I was walking in the yard this morning and heard a group of bluebirds making a racket in one of our big red maple trees, but not using their normal call notes or song. This was more like a chattering and reminded me of so-called “mobbing behavior” by which groups of birds surround a predator and scold it and vent their displeasure. I had a closer look and found the object shown in the photo sitting in a knothole, and apparently enjoying the warm rays of the sun on a cool morning. It was a gray morph eastern screech owl, probably better known to the bluebirds as a serial killer of small creatures.
It was interesting how well this gray morph blends in with the tree bark, which makes one wonder why there is a reddish morph, which we have also seen in our yard.
The mobbing behavior of birds is well known but not well understood in terms of its purpose. Why do birds want to call attention to a predator? Does this train the young, alert the nearby birds, dissuade the predator from using the area, or what? One strange aspect of it that an individual is calling attention to itself, and thereby presumably increasing its own chance of being attacked. So this has been called a form of altruistic behavior, but questioned as such since the surrounding birds may often be siblings, and thus share many genes.
Birders use an imitation of mobbing calls (pishing) to attract birds, although this activity is considered bad for ecology since it interferes with natural behavior. Other birders will play a screech owl call to attract a group of mobbers, another activity now banned in some parks. The effectiveness of these approaches indicates how strongly small birds respond to the presence, perceived or real, of a screech owl.
Screech owls are quite common but not often seen. Listen at night and pay attention to the chatter of birds and you will likely find one nearby.
Bill Dunson, Englewood, FL & Galax, VA