Cape Ann is fortunate to have several species of owls living with us. They range in size from the small Eastern Screech to the large Great Horned Owls. Occasionally, a Harry Potter-like Snowy Owl comes down from the Arctic and creates quite a stir on the Cape.
If you are lucky, you may encounter one of these creatures on your walks. One day, I was hiking in the woods when I looked up at a low-hanging branch of a tall, white pine tree. I was startled to see a large, Great Horned Owl, up close and personal. If they have owlets in a nest nearby, a Great Horned can become aggressive toward such a human intrusion. Fortunately for me, the big guy with sizable, nasty-looking talons, just stared at me.
There is always a chance that you may see one in your backyard. A few weeks ago, my wife was working in our flower garden. She noticed some white spots on a Rhododendron bush, looked up, and saw a small owl roosting in the maple tree just above the bush. It was an Eastern Screech Owl taking its daytime rest. The white spots were its droppings.
Through evolution, most owls have adapted extremely well to a nocturnal lifestyle. They have exceptional senses of sight and hearing that allow them to silently swoop down in the pitch dark and capture their prey. As a result, owls are truly the “denizens of the night”.
The first thing you notice about an owl is its sizable, yellow eyes that are unlike those of any other bird. They are forward-facing with a focused gaze that gives the owl its appearance of being “wise”. As a result of this configuration, owls have a wide range of “binocular” vision, or the ability to see with both eyes at the same time. This means that, like we humans, they have the capacity for 3D sight and can visually judge the distance to objects of interest, like a rodent on the forest floor.
Owls do not have eyeballs like ours. Instead, their eyes are in the form of an elongated tube that is held in place by a bony structure. This arrangement does not allow the owl to move its eyes the way humans do. But, to compensate, they have the ability to turn their head up to 270 degrees left or right from the forward-facing position.
There are several features of an owl’s eyes that contribute to their extraordinary night vision ability. First, the enormous size of their eyes allows them to take in more of the ambient light. Their pupils can dilate to a very wide opening which lets into the retina more of that light.
Yet another characteristic that helps their superior night vision is that they have many times more “rods” in their eyes than do humans. The rods are cylindrically shaped, light-sensitive cells. In humans, they are concentrated on the outer edges of our retinas. Because of that, we see low light best when we do not look directly at the source. Not very convenient if you are a night hunter. But, with owls, their rods are clustered in the center of their visual field giving them the ability to easily spot their prey while looking straight ahead.
To complement their extraordinary night vision, owls also have highly refined auditory systems. Like humans, their ears are located at the sides of their heads. They can hear a range of frequencies that are the same as humans. However, studies show that their awareness is focused on the frequencies of the sounds made by their prey moving in the underbrush.
Because, like humans, the owl’s ears are on the sides of its head, there is a very slight time difference in the arrival to each ear of the sound of moving prey. The owl senses this tiny difference as the signals combine instantly in its brain. It knows where to look to spot its quarry, turns in that direction, and sees its prey.
People have always thought of owls as being special. Even in Roman mythology, owls were associated with Minerva, the goddess of wisdom. They were thought to presage events and so were considered to be highly intelligent. As a result, astute, prudent people have always been considered to be “as wise as an owl”.
Some birds, such as corvids (e.g. crows and ravens), and selected parrots, like the African Grey, are indeed highly intelligent. They have been found to be capable of solving complex problems and easily learning to speak human language amazingly well. Owls on the other hand do not show such abilities.
Scientists who have studied owls found that the areas of their brains associated with sight and sound are larger and more complex than that of other birds such as crows. It was observed that 75% of an owl’s brain is devoted to its remarkable vision and hearing senses which are critical to its survival. That does not leave much room in the cortex for problem-solving and communication skills. As a result, owls lack the capacity to think, learn, and improvise like crows. And, unlike crows, they do not form complex social structures and rarely communicate with others of their species.
So, the Romans were wrong about the owl being a wise bird. They are, however, beautiful creatures with a wide set of other skills. That is something that we can all appreciate when we are fortunate enough to spot one in our backyards or while out walking in the woods.
Anthony J. Marolda has degrees in physics, is a Popular Science writer and painter, and lives in Annisquam.