Teachers TryScience

Ask Students

· What makes an owl look like an owl?

· What is an owl pellet?

· When do most owls hunt?

· What is the shape of an owl bill?

The Big Idea

Beak

Holding up the owl skull ask kids:

§ What do you notice about this skull’s beak?

§ The beak looks like a hook. It is used for tearing flesh. The Latin word for “tearing” is raptor.

§ Birds with these types of beaks are called raptors.

§ This is the skull of a barn owl.

§ Beaks are not bone. Beaks are made of keratin – which is the same protein as in hair.

Now show them the toucan skull. Ask them what they think this bird eats?

§ “This toucan eats bananas! In fact, its beak looks a bit like a banana. It uses the serrated edges to cut through the banana peel. The beak is long so it can reach out and grab the banana from the tree – kind of like BBQ tongs.”

Point out the skull boxes on their desks.

§ Tell them they are now going to compare the skulls, and determine what type of food they will eat.

§ They should also note whether the eyes’ orbits are on the side, or front, of the skull.

After about 5 minutes, ask the students about the macaw skull.

§ Macaws eat nuts, and use their beaks like a nutcracker.

§ In fact, owls completely disarticulate (unhinge) their bottom and top jaws. Macaws cannot do this.

§ Raptor like – for tearing

Show students the Archaeopteryx skull.

§ It has teeth! Teeth are very heavy and would reduce the efficiency of flight.

§ No single modern bird has yet been found that has teeth.

§ As a result, birds cannot chew their food. To aid digestion, most birds swallow rocks. The rocks, called gastroliths (GAST-roh-liths), are stored in the bird’s gizzard.

§ Owls are the exception. They do not swallow rocks, and as a result, they cannot grind the bones of the animals they kill. They must cough up owl pellets.

Eyesight

Ask students:

§ “Look at the skull of this owl.”

§ An owl’s eyeballs are as large as yours!

§ Notice the bony rings around the eyes. These are called sclerotic rings (skluh-RAW-tic). They hold the eyes in the skull. Without the rings, the muscles simply could not hold the eyes.

§ If the owl’s head were the size of my head (which would be really freaky), then the owl’s eyes would be the size of grapefruits. If the bone rings were not there the eyes would fall out! That would be really gross, and would make everyone really upset.

At this point, hold the grapefruits in front of your eyes, and drop them.

Tell students

§ “But wait! There’s more!! The large eyes allow the owl to collect lots of light. To an owl, a moonless night seems as bright as this room.”

Next, ask the students to examine the macaw skull and the owl skull.

§ “Where are the owl’s eyes…on the front, or sides, of the head? Where are the macaw’s eyes?

§ The owl’s eyes are in front of the head so that it can judge distance accurately to catch its prey.

§ Eyes in front… predator.

§ The Macaw’s eyes are on the side of the head so that it can detect the smallest of movements.

§ Eyes on side... prey.

§ Eyes on side also mean the prey can see almost 360° around its head without moving its head.

Now, put your two fingers in front of you. Without moving your eyes, move your fingers slowly to the side until you can’t see them anymore.

§ You can see about 180°. Owls can see only 70° around their heads because the bony rings impede the movement of the eyes.

Owls, however, have another neat trick…

§ How many of you have brothers, sisters, cousins, friends, etc., who are always touching you in the car. If I were an owl I could do this… (At this point turn the head of the owl puppet all the way around)!

§ Owls can turn their heads 270°.

§ Owls have 18 vertebrae in their necks. Mammals have only seven! That’s more than twice as many.

§ Binocular vision (70°): 3-D vision.

§ Owl eyes are not balls, but elongated tubes.

§ Sclerotic bone rings – eyes are fixed straight ahead.

§ Many rods/few cones – probably see in B & W.

§ Three eyelids – third lid is called a nictitating membrane (NIK-ti-tayt-ing); protects eyeball from being scratched while hunting.

§ Head bobbing – helps to see movement of prey

Hearing

Tell Students:

§ “Owls are really weird! If you could stick a straw straight through one of your ears, it would come out the other ear (if you didn’t have a brain). Your ears are lined up perfectly.

§ But owls are weird! One ear is higher than the other. That is, they are asymmetrical. This allows owls to hear in 3-D.

§ They can locate and catch bats and insects on the fly.

§ Their ears are located on the sides of their heads.

§ Prominent facial disk acts as a radar disk guiding sounds to the ear openings. Their facial muscles can alter the shape of the disk.

§ Their downward pointing beak helps to increase the facial surface area for better sound collection.

§ In the area of the brain associated with hearing, called the medulla (me-DUH-luh), they have 95,000 neurons. These neurons create a mental image of space where the sound source is located. This is 3 times the number of neurons in the medulla of the crow.

§ The feathers around their ears have no barbs.

At this point, show the Birds of Prey video.

§ It should be cued to the point where a Barn Owl is sitting on a perch in a cemetery.

§ It then moves on to a scientist named Roger Paine. Dr. Paine describes his research into Owl Hearing.

§ Stop the tape after the section where the Grey Owl catches the mouse in the snow.

Feathers

· Comb-like leading edge of the primary wings

· Large-rounded wings increase efficiency of flying

Behavior

· Opportunistic predators

· Prefer to hunt at dusk and dawn

· Even eagles are afraid of owls

· Other birds will mob owls to scare them away

Hunting - review

· Eyesight – binocular

· Hearing – stereo hearing. Owls hear in 3D.

· Special Feathers – combs on wing feathers help to reduce air turbulence. Show kids the wings (if there is time).

Owl Pellet Dissection

Materials:

Resource Manual for Owl Pellet Lab

□ charts

□ owl pellets

□ tweezers

□ hand lenses

□ dissecting probes or toothpicks

□ small containers (Petri dishes, sandwich boxes, film canisters)

□ skull and bone identification charts

□ writing and drawing paper, pencils

□ stereomicroscopes (optional)

□ plastic sandwich boxes (different from those above).

Introduction:

There are two ways to dissect owl pellets, dry or wet. With dry dissections simply use the dissecting probe to carefully scrape and pick away the fur and feathers from the bones and skulls. We will be doing dry dissections in the classroom.

It is important for each student to determine how many animal skulls or parts they have found. Most students will find one or possibly two skulls or skull parts per pellet; however, students we have worked with have found as many as six skulls in one owl pellet.

Digestion – Review before pellet dissection

· No gizzard – owls do not swallow stones (gastroliths) to grind food. That is why a pellet is produced by raptors. It is the bones and fur that cannot be digested further.

· Owls have two stomachs.

Procedures:

· Obtain an owl pellet. Carefully remove the foil wrapping from each pellet while keeping the pellet intact.

· Work slowly to avoid breaking bones.

· Dissect each pellet separately, using the bone-sorting chart and owl keys to identify bones.

· Separate the bones from the fur and other debris in the pellet. Hipbones and upper leg bones with their large ball joints are easily identified. The scapula or shoulder blade, ribs, vertebrae, foot bones, skull bones, feathers and beaks are also recognizable.

· Dissect the pellet completely and save all bones.

· Use one plate to work from, placing clean bones without fur on the second sandwich box.

· See last page for student dissection questions and keys!

· Arrange all the bones from each pellet on a separate 5" x 8" index card and then glue into place. You may choose to show each animal skeleton separately, or organize all bones according to the type of bone. Use more than one card, if necessary.

· Use a bone and skull identification key to determine what animals have been eaten. Teeth are especially useful in the identification process. Mice, voles, and shrews are common finds in an owl pellet and each has a very different type of teeth.

· The bones can be placed on top of their respective images on the charts. Sharing of parts should be encouraged at this time, especially skulls and other major bones.

· Label the card with your team name and add the cards to the display on the wall.

· How did you feel when you first got your owl pellet?

· What did you think was going to happen?

· What was it like trying to sort the bones on the sorting sheet?

· What did you find in your pellet?

· How is the job of doing owl pellets like the job that a paleontologist does?

· What did your owl eat?

· What do you think can be learned from studying owl pellets?

· Why do environmentalists study owl pellets?

· What are the adaptations that make an owl an excellent hunter?