Fall's Journey South Update: September 22, 2000 Today's Report Includes: Humming Along Fitter and Fatter Morning, Noon, or Night Flight: Challenge Question #4 Help the Hummers on Their Journey South Answer to Challenge Question #1 Follow the Food: Answer to Challenge Question #2 Who Goes There? Answer to Challenge Question #3 How to Respond to Today's Challenge Questions Humming Along Jewelweed, a Hummer Favorite Photo Credit: Elizabeth Howard Ruby-throated Hummingbirds are racing south right now. They stop at flower gardens not to smell the roses but to sip the nectar. The timing of their migration coincides very closely with blossoming jewelweed, so this plant may be a critical source of food for them during fall. Flower nectar usually gives hummers enough energy to migrate, but they often "top their tanks" at backyard bird feeders. People from Canada to Texas and all points in between are noticing the tiny critters whizzing through. From Port Lavaca, Texas, Harlen Aschen wrote: "We are at Feeding Frenzy! Photo Credit: Harlan and Altus Aschen the waist of the hour glass for migrants east of the Rockies and some that come on over the Rockies." Harlen took dozens of photographs of Ruby-throated Hummingbirds dining at his feeder. Hot, dry weather in Texas may be increasing the dependence of hummers on some feeders, but there are always huge numbers of hummers in Texas this time of year. Texas is where Ruby-throated Hummingbirds stop to rest and fatten up. Some will then resume migrating along the Gulf Coast. But most will be striking out over the Gulf of Mexico, flying without a moment's rest over 600 long miles over water--and during hurricane season! Fitter and Fatter To accomplish this amazing feat, Ruby-throated Hummingbirds can almost double their weights. It would be very dangerous (not to mention unlikely) for humans to double their weight just before a marathon race by putting on over a hundred pounds of fat. Lugging around all the extra Hummingbird flight feathers are so thin and delicate that they're almost transparent, yet tough enough to flap a minimum of 4 MILLION times without a break over the Gulf of Mexico on migration. Photo Credit: Harlan and Altus Aschen weight would make our hearts work harder without any benefit, because we mammals can't burn fat very efficiently. But birds are great at getting energy from fat, and hummingbird wings are designed to bear the additional weight without problems. At places where migration-watchers see hummingbirds flying, such as Hawk Mountain Sanctuary in Pennsylvania, the greatest number of hummers are counted during midday hours. This leads us to ask: Challenge Question #4 "Morning, Noon, or Night Flight: Why might hummingbirds migrate more at midday than morning or later afternoon and evening?" (To respond to this question, please follow the instructions below.) Help the Hummers on Their Journey South Adult Male Ruby-throated Hummingbird Photo Credit: Harlan and Altus Aschen Although hummingbirds are incredibly tiny and fragile, they can live for a long time. Scientists found a male wearing a band on his leg who lived over 9 years. It's hard to imagine something so tiny being so sturdy. But strong as hummers may be, they DO benefit when we help them on their Journey South. That's why we try to Unpave the Way for Hummingbirds. You can, too! See: Unpave the Way Answer to Challenge Question #1 "Why do you think people seldom see hawks migrating over open water?" Our bird expert Laura Erickson explains: Hawks have such big wings that flapping long distances takes a lot of energy. To conserve energy, hawks search out thermals and updrafts, which are columns of rising air that birds can circle on to gain altitude. Hawks spread their wings and tail wide to increase the surface area so they rise faster. When hawks are as high as the air current will carry them, they "stream out," setting their wings back like arrows and cruising forward as fast as they can, but losing altitude as they go. As soon as they locate another thermal or updraft, the birds start rising again. However, there are virtually no thermals or updrafts over water. Instead, there's a dangerous phenomenon called a "downdraft." Downdrafts can actually drive hawks lower and lower until they fall into the water. Because it just isn't worth the energy they'd need to fly over a large body of water, hawks don't choose those routes and you won't see them there. Follow the Food: Answer to Challenge Question #2 Last time we asked: "What is the preferred food for each species of hawk? Match each species to its food." The answers are: Broad-winged Hawk: C. (Reptiles and Amphibians) Red-tailed Hawk: A. (Rodents) Sharp-shinned Hawk: B (Birds) Who Goes There? Answer to Challenge Question #3 We asked: "What is the correct range map for the Broad-winged Hawk, the Red-tailed Hawk, and the Sharp-shinned Hawk? Match each to its range map. Considering what they eat, how would you explain each species' range?" Pink = Breeding Range Yellow = Winter/Feeding Range Orange = Year Round Range A. Broad-winged Hawk B. Red-tail Hawk C. Sharp-shinned Hawk Amost all Broad-winged Hawks nest in North America and winter in Central and South America. Broad-wings are reluctant to fly over water. Ones migrating south that end up in Florida rather than Mexico can either backtrack over a thousand miles or just stay put. It is thought that long, long ago, some Broad-wings did get lost over the ocean and ended up in Cuba. There was enough food for them, and rather than take off over water to return to their normal nesting grounds, some of them nested on Cuba and formed a unique population. All Broad-winged Hawks go down from Mexico to South America because there it is warm enough for reptiles and amphibians, their preferred food. Red-tails live year-round over most of their range. Some go farther north to breed, perhaps because by spreading out they can find more food to go around during the critical nesting stage. Red-tails can stay from the northern states and Canada down through the southern US and northern Mexico. They need not travel so far because there are warm-blooded mammals for their food in all those places. The Sharp-shinned Hawk has a huge wintering ground because the birds it eats are everywhere; this little hawk lives many places year-round. Some that breed in the northern forest spend the winter as far north as Minnesota, but other Sharpies travel all the way to Panama. Sharpies that are really good at catching warblers and other neotropical migrants must travel to the tropics to feed on them over the winter. Sharpies that are good at catching jays, blackbirds, sparrows, and other groups that winter in the north can stay farther north with their prey. How to Respond to Today's Challenge Question: IMPORTANT: Please answer ONLY ONE question in each e-mail message! 1. Address an e-mail message to: jn-challenge-fall@learner.org 2. In the Subject Line of your message write: Challenge Question #4 3. In the body of the message, answer the Challenge Question. The Next Journey South Update Will Be Posted on October 6, 2000. Copyright 2000 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form