In 1937, an amateur astronomer named Grote Reber built astronomy’s first radio telescope. The telescope, which included among its parts a round metal dish that was 31 feet in diameter, sat in Reber’s backyard in Wheaton, Illinois. He built it in four months with $4000 of his own money and, with it, became the only person in the world working in the field of radio astronomy from 1937 through the end of World War II.
All that time, beneath the starry sky that Reber was studying, owls of all kinds were taking the same principle that made his telescope work and using it to sneak up on mice, bats, and other squeaky prey in the darkness of night.
Reber’s radio telescope depended on the concept of a parabola. A parabola is a curved line; it has the shape of an arch, or of some wine glasses. Inside the curve of the parabola (or inside the glass, if thinking of a nice Riesling helps you picture ideas) is a point called the focus. If a bunch of rays of light or sound waves strike a parabolic object parallel to its line of symmetry, no matter where on the parabola they strike, they’ll all be reflected so that they converge at the focus. It’s like when people stand in a circle and put their hands in the center. Everything comes together. Go, Team Parabola!
Grote Reber used this idea to capture radio waves from space. He stood a receiver where the focus of his telescope’s parabolic dish would be.
As a result, with the receiver standing in the middle of the dish like a bright yellow stalk in the center of a flower, his radio telescope looked similar to the satellite dishes many of us are used to seeing today. At the time, though, it allowed him to confirm what scientists previously had calculated must be true: we are receiving radio waves from the far-off center of the Milky Way.
Closer to home, owls use the concept of the curved line to help them deal with a concern far more important (at least to most of us animals) than deep-space radio wave emissions: dinner. Surrounding an owl’s face is a rounded area of shorter feathers like the Hamburglar‘s mask called the facial disc. The facial disc functions a bit like other parabolic objects; in the case of owls, it focuses sound waves toward the owl’s ears.
Which, of course, are not on the sides of its head.
Owls’ ears actually sit just next to their eyes, inside the curve of the facial disc. However, in total disregard of any notions of symmetry that we were taught to appreciate in high school geometry, owls’ ears are uneven. One ear is higher than the other. An owl can adjust its feathers so that the shape of the facial disc takes this and the direction from where a sound is coming into account, directing the sound waves toward the ears. That’s a good thing, for owls if not for mice. Having ears at different heights allows owls to better determine whether a tasty morsel is hiding up high or down below, making them especially effective hunters.
But what about those “ear tufts” that owls like the Great Horned Owl sport on top of their heads? Turns out that they have nothing to do with owls’ hearing. Birdwatchers and biologists have offered several suggestions regarding their purpose. Perhaps they’re useful for camouflage, mimicry, or species identification. Perhaps they’re an example of nonconformity, of the same kind of spirit that leads a man bent on space exploration to design a 30-plus-foot contraption never used before in the field of astronomy and build it in his own backyard.
Like owls themselves on the trail of mice and rabbits, biologists remain in search of that elusive beast called the answer.