VOA慢速英语--科技为科学家提供了更好的跟踪鸟类的方法（在线收听）

Technology Gives Scientists Better Ways to Follow Birds

A well-fed songbird jumps around in grass near Washington, D.C. On its back it carries a very small, lightweight electronic device called a tag. The bird, a robin, sees an insect nearby. The bird attacks fast --- and wins a meal.

Ecology scientist Emily Williams watches from behind a bush. On this clear spring day, she says, "Now I'm watching to see whether he's found a mate," The bird has moved to a nearby tree where there is another robin.

When the bird leaves, the device it carries will send data about its position to a special satellite, then back to Williams' computer.

The Georgetown University ecologist will be able to track the animal's movement.

The satellite involved is Argos. The goal of the project is to learn why some American robins travel long distances on a usual basis, or migrate, but others do not. The new tracking system promises to give more exact information about the places robins mate and raise their young and where they spend the winter. That will help scientists understand the importance of "genetics versus the environment in shaping why birds migrate," Williams said.

Researchers have been attaching tracking tags on birds and animals for many years. But, the International Space Station and the Argos satellite now provide new ways to receive the information sent by the tags. The new system permits scientists to watch songbird movements from afar in much greater detail than before.

"We're in a sort of golden age for bird research," said Adriaan Dokter, an ecologist at Cornell University, adding that the technology is improving as the tags are made smaller and smaller.

"We can satellite-track a robin with smaller and smaller chips. Ten years ago, that was unthinkable," said the scientist, who is not involved in Williams' study.

The device that the robin wears can report its immediate place on Earth, within about 10 meters.

A second new device, for only the heaviest robins, provides more information about the bird's movements; future versions may also measure the humidity and barometric pressure of the space the bird occupies.

The devices are known as ICARUS tags.

Martin Wikelski is director of the Max Planck Institute of Animal Behavior. His scientific team is working to improve the ICARUS technology. He hopes that more and better devices could help develop what he called, "an 'Internet of animals' - a collection of sensors around the world giving us a better picture of the movement of life on the planet."

The first bird of spring

The American robin is a well-known songbird in North America. Its song announces the coming of spring. Yet its migratory life remains mysterious.

Ken Rosenberg is a conservation scientist at Cornell University. He says it is surprising "how little we know about some of the most common songbirds."

An earlier study Williams worked on showed some robins are long-distance migrants – from Alaska to Texas - while others, for unknown reasons, stay in a single place most of the year.

Williams hopes more detailed data from satellite tags will answer her questions. She is working with partners who are tagging robins in Alaska, Indiana and Florida for a three-year study.

Catching a robin

Williams has placed nets between tall poles in her yard. When a robin flies into the net, she carefully removes the bird. She measures the bird's body and pulls out a single feather to check on its overall health.

Then she weighs the bird. This one is about 80 grams, just big enough to wear the satellite tag. The technology has only recently become small and light enough to use with small songbirds. Tracking devices have to weigh less than five percent of the animal's weight for it to fly normally.

30 percent drop in bird population

Cornell scientist Rosenberg co-wrote a study in 2019 that showed North America's population of wild birds has dropped by almost three billion, or 30 percent, since 1970.

Ben Freeman is a life scientist at the Biodiversity Research Centre at the University of British Columbia. He says the tracking will help show why the bird population numbers are going down. Better information about migration paths "will help us look in the right places."

Words in This Story

versus – prep. used to indicate two different things, choices, etc., that are being compared or considered

migrate – v. to move from one area to another at different times of the year

track – v. to follow or watch the path of (something)

tag – n. a small piece of cloth, paper, metal, or an electronic device that is attached to something

humidity – n. moisture in the air

barometer – n. an instrument that is used to measure air pressure and predict changes in the weather

feather – n. one of the light growths that make up the outer covering of the body of a bird