Today's Report Includes: Bald Eagle Migration News Do Male and Female Eagles Migrate Together? Challenge Question #20 Golden Eagle Migration News Challenge Question #19 (Encore): Differences in Juvenile Migration? Fact Sheet: Comparisons Between Golden and Bald Eagles Challenge Question #21: Why Don't Bald Eagles Have Feathers on Legs? Adaptations for Flight: Discussion of Challenge Question #17 How Birds Fly: An In-Depth Primer About Flight Light for Flight: But How Much do Satellite Transmitters Weigh? Challenge Question #22 Bald Eagle Migration News Link to: This Week's Satellite Data Migration Map as of April 17, 2001 "A HUGE move northeast for Eagle E63 on April 8th--and another big move on April 13th!" reports EagleEye Nye. In all of the years we've tracked migration with Peter Nye, only one eagle has gone as far north as Eagle E63 has now traveled. And if Nye's rule of thumb holds true, Eagle E50's late departure date suggests he'll head to the far, far north too. Let's keep an eye on both of those birds! Meanwhile, K72 continues to travel in the other direction--to the northwest. The pattern of all the eagles' travels look like a big fan on today's migration map. Just think: They all spent the winter in New York as neighbors but are now spread across northern Canada. In fact, Eagles K72 and E63 are now 910 miles (1,465 km) apart! Do Male and Female Eagles Migrate Together? Do you think male or female eagles arrive back at their nest site first? Or, do you think they migrate --and arrive at the nest--together? "Many questions surround Bald Eagle migration, some involving male versus female behavior," says Nye. "Although we have only a couple of complete 'stories' to go on, from the work we've done over the past decade or more it appears that males and females migrate back to their nest sites separately." Read carefully what Peter Nye has learned over the years, then see if you can answer Challenge Question #20: Link to: Do Male and Female Eagles Migrate Together? by Peter Nye Challenge Question #20: "Can you find three reasons why Nye believes that males and females of eagle pairs migrate alone rather than together?" (To respond to this question, please follow the instructions below.) Golden Eagle Migration News Golden Eagle #004 was wandering slowly northward as of the 10th. But on the 12th Peter Nye was surprised: "Whoa! Major north-jump for our golden!" he wrote. The range and migration of Golden Eagles are not well understood. Hundreds are counted every fall and spring from various hawk-watch spots in the eastern half of the continent, but their migration routes, and even their breeding range in the east, are not fully known. This is why Peter Nye's study so exciting! In addition, because this is a juvenile eagle we must consider: Challenge Question #19 (repeating from last week): "Why might the migration of a juvenile eagle be different from the migration of an adult eagle?" (To respond to this question, please follow the instructions below.) Comparisons Between Golden and Bald Eagles While Bald Eagles are found only in North America, Golden Eagles live in Europe, Asia, north Africa, and North America. And, while Bald Eagles are usually found near water, Golden Eagles can be found in very arid areas where there is no water for miles! Bald Eagles belong to a group called "fishing eagles." Golden Eagles are not closely related to Bald Eagles, they are more closely related to hawks called "buteos," a group which includes the Red-tailed Hawk. But Golden Eagles look a lot like immature Bald Eagles, from their huge size and 80-inch wingspan to their dark plumage. Golden Eagles have feet adapted to catching their prey on the ground. Their legs are well-feathered, unlike the legs of Bald Eagles. Link to: Fact Sheet: Comparisons Between Golden and Bald Eagles Challenge Question #21: "Why do you think Bald Eagles feather-less legs?" What adaptive advantage do naked legs have for Bald Eagles?" (To respond to this question, please follow the instructions below.) Adaptations for Flight Discussion of Challenge Question #17 We asked, "How many physical adaptations can you list that help make birds light? (Think about birds' bodies from head to tail, inside and out.)" These are some adaptations that help make birds light. Did you think of any of these? Hollow bones Feathers Babies don't grow and develop inside the mothers' bodies. Instead, mother birds lay their babies in eggs to get them out of their bodies as soon as possible. Birds don't have bladders. A bird urinates as soon as it has to, getting rid of the useless weight. (That's why you can't housebreak even the smartest pet bird.) Birds eat foods that are very high in usable calories so they get as many calories as possible from as little weight in food as possible. Seeds, fruits, and meat from warm- or cold-blooded prey are the main food items for birds, and virtually no birds (except the Hoatzin, which lives in South America) eat leaves, which take a long time to digest. Their efficient digestion allows birds to get rid of useless weight very quickly. How Birds Fly An In-Depth Primer About Flight Enjoy this primer about bird flight. Learn about "lift" and airfoils--and try this activity: Link to: How Birds Fly: An In-Depth Primer About Flight Try This! To see how an airfoil works, hold a narrow strip of paper near your mouth and blow across the top. The air moves faster above than below, and the paper will rise. Does this work with a larger piece of paper? Why or why not? Light for Flight But How Much do Satellite Transmitters Weigh? Have you ever wondered about the effect the satellite transmitters might have on the eagles? As you can see from this picture, the transmitter is worn on the eagle's back--almost like a backpack. These backpacks are known as "PTTs", or "platform transmitter terminals". Each PTT package weighs approximately 100 grams (3 1/2 oz.), which is less than 2 percent of the body weight of an average bald eagle. How would it feel to carry such a backpack? Challenge Question #22 "If you wore a backpack that weighed 2% of your body weight, how heavy would your backpack be?" (To respond to this question, please follow the instructions below.) How to Respond to Today's Challenge Questions: IMPORTANT: Answer only ONE question in each e-mail message. 1. Address an e-mail message to: jn-challenge-eagle@learner.org 2. In the Subject Line of your message write: Challenge Question #19 (#20, #21 or #22). 3. In the body of EACH message, answer ONE of the questions above. The Next Bald Eagle Migration Update Will Be Posted on April 24, 2001. Copyright 2001 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form