By: Wendy Langhans
I remember an amazing scene in one of the early Harry Potter movies, where a “parliament” of various species of owls descends upon the dining hall at Hogwarts, delivering air-borne messages and packages to the students. Each owl somehow managed to drop their package to the right person while avoiding running into each other, not an easy trick in a room full of chattering boys and aerobatic owls.
But for our common local owls, the Great Horned owl and Barn owl, the stakes for hitting their target are much higher. They hunt in a nocturnal world of canyons, dry washes and oak woodlands where, somehow, these owls manage to locate their prey and swoop in for the kill. Those that fail to do so will not survive long. They make it look easy, but have you ever tried to catch a mouse with your bare hands?
But how do they locate their wily rodent prey. Yes, owls have eyes well designed to work in low light. But their real secret weapons are their ears.
Besides having ears on the opposite sides of their heads, some owls also have one ear higher than the other. So depending on the location, sound will reach one ear sooner than the other; some owls can detect a left/right time difference of as little as 30 millionths of a second. When the owl is looking down from a high spot they can locate the source of sound along both a vertical axis and a horizontal axis, much like we locate a spot on a Thomas guide map using letters and numbers. When the sound reaches both ears at the same time – Bingo! – they’re right on top of it.
Recently, laboratory researchers have found that the Barn Owl can detect changes in horizontal location as small as 3 degrees and vertical location as small as 7.5 degrees. To get a sense of how small that is, extend your arm against the far horizon and lift your pinky finger. The width of your pinky finger is 1.5 degrees. Or think about the last time you saw a full moon; it is about 0.5 degrees wide. In addition, researchers mapped the neurons in the auditory portion of the owl’s brain. They found that it functions like a topographic spatial map, with sounds from above triggering the neurons at the top of the auditory center and sound from below triggering the bottom neurons.
How this works in the field remains to be studied, but it makes me wonder how it affects the owl’s choice of flight path over the target? I wish we could ask Hedwig. May she rest in peace.
Our next hike at Towsley Canyon will be on Saturday, August 18 from 8-10 AM. Come join our MRCA volunteer for an early morning bird hike. Towsley Canyon is located on the Old Road, west of I-5 and about 1/4 mile south of the Calgrove exit.
You can listen to stories like this every Friday morning at 7:10 a.m. on "The Hike Report", brought to you by your hometown radio station KHTS (AM1220) and by the Mountains Recreation and Conservation Authority.
For our complete hike and activity schedule and for trail maps, go to www.LAMountains.com .
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