Another view is that many species originated in temperate zones and evolved to spend the colder part of the year in the tropics. One example, according to Peter Berthold, former director of the Max Planck Institute for Ornithology in Radolfzell, Germany, is the sojourn of a population of marsh warblers that travels from northern Germany to East Africa and spends several weeks there before heading to South Africa. Are these migratory behaviors written into the genes, steering birds like automatons to their destinations?
Or do young birds learn from adults where to migrate and how? The ordeal of flying nonstop from Alaska to New Zealand is hard for the human mind to comprehend, so when Gill talks to grade school kids about bar-tailed godwits, he uses a gimmick to get them to imagine the endurance needed to make that journey. Like other long-haul migrants, godwits prepare by building enormous reserves of fat in the weeks leading up to their departure.
The equivalent of gasoline, fat is what fuels the birds. When the godwits leave, more than half their body weight is fat. They look like feathered croquet balls, with a layer of fat under the skin up to an inch thick and more fat encasing their abdominal organs.
As they fatten up, their pectoral and leg muscles also grow larger. Other long-distance migrants, such as red knots, shrink the gizzard and other organs in preparation for flight—the equivalent of jettisoning excess cargo. The birds tend to depart from Alaska on the tail end of storms that produce winds blowing south. Their departure from New Zealand also coincides with favorable conditions for traveling. Researchers assume that godwits, which are not known to soar, flap their wings for most of their journey, even when riding winds, while other species, such as albatrosses, do soar.
Some species possess an astonishing flexibility in regulating their sleep. The researchers, capturing frigatebirds in their nests, implanted sensors to track brain electrical activity and glued data-recording devices on their heads before releasing them. Besides keeping track of location and altitude, the devices helped the researchers determine sleep patterns. The data showed that the birds slept in short bursts lasting an average of 12 seconds, usually while soaring, that added up to an average of 42 minutes a day.
That was a mere fraction of the 12 hours a day the birds slept when they were in their nests. For a substantial part of the time that they napped in the air, the birds only put half of their brain to sleep, while keeping the other half awake. To learn whether godwits rely on similar sleep patterns in flight, researchers need considerably smaller batteries—a goal Rattenborg says is within reach. He once photographed a desert wheatear, some populations of which divide their time between breeding grounds across Central Asia and wintering habitats from North Africa to India.
Scientists looking for the secret to this capability have found evidence of not one but several mechanisms birds appear to use.
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Migrating birds use a variety of navigational cues—the sun, landmarks, stars,. Though some migrate. In a German scientist named Gustav Kramer discovered that European starlings relied on the sun as a compass. Then, in the s, Stephen Emlen, an ecologist at Cornell University, put indigo buntings in a planetarium and showed that, like ancient mariners, birds also look to the stars to navigate.
Around the same time, laboratory studies of European robins by a German zoologist couple, Wolfgang and Roswitha Wiltschko, discovered that birds possess an internal magnetic compass. Mouritsen, along with two colleagues—William Cochran and Martin Wikelski—conducted an experiment in to investigate navigation in thrushes migrating in the wild rather than hopping around in a lab.
The birds, fitted with tiny radio transmitters, were set free at night, after no sunlight remained in the sky. Traveling in cars equipped with antennas to track the birds, the researchers followed them for up to miles. As it turned out, the birds flew west instead of north on the first night of their travel. But on later nights, the same birds flew north, as they were supposed to.
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From this behavior, the researchers inferred that the birds were orienting themselves using their magnetic compass, but calibrated it daily with twilight cues from the sun. Nor is the magnetic compass a reliable fallback everywhere. But Mouritsen speculates that, like the thrushes in his outdoor experiment, godwits rely on their magnetic compass and reset it every time the sun is visible.
Like the godwit, it breeds in the extreme north and flies thousands of miles south for winter. It forages along the shore by sticking its slender bill in the mud to find mollusks.
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When had they become primarily vegetarian and why? The researchers found that these red knots were juveniles, with shorter bills and smaller bodies than usual. They also discovered that the body size of juveniles varied considerably by year. Those born when the Arctic experienced the warmest temperatures had the smallest bodies and the shortest bills. The red knot study is one of a few that offer concrete evidence of how climate change and environmental damage may be harming migratory species.
Populations of many seabirds have shrunk drastically over the past half century, while shorebird populations in North America have crashed by 70 percent since Some of the sharpest declines have occurred in species that use the East Asian-Australasian Flyway—a group that includes knots, sandpipers, and godwits. A leading cause for this appears to be the ongoing destruction of stopover sites along the Yellow Sea, where the tidal mudflats that sustain the birds are being filled in at a frenetic pace to build ports, factories, and housing.
Similarly, illegal hunting and changes in land use have imperiled migrants that journey between Europe and Africa, and between North and South America. Conservationists estimate that from 11 million to 36 million birds are captured or killed in the Mediterranean region alone every year, threatening birds like the chaffinch and the blackcap. The winter habitats of many long-distance migrants in sub-Saharan Africa have become less hospitable, with more land being cleared of vegetation to make room for agriculture.
The industrialization of farming at stopover sites has left migrating birds struggling to find food. In southern Europe, for instance, the countryside had clusters of small farms with wild spaces in between, which served as an abundant food source. Now the landscape has been homogenized into vast acreages planted with a single crop like corn and harvested more efficiently.
Reversing these alarming trends would require a diversity of conservation efforts—from protecting forests and coastlines to enforcing laws to prohibit the capture and killing of migratory birds. The use of new tracking technologies, including ever smaller geolocating tags, could help target conservation efforts, says Pete Marra, head of the Smithsonian Migratory Bird Center. On a bright afternoon in Foxton Beach in New Zealand, Jesse Conklin, wearing rubber boots and a floppy sun hat, walked out toward the salt marsh in the Manawatu River estuary, splashing through puddles of ankle-deep water left behind by the receding tide.
About 30 yards from a sand embankment, where a half dozen godwits were roosting, Conklin set up a telescope on a tripod. The Netherlands-based scientist has visited the estuary every year for the past decade. Conklin has tracked about godwits—identifiable through colored bands on their legs—that return year after year.
Over an extended period, however, the birds have advanced their departure from the estuary. Many are spending the extra days bulking up at degraded foraging sites on the Yellow Sea, arriving in Alaska at about the same time. In either case the godwits appear to be learning from experience, Conklin says, not just following a genetically programmed schedule. For hours that afternoon, Conklin trained his telescope on the godwits. Some continued to roost; others foraged nearby, dipping their bills into the mud. When a few of them waded into the water to bathe and preen, Conklin felt a familiar heightening of anticipation.
He knew that this behavior could be a precursor to a departure. The sun mellowed as the afternoon progressed, the shimmer of the water growing softer. Then, one of the godwits began making a loud, high-pitched call. Other godwits responded with similar calls.
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The conversation went on for hours. A couple of godwits flew over to join the group. Close to sunset the calling got louder, and then, all at once, the godwits took off. He adjusted his telescope to follow them—he counted 10 in all—as they made a rapid ascent over the estuary, flying out toward the ocean, first in a jumble and eventually sorting into a V-formation. Conklin watched them until they disappeared into the pale blue sky.
Read Caption. In winter the birds decamp south as far as West Africa. To make this image, Wilkes and an assistant lugged his gear steps uphill and set up near the ruins of a church about six feet from the nesting birds. Standing on the rocky ground for 28 sleepless hours, he took 1, photos. By Yudhijit Bhattacharjee.
Photographs by Stephen Wilkes. The birds are not migratory but nomadic, traveling from one lake to another, wherever food is plentiful. Wilkes shot 1, photos over 36 hours from a foot scaffolding wrapped in camouflage, capturing the endless movements of the flamingos and the marabou storks stalking them.
He chose about 30 for this image. Panoramic images capture a single day in the life of these birds. Photographer Stephen Wilkes selected a vista, set up his camera, and photographed from day to night. Wilkes then edited the photos to select the best moments and digitally blended them to compress an entire day into a seamless composite image. This story appears in the March issue of National Geographic magazine.
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From their breeding grounds in Alaska, they fly to New Zealand without a break, but on their way back they stop over at the Yellow Sea. Photograph by Jonathan Harrod, Minden Pictures. Emaciated when they arrive from Mexico and the southern United States, they fatten up to migrate on to sub-Arctic and Arctic nesting grounds.
From a blind 25 feet high, Wilkes shot 1, photos over 36 hours, using about to create this image. During the day the cranes gorge on waste grain left in fields. In the evening they return to the river in wave upon wave. While these albatrosses sit on their nests, warming and protecting their chicks, their partners soar above the ocean, swooping down to catch prey. A schedule can be downloaded HERE. This class will be held at Pittsburgh Theological Seminary N. Highland Ave. On-campus housing is available via reservation by calling or e-mailing reception pts. Programs that do not qualify for NBCC credits are clearly identified.
PPI is solely responsible for all apsects of the programs. If you do not plan to seek the certificate but are taking the class for personal enrichment, the reflection papers are not required but we strongly encourage you to read the texts to get as much as possible from the class time. Plus select two of the following that most appeal to you:. Over the past decade she has provided leadership development instruction to international State Department- and other foundation-sponsored fellows from just about every country around the world.
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