Bird Migration: The Incredible Journeys of North American Birds (Wildlife Appreciation)

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About the Author ---------------- Naturalist, wildlife photographer and writer Stan Tekiela is the author of more than 175 field guides, nature books, children’s books, wildlife audio CDs, puzzles and playing cards, presenting many species of birds, mammals, reptiles, amphibians, trees, wildflowers and cacti in the United States. With a Bachelor of Science degree in Natural History from the University of Minnesota and as an active professional naturalist for more than 25 years, Stan studies and photographs wildlife throughout the United States and Canada. He has received various national and regional awards for his books and photographs. Also a well-known columnist and radio personality, his syndicated column appears in more than 25 newspapers and his wildlife programs are broadcast on a number of Midwest radio stations. Stan can be followed on Facebook and Twitter. He can be contacted via www.naturesmart.com. Read more ( javascript:void(0) ) Excerpt. © Reprinted by permission. All rights reserved. -------------------------------------------------------- FLIGHT BY DAY OR BY NIGHT Many birds migrate during the day. Some of these daytime migrators rely on rising columns of warm air, called thermals, to help carry them upward. As the sun rises higher during the day, it warms the land and creates thermals. Cranes, storks, hawks and other large birds seek thermals and ride them like elevators to the top. As the air rises higher, it cools and slows down. When birds ascend to the top of a column, they glide off effortlessly in the direction of travel and find another thermal to ride. Swallows, swifts and other birds that eat flying insects migrate during the day, feeding while they fly. Many other birds, such as woodpeckers, jays, bluebirds, robins and blackbirds, make short flights during their trips and stop to feed. Typically, it takes these birds much longer to arrive at their destinations. Daytime migrants usually start the day promptly at dawn and spend their first couple of hours feeding. Migration gets underway shortly afterward, with most birds taking off at around 10 a.m. Many of these birds will feed again at the end of the day before resting for the night. However, the majority of small birds, known as the passerines, migrate almost exclusively at night. Most of these birds start migrating during twilight, about 30 minutes after sunset. Passerines usually migrate by themselves, not in large flocks. Other birds may be migrating at the same time and going in the same direction, but these birds aren’t in an organized flight or making a coordinated effort. Modern radar and radio tracking devices have shown that the numbers of birds migrating at night start to build slowly. It’s not until around midnight that the numbers begin to peak. The a of migrants in the air tapers when sunrise nears, with most of the birds landing before daylight. PERKS OF FLYING AT NIGHT There are a number of good, sound reasons why birds would migrate at night. The obvious reason is that they evolved into this behavior. Because so many bird species today migrate at night, scientists propose that in the past, the most successful birds also migrated at night. They suggest that over time, the descendants of the surviving nighttime migrators became the dominant species. Flying at night allows birds to feed and rest during the day. Each morning the birds will land in a new place that they do not know, making the task of finding food just that much harder. They use the daytime hours to find enough food to fuel the coming night’s activities. The atmosphere at night is much more favorable for flight than it is during the day. At night, the air has less turbulence, which makes it attractive to slow-flying small birds. Typically, nighttime airflows are more flat (laminar), providing better support for birds in flight. Air temperatures are cooler as well, reducing the stress of overheating and dehydration associated with long, strenuous daytime flights. Moreover, birds don’t need to stop as often to cool off, making it possible for them to fly farther each night and finish their trips earlier. In addition, there are fewer predators hunting for birds that migrate at night. And equally important, navigation with the stars is perhaps easier than using geography to plot the course of the route during the day. Read more ( javascript:void(0) )