The sky is empty.
Bird numbers in the United States and Canada have decreased by 29 percent since 1970, scientists said Thursday. There are now 2.9 billion fewer birds hiding than 50 years ago.
The analysis published in the journal Science is the most comprehensive and ambitious experience that cannot yet learn what is happening to bird populations. The results shocked researchers and environmental organizations.
In a statement Thursday, David Yarnold, president and CEO of the National Audubon Society, called the results "a complete crisis."
There are probably many reasons, the most important of which include habitat loss and increased use of pesticides. The Silent Spring, Rachel Carson's prophetic book of 1962 on the damage caused by pesticides, takes its title from the unnaturally quiet settlement of a world that lost its birds:
"In the mornings that once sunk at dawn . there were no sounds from slaves, cats, pigeons, jays, backpacks and many other bird voices. "
Kevin Gaston, a conservation biologist at the University of Exeter, said the new findings signal something more about the work:" This is the loss of nature. "
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Ordinary bird species are vital to ecosystems, control pests, pollinate flowers, spread seeds and regenerate forests. When these birds disappear, their former habitats are often not the same.
"The decline in your common sparrow or other small brown bird may not receive the same attention as historic losses of bald eagles or sand faucets, but they will have much more impact," says Hilary Young, a conservation biologist at UCLA. Santa Barbara, which did not participate in the new research.
A team of researchers from universities, government agencies, and non-governmental organizations collaborated on a new study combining old and new bird counting methods.
For decades, professional ornithologists have been assisted by an army of dedicated birdwatchers who submit their observations to databases and help carry out surveys of bird populations each year.
In a new study, researchers turned to these studies to estimate populations of 529 species between 2006 and 2015.
These estimates include 76 percent of all bird species in the US and Canada, but represent almost the entire population. of birds. (Species for which there was insufficient data to make firm estimates are found only in small numbers.)
The researchers then used bird monitoring records to estimate the population of each species after 1970, most an early year for which there is solid data.
"This approach of combining population estimates across species and seeking an overall trend is truly unprecedented," says Scott Los, a conservation biologist at Oklahoma State University who was part of the new study.
As some species grow, found by researchers, the majority declines – often by huge numbers.
"We were amazed at the result – it was just staggering," says Kenneth W. Rosenberg, a Cornell University Conservation Scientist and American Bird Protection and lead author of the new study.
"We are afraid that not only these highly endangered birds will be listed as endangered," he said. "It's beyond the board."
Meteorological radar offers another way to track bird populations. Dr. Rosenberg and his colleagues counted birds recorded on radars at 143 stations in the United States from 2007 to 2018. They focused on scanning in the spring when birds migrated in large numbers.
The team measures a 14 percent drop over this period
"If we have two datasets showing the same thing, it's home running," says Nicole Michel, senior quantitative ecologist at the Audubon Society, who was not involved in the study.
Among the hardest hit groups were wars, with a population declining by 617 million. There are 440 million fewer black birds than there ever were .
p. Rosenberg said he was surprised by how wide the population was declining. Even cattle, a species that has become a rapidly breeding pest since its introduction in the United States in 1890, has decreased by 83 million birds, a 49% decline.
Europe is experiencing similar bird loss, also among common species, said Dr Gaston of the University of Exeter. "The numbers are broadly comparable," he said.
The new study is not intended to determine why birds disappear, but the results – like earlier studies – indicate some likely culprits, says Dr. Rosenberg.
Grass species have suffered the largest decline so far, ie. lost 717 million birds.
"Every field that is plowed, and every wetland that is drained, you lose birds in that area," says Dr. Rosenberg.
In addition to habitat loss, pesticides may have levied tax. A study published last week, for example, found that pesticides called neonicotinoids make it difficult for birds to gain the weight needed for migration, slowing their travel.
The researchers found some positive signs. Bald eagles, for example, are flourishing, and falcon populations have increased by 33 percent.
For the most part, there is a small mystery as to how these happy exceptions came to be. Many restorative bird species have been virtually wiped out over the last century by pesticides, hunting and other pressures. Conservation measures allowed them to rebound.
"In those cases, we knew the reasons and acted on it," Dr. Rosenberg said. "They are models of success."
But some thriving populations are harder to explain.
Vireo-like small birds called vireoses grow 89 million more birds than in 1970 – a jump of 53 percent. Yet cavemen, who share the same habitat as Viraeus, have fallen by 37 percent.
"I have no idea why the Vireos are doing well," says Dr. Rosenberg. "I'd be glad to do a study on Vireos and find out what their secret is."
One scale of bird decline meant that stopping it would require tremendous effort, said Dr. Young of the University of California, Santa Barbara. Habitats should be protected, chemicals should be restricted, buildings should be remodeled. "We overdo it with the world, so it affects everything," she said.
The Audubon Society calls for the protection of bird-rich habitats, such as the Great Lakes and the Colorado River Basin, and for the maintenance of
the Society and other bird advocacy groups also offer things that humans can do. They insist on keeping the cats inside so they don't kill smaller birds. A large number of birds die each year after flying in windows; there are ways to make the glass more visible to them.
For some birders, the findings of the study confirm a fearsome judgment.
Beverly Gyllenhaal, 62, a retired cookbook author, and her husband Anders have spotted 256 species in parks in the eastern United States. But when he visits his mother in North Carolina in recent years, it seems like there are not as many birds as he can remember from his childhood there.
And when she talks to people in the United States about her bird trips, many people say the same thing. "Often people will tell you, 'It's not like it used to be,'" she said.
The expected losses terrified her. "If the cardinals and blue jays and sparrows are not doing well," she said, "it's really scary."