Night owl: how barn owls on the prowl use sound, light, and silent flight to snag their prey.

DID YOU KNOW?

* An Inuit myth says that the short-eared owl was once a young girl who was magically transformed into an owl with a long beak. The bird lost its long beak when it became startled and flew into the side of a house, flattening its face.

CRITICAL THINKING:

* The forests of the Pacific Northwest are critical to the survival of spotted owls. But the lumber industry depends on those forests too. Discuss: Can the two sides coexist?

CROSS-CURRICULAR CONNECTIONS:

LANGUAGE ARTS Have pairs of students each research a different owl species. Then, have one student play an owl and the other, a talk show host. Stage an interview that will teach other students about their owl species.

RESOURCES:

* Grolier search term: barn owl 

* Be sure to check out the great variety of information at The Owl Pages, Visit: www.owlpages.com

High above a field, a common barn owl, Tyto- alba (TIE-toe AL-buh), soars in a nighttime breeze. Suddenly, the bird's expert ears pick up a faint squeak below. Its eyes pan the ground and spy the source of the sound: a delectable morsel, a mouse. The owl pumps its wings silently through the air. In seconds, it nabs its surprised victim. Dinner!

Watching from below, scientists like Eric Forsman of the U.S. Forest Service study these raptors (birds of prey). Their goal? To learn about owls' hunting techniques, habitat needs, and threats to their survival.

Many of these silent stalkers are listed as endangered species (in danger of dying out)--from the barn owl found on every continent except Antarctica, to the northern spotted owl, Strix occidentalis caurina (stricks awks-ih-den-TAL-is cohr-EE-na), of the Pacific Northwest. That's because suitable habitat is disappearing to make way for development. Animals preferring similar habitats are forced to share the land and compete for food and shelter. "In Washington State, the population of the northern spotted owl has declined dramatically in the past 10 to 15 years. We suspect it's because barred owls, Strix varia (stricks VEH-ree-ah), have invaded the region," says Forsman.

When animal populations shift, it can upset the balance of an ecosystem (system of interactions between living and nonliving things), says Marge Gibson, executive director of the Raptor Education Group in Antigo, Wisconsin. Example: Barn owls keep mice populations in check. "They're the princes of rodent control," Gibson says. Losing their habitat to animals that don't hunt rodents means mouse populations may rise.

Indeed, barn owls are champion hunters. They skillfully snap up one-and-a-half times their body weight in prey each night.

DIRECTIONS: Answer the following in complete sentences.

Define the following terms:

1. Raptor: --

2. Endangered species: --

3. Nocturnal: --

4. Explain why scientists feel that barred owls are responsible for the decline of the northern spotted owl in Washington State.

5. Describe three adaptations that allow a barn owl to hunt efficiently during the night.

ANSWERS

Night Owl

1. A raptor is a bird of prey.

2. Endangered species are species that are in danger of dying out.

3. Nocturnal means active at night.

4. Scientists believe that the barred owl, "evicted" from its natural habitat, has invaded the Pacific Northwest. They are now competing with the spotted owl for space and food.

5. A barn owl has a facial disk that collects sound waves, bouncing them back to the owl's ears. Because the owl's ears are asymmetrical, the owl's brain can calculate exactly where the prey is located. The barn owl's eyes have large pupils and more rods, which make them 100 times more sensitive in the dark than human eyes. The barn owl's wings are designed for silent flight.

SILENT WINGS

Barn owls have the uncanny ability to swoop down noiselessly on their supper. "If it wasn't for silent flight, owls would starve. They wouldn't be able to catch anything, because their prey would [hear them and] run away," says Gibson.

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That's why the front edge of an owl's wings sports a comblike fringe of stiff feathers. The comb's "teeth" break up turbulence (irregular air currents), smoothing airflow over the wing. The less an owl disturbs the surrounding air molecules (particles of two or more atoms joined together), the quieter its flight will be. The raptors also have a covering of downy feathers on their wings that help muffle the sound of their movements.

SUPERSIZE EYES

Owls have some of the largest eyes per body size of any animal. "If humans' eyes were similarly sized, we would have eyes the size of tennis balls or larger," says Gibson.

An owl's extra-large pupils (opening at the eye's center) and an abundance of rods (cells that detect light) make the raptor's eyes about 100 times more sensitive in the dark than human eyes. That's important for nighttime hunting. But having such huge eyes has one drawback: Owls can't "roll" their eyes from side to side in their eye sockets like humans can. Instead, they have the handy ability to rotate their heads 280 degrees--almost a full circle.

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RADAR HEAD

Barn owls are nocturnal (active at night), so hearing their next meal is more important than seeing it. An owl's facial disk--the flat feathers surrounding its face--collect sound waves (vibrating energy waves that travel through a medium) just like a radar dish does. These feathers bounce sounds back to the owl's ears, or the slits on either side of its head.

These openings are asymmetrical, with the left ear positioned slightly higher than the right, so sound waves enter one slit a fraction of a second sooner than they hit the other. The owl's brain calculates this time difference to tell whether its prey is left, right, up, or down.

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