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The Great migration
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A KQED HD production.
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It starts with a distant call.
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An ancient song heard through the rising mist
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announcing the changing of the seasons.
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For thousands of years and countless generations,
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they have flown this path, arriving, then departing,
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providing a rhythmic pulse to the natural world.
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People's connection with birds and their migrations
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goes back thousands of years.
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Aristotle commented on that, and they speculated on bird migrations.
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They definitely use bird migration as a timer for their seasons.
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The robins showing up in your backyard and singing.
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The geese that show up in the fall.
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Today, scientists working in California's Central Valley
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are finding important links between bird migration and global changes,
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both natural and man-made.
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Understanding how birds use their environment and the routes they fly
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will help conservationists preserve and protect habitat.
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The information that we're getting from understanding bird migration
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is a really powerful tool for us from an applied conservation perspective.
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Some of these birds are going from one end of the globe to the other,
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and we have limited conservation funds, limited resources,
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And so it allows us really to hone in on the key sites
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that are important to different migratory animals
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and to dedicate our resources to those priority areas.
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It's long been known that migrating birds follow the wings
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of their ancestors and use the same age-old flight paths.
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Scientists call these well-traveled routes flyways.
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The whole flyway concept was developed in the 1930s
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by a guy, Frederick Lincoln, who, he was looking at band
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recoveries of waterfowl, ducks and geese, and he found that
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birds were using these predictable corridors through
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the United States. And he defined four corridors, which
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he called flyways, the Pacific, the Central and Mississippi
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flyways, and then the Atlantic flyway.
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Up to 13 different flyways have been identified
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around the world. The Pacific flyway runs from the Arctic
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circle to the tip of South America. Millions of birds from more than 300 different species
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make an annual journey up and down the Pacific Corridor, taking advantage of the best habitat
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conditions for breeding and foraging for food. The flyway in and of itself is a really interesting
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thing from an evolutionary perspective. You might wonder why birds would travel such long distances
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And it turns out it's actually more energy efficient.
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They migrate up to the north to capture the longer hours during the northern summer.
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So because it's daylight for a much longer period, they're able to forage for a longer period.
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And that helps them to be more successful in nesting and also having larger numbers of eggs that successfully hatch.
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And as those conditions change and the day length shortens,
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they migrate back down to the southern regions that are more hospitable to overwinter.
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No two species follow the same exact route.
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Some fly thousands of miles, some just a short distance,
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many crossing paths in the San Francisco Bay and the Delta.
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This is essential habitat for these long-distance travelers.
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For some birds, it's their final destination.
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For others, a crucial rest stop
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as they make the trek further south.
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You might even call the San Francisco Bay Area
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the grand central station for birds on the Pacific Flyway.
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It's really the meeting point
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for so many different bird species.
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We have your waterfowl that come down from the north.
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We have smaller species like songbird.
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We have raptors that fly through.
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And it's really just such a great mixing bowl for all of these different species.
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How birds navigate is still somewhat of a mystery.
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Some are genetically hardwired.
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Many use the sun, the stars, and landscape to guide them,
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while others are in tune with the Earth's magnetic poles.
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We don't fully understand how birds migrate
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and what might be their triggers for landing in the exact same place year to year.
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but it is true that you can put up a net in the same place year to year
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and catch the same identical bird.
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Biologist Cheryl Strong and her team from the U.S. Fish and Wildlife Service
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are banding songbirds at the Don Edwards Wildlife Refuge near Newark, California.
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So this guy's band is 0-1-7-0-1.
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Once they're banded, if they're recaptured somewhere else,
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then you get a lot of information about the movement of those birds.
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You can also get information on survival and lifespan of those birds
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and also behavior of the birds.
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Joe has a hermit thrush, which is a bird that winters here.
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It's actually really rare to know exactly where the same population of birds winters
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and also breeds, so if you can get that kind of information,
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it's really valuable to see.
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If you have a declining species, such as a songbird or even a duck,
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If you know what the threats are to that bird, either on its breeding grounds or on its wintering grounds,
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then you can better help conserve that bird.
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And there he goes.
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Biologists are now concerned with reports that the majority of migrating songbird species are suffering population declines.
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Another report by the U.S. Department of Interior indicates half of America's migrating coastal shorebird species are in decline.
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While population numbers of waterfowl vary from year to year,
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many species of ducks and geese are faring better.
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Birds face many threats along the Pacific Flyway,
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from pollution to habitat loss.
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To get a more comprehensive view of exactly where the birds go
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and what they face on their migration,
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scientists are employing sophisticated radio and satellite tracking devices.
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There's several ways you can track a migratory bird.
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One way is using satellite transmitters,
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which this is a 12-gram satellite transmitter that attaches to a bird's back.
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Powered by a solar cell, the device can send information via satellite for months, even years,
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providing scientists a way to actively follow individual birds.
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Last summer, biologists trapped and satellite-tagged long-billed curlews
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on their nesting grounds in the prairies of Montana.
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The long-billed curlew is the largest shorebird in North America.
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And it breeds in the prairies and in the Great Basin.
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And then it migrates 600 to 1,200 miles south.
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And a lot of them come to the Central Valley of California.
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And we became very interested in how important is the Central Valley for the wintering long-billed curlews.
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We found the curlews very dependent on agricultural lands, and particularly they like alfalfa.
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Biologists released the curlews in Montana and have tracked them as they've traveled down to their winter home west of Sacramento.
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We've had about 10 long-billed curlers in the valley that we've monitored over the past three years.
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And we found, interestingly, they're very sight-faithful from one year to the next.
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There's concern about the curlers because they're so dependent on man-made habitats
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much more than a lot of other species.
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Changes in habitat or climate can impact and disrupt the rhythm of migration.
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In 2009, a National Audubon Society study found that more than 150 species of migratory birds are wintering further north than they were 40 years ago.
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There's a lot of talk lately about migration phenology, which is basically the timing of migration based on what's happening in the environment.
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And the chance of that will change because of climate change.
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So the cues that birds use to migrate are changing, and it might make them migrate too soon or too late.
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And the danger is that they could arrive to the breeding ground at the wrong time.
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Migratory birds are the proverbial canary in the coal mine, a warning signal of the failing health of our ecosystems.
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Small shifts in their patterns are telling us that the rhythm of the natural world is changing.
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and those environmental changes will affect all life on this planet.
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I think it's valuable to study birds.
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They're one of the best interfaces between man and the environment.
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The real ability of birds and all the different things they do
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needs to be appreciated by the public so they want to conserve them.
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The reason I study birds is because I want to preserve the beauty of the Earth.
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- Autor/es:
- Oxford
- Subido por:
- Maria Elena D.
- Licencia:
- Reconocimiento - No comercial
- Visualizaciones:
- 167
- Fecha:
- 20 de abril de 2020 - 16:29
- Visibilidad:
- Público
- Centro:
- IES ALAMEDA DE OSUNA
- Duración:
- 10′ 18″
- Relación de aspecto:
- 1.78:1
- Resolución:
- 640x360 píxeles
- Tamaño:
- 99.30 MBytes