Barn Owl Magic
(Page 3 of 4)
December/January 2003
By Terry Krautwurst
That explains how a barn owl hears a mouse, but how does it pinpoint its victim? Picture the cross hairs in a telescopic sight. To zero in on a target, you line it rip both horizontally and vertically. A barn owl does the same thing, but its "cross hairs" are its ears. Minute differences in the timing and intensity of sound reaching each ear give the barn owl a fix on its prey.
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When a barn owl hears a sound, it turns its head toward the source until the sound strikes both ears simultaneously. That gives the barn owl the sound's horizontal position. Determining the vertical position is a hit more complicated, but vital-without it, that dive for yummy rodent flesh could be a few inches too high (a clean miss) or too low (crash). The secret is in the lopsided arrangement of the bird's ear openings. The right ear opening is lower on the face and tilts slightly upward. The left ear is higher than the right and tilts down. As a result, sounds from above are louder in the owl's right ear. and those from below are louder in the left. The differences in volume tell a barn owl whether a sound is coming from above or below and reveal its exact elevation. When a sound is equally loud in both ears, the source is at eye level.
Perhaps even more remarkable is the barn owl's auditory cartography. As it locates sounds and orients their locations in the landscape with its eyes. the barn owl builds and stores an auditory snap of its surroundings. Each sound it locates. each unique combination of ear-to-ear differences in timing and intensity, is assigned to specific brain cells that in turn link that one-of-a-kind combination to a specific location in space. The next time those particular cells in that particular part As a child, envisioned them as mysterious masters of the night spirits on wings. of its brain fire in response to a sound, the barn owl knows within a degree or so where the sound is coming from, even if the sound stops before the bird turns its head toward it. Thus, only a momentary rustle from a restless rodent may spell its doom.
Conflicting Appetities
The barn owl's impressive hunting efficiency is matched only by its appetite. Barn owls eat small birds, insects, and even bats and lizards. But bite-size rodents are by far their favorite fare. Typically, an adult swallows down (whole) about three to six mice, moles or voles a night. In just one nesting season, two adults and six nestlings will consume more than 1,000 rodents.
