A Little Bit More
Hearing in owls is especially acute; they have several adaptations that enhance their ability to hear and locate their prey. Many species of owls have large, oblong ear openings bordered by small contour feathers. These deep, soft feathers can be spread to create a funnel to each ear opening, improving its ability to gather sounds. In many owls, the two ear openings are completely different in shape! This asymmetry helps owls determine the direction and distance from which a faint sound originates.
The broad head of owls further helps these birds locate prey since the ear openings are far enough apart to create a perceptible time difference in the arrival of sounds. Humans use this technique for pinpointing sound without even being aware of what they're doing. It is the slight time difference of sound reaching our ears that tells us that a sound originates from either the left or right. Thus, owls can detect the direction of a sound by keying in on the difference in intensity as the sound strikes each ear. Research conducted with Barn Owls demonstrated that they could locate and capture prey in total darkness with incredible precision using nothing but their acute hearing as a guide.
Owls also have extraordinary sight, with exceptionally large eyes - some even larger than humans - providing great light-gathering ability to help them see in the dark. All of the owls can see in the daytime, but only certain species regularly feed during this period. Most owls are either crepuscular (active at dawn and dusk) or nocturnal and spend most of the daylight asleep in some secluded location. The owl's eyes are fixed in its skull and it must move its entire head to change its line of sight. Despite the owls' binocular vision, they often practice parallactic localization to further improve their depth perception. Parallactic localization is achieved by bobbing and horizontal movements of the head. The object in view thus shifts its relative position against the background, helping the bird judge distance. Hawks and many of the shorebirds are especially well known for this behavior.
Activities
Predator vs. Prey
Objectives: A better understanding of the role of hearing for nocturnal animals
Materials: blindfold
This is an interesting activity that students will see more as a game than a learning experience. As the poster notes, owls have excellent eyesight and hearing that they regularly use to hunt their prey. But it needs to be noted that the prey also attempts to be silent as it goes about its nightly activities. This exercise helps students test first-hand how important sound can be in a predator/prey relationship.
Have one student be the "owl" and stand in the center of a circle about 25 feet in diameter. The other students, "mice" stand on the perimeter and attempt to reach a single item of food, an "eraser" or whatever, at the base of the owl's feet. Blindfold the owl, turn him/her around a few turns in the circle's center to mildly disorient and then select one of the mice on the perimeter (simply point, don't speak) to move slowly toward the food (the mouse is not allowed to rush). The object for each mouse is to reach the food without the owl hearing his/her approach. If a mouse can get to the food without being "caught", that mouse wins and can be the owl for the next round. However, if the owl hears any sound as they approach, he/she simply points to them and they're automatically out (eaten) of that round of the game. The students quickly catch on that stealth is their best strategy but also find it difficult to reach the food without being heard.
This game can be played inside, but works best outside where there are leaves, sticks etc. that add noise to the approach of the mice. If you need to do this inside, you may want to scatter wadded-up paper in the circle to make the mice work harder to remain silent.
Key Concepts
Predator/Prey Relationships, Structures and Functions
Questions
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Posted by Erwin Riedner on March 29, 2006 at 01:04 PM
Q: What mechanisms (neural, etc.) exist in the woodpeckers to protect their hearing when they are banging and pounding? The external and internal racket must be pretty high.
Thank you,
Erwin Riedner
Wooster, Ohio
A: There has been a fair amount written about woodpeckers and their skulls (the bone has a cushioning ability that absorbs the incredible pounding it receives) but I know of no work done on their hearing. It certainly does seem that the pounding noise would be hard on their ears especially since they rely on their hearing, in many cases, to locate grubs within the wood. Take a look at our earlier unit on woodpeckers and their probable use of listening for food at www.enaturalist.org Sorry I can't give you any more information but thanks for asking.
Posted by Laura Bloomfield on March 20, 2006 at 10:55 PM
Q: Hello,
Today I saw a shrike hovering (unsure if loggerhead or northern). I was under the impression that only birds of prey could hover. Do a lot of passerines hover as well?
A: At this time of year, you're most likely to have seen a Northern Shrike in your area but a Loggerhead is always possible. Actually, many birds can hover, not just raptors. I've seen many warblers hovering as they snatch an insect from a branch tip,chickadees and kinglets too, will often hover. Many of the passerines can and do hover at times. Obviously, some are more adept at this than others but don't be surprised when you see it. Thanks for your question.
Posted by Andrea on April 14, 2005 at 11:51 AM
Q: Do blackbirds listen or look for their food?
A: The blackbirds use their vision to find food, not their ears. Although they can probably see a bit at night, like you and me, they rely on eyesight to find their food and, of course, they are active in daylight and sleep at night. Thanks for your question.
Posted by Andrea on April 14, 2005 at 11:50 AM
Q: Which bird locates its prey by ear, slowly turning its head to pinpoint the location before pouncing?
A: Owls regularly use their hearing to help them find food in the dark. In fact, one researcher did an experiment with a Barn Owl in a totally dark room. He found that the owl could home in on a mouse simply by using its hearing. So, they use both hearing and eyesight to help them find food. Thanks for your question.
Posted by Christina Hill on October 07, 2002 at 01:24 PM
Q: How many feathers do the adult owls have all together?
A: Christina
The number of feathers that an owl has depends on many factors but probably no two owls have the exact same number. Just as you probably don't have the same number of hairs on your head as a sister or friend in school, no two owls have exactly the same. But, I can give you some numbers of bird feathers other than owls. Some scientists actually counted the numbers from the following birds to come up with a total. One Ruby-throated Hummingbird had 940 feathers, a Ruby-crowned Kinglet had 1,119, an Eastern Meadowlark had 4,915, and a Whistling Swan had 25,216 feathers on its body. Remember too, that birds have more feathers in cold seasons than in warm seasons so these numbers will vary during the year. Sorry, but I didn't find any feather numbers for owls.