An owl’s gaze is uniquely penetrating. Peer into an owl’s face — there is something almost human about its large, forward-facing eyes. Just how big are those eyes? They are astonishingly large in proportion to the size of the owl’s head.
A Great Gray Owl, which stands two feet tall and weighs 2½ pounds, has eyes larger than those of most humans!
And while an owl’s eyes may look human, their capabilities are superhuman. Enormous eyes help owls to see in near darkness. An owl’s retinal anatomy is similar to that of cats, which rival owls in seeing in dim light.
Owls see well in daylight, too, but their color vision is probably very limited. And the evolution of such large eyes has required a behavioral compromise: an owl’s eyes are fixed in their sockets, so the bird must rotate its neck to look around.
One ornithologist has described owls’ heads as “little more than brains with raptorial beaks and the largest possible eyes and ears attached.”
Great grey owls are impressive predators. They are able to detect their prey and catch it even if it is hiding under more than two feet of snow. And now we know how they do it.
A recent study performed by a group of scientists from the University of California, Riverside, indicates that owls can detect voles under snow by hearing them. And they are able to do it despite being over 160 feet away.
According to the study, a great grey owl might be able to pick up the low-frequency sounds produced by voles as they are digging or moving through the snow. The shape of their face helps here since the ring of feathers surrounding their eyes “filters and amplifies sound.”
“The Great Gray Owl has the largest facial disc of any,“ the study explains. “As size sets the lower frequency of sound that this disc filters, the large size of their disc implies that the Great Gray is specialized for hearing low-frequency sound.”
A big part of this fascinating technique is also hovering. The great grey owl has been observed to hover in the air for 10 to 15 seconds before making an attack.
The scientists believe that this allows them to avoid being distracted by other sounds or misled by the acoustic mirage.
