draw birds out of a wooded interior so the pisher can get a good look at them. The pishing is supposed to sound like an agitated bird scolding an enemy. Some bird tour guides even play the tape of a screech owl to try to initiate a mob response.
I’ve never liked that technique. In fact, it can be harmful when a nesting bird abandons its nest to see where the interloper is. And that puts their nest at risk to predators.
So, I prefer to let mobbing be a natural event. It’s much more serendipitous if I come across a flock of birds drawing attention to a bird of interest.
And to you mobbers, keep a safe distance lest a taloned leg reaches out of the leaves!
Clay Christensen lives and writes in Lauderdale.