FINAL Signs of Spring Update: May 21, 2001
Today's Report Includes:
Barn Swallow Babies
Baby swallows start out inside creamy or pinkish white eggs splotched and dotted with reddish and purplish brown, weighing about 2 grams. They live in the egg for about 2 weeks. When they hatch, the babies' eyes are closed, and they are naked except for some gray tufts of feathers on their forehead, shoulders, head, and back.
Baby Barn Swallows: Question 1
Why do you think the few feathers they have at hatching are all on the upper rather than the lower side of the body?
Nestling in the Nest
Baby Barn Swallows: Question 2
Why do you think that swallows remain in the nest so much longer when they don't have to grow as much? Think about the different places their nests are in and the different foods they eat.
Fledging from a High Place
Baby Barn Swallows: Answers to Today's Questions
After you think about and discuss your answers--including the three questions asked in today's photo captions(ABOVE), compare your with bird expert Laura Erickson's answers here:
A Reminder: The REAL World Wide Web
Have you noticed how really good you feel after reading a Journey North report or animal story, spending time with a beloved pet, or watching backyard, forest, zoo, or farm creatures? Many researchers believe that human beings have a natural bond with other living organisms, and nurturing that bond may benefit our own health. But there's an even bigger reason to share the care of nature and the environment. No matter where you live, you're part of a vibrant, diverse, and extraordinary web of living things. Every living thing depends on this amazing diversity of life ("biodiversity") for survival. This is the REAL world wide web, and we can't live without it.
You've learned about many wonderful things people around the world--including you who help "Unpave the Way for Wildlife"--are doing individually and collectively to protect the planet. Conserving biodiversity challenges us to work toward creating a society in which human needs are in balance with needs of all other living things. Many scientists believe that we are now seeing the greatest extinction since the dinosaurs and other organisms died out 65 million years ago. This rapid, massive extinction affects the natural communities like those tracked in Journey North. It also affects Earth's ability to sustain large numbers of humans. More than 6 billion people using resources at the rate we do are causing serious problems of pollution and habitat destruction.
The Clock is Ticking
Exploding human population means trouble for ALL living things. For example, every new person needs space for housing food, travel, work and other needs. Human needs vary widely from place to place, but a UN survey found that the average person requires about 0.056 hectares (about 2.47 acres) of nonfarm land for daily living, PLUS land for food production. Every billion people that we add to the planet in the years ahead will require 250 million hectares more of agricultural land; most of this land will have to come from what is now wildlife habitat. The UN's projected population of 11.2 billion by 2100 would require creation of new cropland equivalent to more than 80 percent of all forest and woodland in developing countries today. Switching natural habitat to human uses can make the remaining land less valuable to wildlife. When development chops wild lands into fragments, native species often decline because the small remnants do not meet their biological needs. As human population growth continues to push development into wild areas, fragmentation will increase and its effects on wildlife survival will grow worse.
We all need to continue taking time for awareness of what's happening right outside our doors; in the soil beneath our feet; among leaves and branches of the trees; in bodies of water and their shorelines; and in the skies overhead. Phenomenal things routinely take place in the natural world, and we at Journey North are delighted that you joined us to experience the wonders of migration, the renewal of the food chain, and the return of spring to the northern Hemisphere. This is the REAL world wide web, and each of us is an important part.
To access teaching materials and background about this complex and urgent topic, see:
Floating on a Breeze: Discussion of Challenge Question #27
"Why is it important for spiderlings to drift away from the place their mother chose so quickly after leaving the egg sac?"
"The spiderlings must move away because of the food supply. There would not be enough food for all of those spiders in one place. Food is a reason why animals must migrate to other places," wrote Evan from Mrs. Koontz's third grade at Rockledge Elementary School in Bowie, Maryland. That's exactly right! If every one of the spiders from an egg sac had to live in one area with all the others, they'd have trouble finding enough food for all of them. Baby spiders disperse so they won't be competing with one another.
Sky High: Discussion of Challenge Question #28
We asked you to read "A Spider's Life and then answer this question: "How can baby spiders with no ability to fly on their own power get as high in the air as airplanes can fly?"
While spiderlings are still very tiny, they climb to a branch, fencepost, or other tall object and tilt their spinnerets up into the air. The breeze pulls silk threads out of the spinnerets-these threads form a "dragline." The spider is still very tiny and light, and when the thread gets long enough, the wind suddenly plucks it up, along with the spiderling at the other end, and carries them away! This works because the spiderling is so light and its dragline long enough to give them a lot of surface area for their weight. The same principle also carries kites aloft on those spring breezes!
Spin Cycle: Discussion of
In our last report we asked: "Why do you think spider silk is so very strong?"
The proteins that form spider silk make it the strongest natural fiber known. Spiders use their silk throughout their lives, for so many reasons that even spiders who never build webs couldn't survive without it. Here are some of the ways that spiders use this amazing fiber:
Some birds, like hummingbirds, take advantage of this powerful fiber for building
their nests. But spider webs are so strong that sometimes hummingbirds get entangled
Trapping Food Many Ways: Discussion of Challenge Question #30
"Why do you suppose spiders that use webs to catch food have poorer vision than spiders who get their food in other ways?"
Hooray for Brady, who had the answer: "I think the spiders that have to catch their prey in the web can feel the prey trying to get out of the web. They don't necessarily have to see to find their prey. The spiders that have to catch their prey other ways don't have the web to feel they prey when they get caught."
Brady is right. Spiders that weave webs can feel the vibrations when an insect or other small animal becomes entangled in the web, so there is no need for them to see well in order to hunt successfully. Some web-building spiders that live deep in caves don't have any eyes at all! Spiders that don't weave webs have to hunt visually, and depend on their eyes for finding food.
Aerial Plankton: Discussion of Challenge Question #31
"Why would there be more insects and spiders floating in the air during daytime than at night?"
During the day, the sun produces thermal air currents that can hold many things aloft. Thermals are strong enough to hold up huge hawks and eagles as they migrate, so they can certainly hold up a tiny insect or ballooning baby spider! Also, winds and updrafts are much stronger in the daytime than at night, making it a breeze for more insects and spiders to float away.
Watching a Spider: Discussion of Challenge Question #32
Laura Erickson told us about her spider and we asked: "Why would a spider be attracted to the moisture of a daily shower?"
Laura thinks the reason her spider came near the shower every morning was to soak up the moisture to keep its blood pressure high enough to be a good walker. Here's why she thinks that: When Laura researched spiders, she found out something weird about their legs. They walk by moving the first and third legs on one side of the body and with the second and fourth legs on the other side of the body. They have muscles that bend the legs at the joints, but they DON'T have muscles to straighten the legs again! To straighten their legs, spiders use their blood pressure. BUT if spider bodies don't have enough fluids, their blood pressure drops, the legs draw up under the body, and they can't move!
Year-End Evaluation: Please Share Your Thoughts!
Please take a few minutes to share your suggestions and comments in our Year-End Evaluation Form below. The information you provide at the end of each year is the single most important tool used to guide our planning.
This is the FINAL Signs of Spring Update. Thank you for traveling along with us this migration season. We hope you've enjoyed this celebration of spring--and that you'll join us again next year!
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