Owls Silent Hunters of the Night

Transcription

1 Owls Silent Hunters of the Night This is one suggestion for a one-hour program. Docents are free to present the program in any way they think is effective. You won t have time to go into all the details below; cover the senses and adaptations, and add according to children s age and interest. Take: portfolio, birds case in van, head-and-neck model, birdsong player (from Polly s desk), and the following: Live animals: Taking an owl depends on what owls are in residence and which presenters are qualified to handle. Remember a sheet and water bottle. Mounts: barn owl and family, barn owl skeleton, snowy owl, spotted owl, burrowing owl, screech or long-eared, touchable GHO, also a skunk, pellet box. Program goal: By the end of the program, the children should know: 1. That owls are birds of prey and nocturnal hunters. 2. That owls have special adaptations for sight, hearing, and silent flight 2. That owls are important in our ecosystem 3. That owls and their habitats should be protected. 4. A few cool facts. Intro to Lindsay. Non-releasable animals; hospital and rehab, wild animals vs. pets; come visit on weekends What is an owl? First, what is a bird? Are they all alike? Do they all eat the same thing? What is a raptor? basic attributes of 1) binocular vision, 2) sharp, curved talons, 3) sharp, curved beak Binocular vision: both eyes face forward (not the ability to see far away, as with binoculars, although many raptors can do that, too). Activity: Have kids briefly make binoculars around their eyes with their hands. Then have them hold one finger out in front and alternate opening and closing right, then left, eye to see how it appears that the finger jumps. Binocular vision allows accurate aim. Nocturnal hunters Why? Discuss dual-shift hunting so there is prey for all. Details of an owl s tools and skills. We might ask, as we show students pictures of owls, what they observe that they think might help an owl find, capture, or eat its food. As they mention eyes, facial disk, feathers, feet and talons, beak, we can discuss them. Eyes

2 Nighttime vision: high sensitivity to the smallest amount of light (rods vs. cones, if students are old enough); Note: owls eyes (and the rods therein) are specialized for low-light vision, not for the long-distance acuity of daytime raptors (which requires large numbers of cone cells). Connection: If we sealed the class off in a gymnasium (or MPR)-size space and let in no light, and lit a match, ask if we could read by that amount of light. No, but an owl could (if an owl could read). Large eyes within skull; no room for muscles that move eyeballs; discuss ¾-circle neck rotation; 14 neck vertebrae, twice the number of people and other mammals; Activity: Have kids look forward while holding their heads still. Moving their eyeballs only, can they see the color the child next to them is wearing? Owls can t do that. Activity: Have kids keep shoulders still and see how far they can turn their heads. Limited by our seven neck vertebrae, our chins don t even go as far as our shoulder. Owls go much farther (3/4 of a circle or 270 degrees). Nictitating membrane, working like a windshield wiper, closes over the eye for protection, especially during prey capture. If you have brought a barn owl, thing might be a good time to bring him out. This is a good owl to use in discussion of 1) hearing, 2) nighttime vision, and 3) silent flight, since, with the extreme facial disk and softest feathers, the barn owl represents the height of these abilities. Hearing (this is not something children will observe, but we bring it in when appropriate, usually after discussion of eyes) Facial disk: While good night vision helps owls navigate through obstacles, they find their prey through sound. Facial disk captures sound and funnels it to ear openings under the feathers. Activity: Have kids cup their hands around their ears as presenter talks. Ask if they can hear a difference when they remove their hands. Connection: owls can hear a mouse step on a twig 75 feet. away (find something within their sight lines that would be equivalent to 75 ft.) Ear openings on most owls are not symmetrical. Buried under the feathers (without flaps and not visible), the opening is often higher on one side than the other. (This is the most extreme in barn owls, who have the best hearing.) This allows owls to determine more accurately where a sound is coming from, essentially hearing in 3-D. Since hearing is important, owls can t afford to have loud wings flapping near their heads, so they are adapted to have Silent Flight

3 Owls wings are buffered, having a very soft surface, so that they absorb sound. Connection: I ask how kids dry off after bath or shower run around the house? stand in front of a fan? Of course they mention using a towel, so I remind them that the towel absorbs water. Sound can be absorbed, too. Activity: I use a towel I bring or ask to use a child s sweatshirt. I ask a volunteer to come forward and ask him/her to clap hands once. Then, making sure the hands are far apart, I hold the towel or sweatshirt in between them and ask the child to clap again. Kids can hear how much quieter this clap is, now the sound has been absorbed by the soft fabric. To break up the sound of air flow (remember even wind is loud), owls wings also have a tiny fringe along the leading edge of the wing, and an irregular ruffle at the trailing edge. Daytime hunters such as hawks need to have strong, rigid feathers so that they can fly fast (so fast that coming on their prey quietly isn t as important; they use their sharp eyesight), their feathers need to be very stiff, and not as soft. Activity: Have students close their eyes as you flap a hawk wing and then an owl wing; they guess which is which. Walk around with the wings and have children feel the difference. Activity: Hold a piece of typing paper in one hand and a kleenex in the other (or have children do this) and flap them. Children will hear a difference between the soft paper and the stiff one. Talons Owls capture their prey with their sharp, curved talons. They can do something other birds of prey cannot they can position their four toes so that three toes point forward and one back, often in perching, or move one toe to the back for a two-in-front, two-in-back grip. This gives a nice, wide x-shaped gripping surface. Many owls have tiny feathers all the way down to their toes. This could help in cold weather, such as with the snowy owl or great gray owl, who plunge their feet into the snow. It could also help while capturing prey, such as with a great-horned owl, which hunts 250 different species, some larger than the owl itself, giving some padding to the feet during a possible struggle. Activity: walk around with talons for children to feel. This might be a good time to bring out a GHO, if you have brought one along, since they are such amazing hunters. Beak Like other raptors, owls have a sharp, curved beak for tearing their food. Like other birds, they have no teeth. Birds need to be lightweight, and teeth are heavy, as are the bony jaws in which they d have to anchored. An owl s beak is usually held downward, buried in the facial disk, so as not to break up the sound waves being funneled to the ear openings. Pellets Discuss pellets and show pellet box. Pellets are formed in the gizzard, a grinding organ beyond the true stomach. Once the pellet has passed back to the stomach, it has to be expelled before the owl can eat again.

4 Reproduction (when there is time) Owls find their mates in different ways. GHOs hoot together; then the male brings a rabbit or rodent to the female. Barn owls soar and screech. Some are very noisy and hoot all night long. Owls don t build their own nests. They use one already built by another bird or even a squirrel. Some lay eggs on rock ledges or in tree stumps. The female sits on the eggs while the male brings her food and protects her from attackers. Owls start incubating when the first egg is laid, so some chicks hatch before others. Oldest get the most food, but they don t pick on their younger siblings like hawks do. Parents bring chicks food until they have enough feathers to fledge, at between four weeks and 2-1/2 months, depending on the species. Before they fly, they leave the nest and hop around on nearby branches to strengthen their wings. During this time, they are called branchers. Following is some info about our resident species and mounts. More information on each is in the info packs (including the one on Commonly Used Mounts). This is an area that you can shorten if you need to. Barn owl They are very strongly nocturnal; reported to be the inspiration for the idea of ghosts, since they are white forms flying silently overhead until they scream or hiss. Roost in rural or urban areas; in California, they often choose palm trees (not so good for chicks, who easily fall off the fronds). They are in a different family from other owls, due (in part) to the comb-like ridges on the middle talon, used for preening. Barn owls have the most extreme difference in the placement of ear openings, helping to give them the best of owl hearing. They also have the softest feathers (and most silent flight). They have more clutches of offspring than other owls and can breed throughout the year, and often lay 3-10 (up to 18!) eggs per clutch. If food is more scarce, they lay fewer. They might be called the world s best mousetraps, since a single owl might be able to capture over 50 mice each night. With as many babies as they have, and since fast-growing birds need lots of food (several nice per night per chick), they need all those hunting skills. In different family from other owls, due (in part) to the comb-like ridges on the middle talon, used for preening. Burrowing owl Are all owls nocturnal? Burrowing owls are diurnal; spend most time on ground; nest in ground squirrel or prairie dog dens; eat small mammals and insects. They collect dung to place at entrance to their burrow; it attracts delicious dung beetles and also masks their odor; make sound that mimics rattlesnakes; snakes also eat them. Screech owl

5 The name doesn t fit, since the western screech doesn t screech (though the eastern does)., Have extraordinary camouflage. Put owl up next to tree trunk. Cool fact: Eastern screech owls put blind snakes (a species as well as a description) into the nest to eat nest parasites. Great horned owl Called Tiger of the Nighttime Sky, crepuscular Can eat 250 species. Activity: Ask first what children think GHO eats; you can probably say yes to just about anything they say. Can take prey up to 2-3 times larger than they are; especially love rabbits and skunks. Since they have no sense of smell, like other owls, the skunk smell does not bother them. Also can eat raccoons, armadillos, porcupines, domestic dogs and cats, bats, turtles, young alligators, and on and on. Hunt by walking, wading, dropping down, or flying over. Barred owl Related to spotted owl; common in east, in west in last century; distinctive call Who cooks for you? Who cooks for you all? Lives in riparian areas, eating prey near streams and wetlands. Time-shares hunting time with red-shouldered hawk; they hunt in similar areas, one at night, one during the day. Snowy owl Discuss diurnal owls, tundra, lemmings as prey Spotted owl Discuss habitat destruction (applies also to burrowing owl) Saw whet owl Name comes from call sounding like whetting a saw How owls help us Eating large numbers of mice and other rodents means there are fewer pests to get into farmers fields and storage, or our garages and kitchens. It also means that people can depend on owls to help kill mice instead of using the pesticides that get into our environment. Exploration and discovery time for mounts, wings, etc. (10 min)