These birds flock in mesmerizing swarms of thousands—but why is still a mystery.
Melanie Haiken
3/27/2021
© Photograph by Nick Dunlop As a falcon streaks across the evening sky the flocks sometimes form tightly packed “ribbons”.
It’s a mesmerizing sight: Thousands of birds move in unison through the evening sky, whirling and swooping as if performing a highly synchronized ballet.
When they finally descend to their treetop roost, the beating of their iridescent wings creates such a rush of sound that the noise earned the phenomenon its unusual name: a murmuration of starlings.
The term is unique to European, or common starlings, one of the world’s most abundant—and adaptable—birds. Native to the United Kingdom as well as Europe, starlings have become invasive species throughout the U.S., Australia, New Zealand, Fiji, South Africa, and many other countries where, over centuries, they were introduced either by accident or on purpose. In the late 1890s, a group of Shakespeare enthusiasts released about a hundred European starlings into New York City’s Central Park, hoping to populate the area with every bird mentioned in the playwright’s works.
It’s a mesmerizing sight: Thousands of birds move in unison through the evening sky, whirling and swooping as if performing a highly synchronized ballet.
When they finally descend to their treetop roost, the beating of their iridescent wings creates such a rush of sound that the noise earned the phenomenon its unusual name: a murmuration of starlings.
The term is unique to European, or common starlings, one of the world’s most abundant—and adaptable—birds. Native to the United Kingdom as well as Europe, starlings have become invasive species throughout the U.S., Australia, New Zealand, Fiji, South Africa, and many other countries where, over centuries, they were introduced either by accident or on purpose. In the late 1890s, a group of Shakespeare enthusiasts released about a hundred European starlings into New York City’s Central Park, hoping to populate the area with every bird mentioned in the playwright’s works.
© Photograph by Nick Dunlop This is a starling’s point of view from inside the flock as a falcon attacks from above.
Though starlings can be a nuisance and a threat to native birds, their murmurations are breathtaking spectacles that often draw crowds to watch.
In the Northern Hemisphere, murmurations begin in fall and winter as the birds take rest stops of up to six weeks on their southern migrations. During this time, starlings may venture up to 60 miles a day from their roosting trees to feast on seeds, bugs, and larvae, then come back together to create murmurations that can last as long as 45 minutes. (Learn more about the epic journeys of migrating birds.)
© Photograph by Nick Dunlop When starlings are feeding on the ground and a falcon approaches at high speed the flocks rise quickly into the air and compress into ever changing shapes, which can intimidate a closer attack. The luckiest starlings are typically the ones in the middle.
Of course, birds moving in flocks is not a new behavior, and ornithologists have long studied it. But no other bird species flies together with the same coordination or complex patterns as European starlings, whose murmurations have been counted in numbers of up to 750,000 individuals.
What’s more, though starlings are such a ubiquitous bird, very little is known about why they murmurate.
“The bottom line is, I’ve been studying this thing for 50 years, and I still don’t know,” says ornithologist Frank Heppner, professor emeritus at the University of Rhode Island, who did some of the earliest studies of starling behavior in the 1960s.
Though starlings can be a nuisance and a threat to native birds, their murmurations are breathtaking spectacles that often draw crowds to watch.
In the Northern Hemisphere, murmurations begin in fall and winter as the birds take rest stops of up to six weeks on their southern migrations. During this time, starlings may venture up to 60 miles a day from their roosting trees to feast on seeds, bugs, and larvae, then come back together to create murmurations that can last as long as 45 minutes. (Learn more about the epic journeys of migrating birds.)
© Photograph by Nick Dunlop When starlings are feeding on the ground and a falcon approaches at high speed the flocks rise quickly into the air and compress into ever changing shapes, which can intimidate a closer attack. The luckiest starlings are typically the ones in the middle.Of course, birds moving in flocks is not a new behavior, and ornithologists have long studied it. But no other bird species flies together with the same coordination or complex patterns as European starlings, whose murmurations have been counted in numbers of up to 750,000 individuals.
What’s more, though starlings are such a ubiquitous bird, very little is known about why they murmurate.
“The bottom line is, I’ve been studying this thing for 50 years, and I still don’t know,” says ornithologist Frank Heppner, professor emeritus at the University of Rhode Island, who did some of the earliest studies of starling behavior in the 1960s.
Birds of a feather
© Photograph by Nick Dunlop This immature falcon has captured a starling and is trying to dispatch it quickly with a bite to the neck. This image also shows the starling’s fight for survival as it fights off the falcons bite with its own beak.
University of Rome physicist Andrea Cavagna has spent the past 16 years studying how starlings synchronize their movements with such precision and grace. To do so, he has created sophisticated 3-D models of the starling flocks that swirl over Piazza dei Cinquecento in Rome, where the starling population has doubled over the past decade to about a million birds.
University of Rome physicist Andrea Cavagna has spent the past 16 years studying how starlings synchronize their movements with such precision and grace. To do so, he has created sophisticated 3-D models of the starling flocks that swirl over Piazza dei Cinquecento in Rome, where the starling population has doubled over the past decade to about a million birds.
© Photograph by Nick Dunlop As a falcon approaches at high speed, the starlings turn in tight formation to avoid capture.
Together with his research partner Irene Giardina, Cavagna operates three synchronized, high-speed cameras on the roof of the Palazzo Massimo during the starlings’ winter migration.
“Every winter we have been up there in the cold and rain night after night,” says Cavagna. “It’s just us and the statues.”
Together with his research partner Irene Giardina, Cavagna operates three synchronized, high-speed cameras on the roof of the Palazzo Massimo during the starlings’ winter migration.
“Every winter we have been up there in the cold and rain night after night,” says Cavagna. “It’s just us and the statues.”
Using the video footage they capture, Cavagna and his colleagues reconstruct the positioning and velocity of a flock’s individual birds into computer models.
Their recreations reveal that starlings maintain their fluid formations via a mechanism known as scale-free behavioral correlation, in which each bird positions itself next to approximately seven other birds, coordinating its movements to create an overlapping synchronicity. (Read more about animals that swarm.)
Cavagna suggests thinking of the phenomenon as like driving on a freeway: “You interact with a fixed number of cars, maybe the one in front, the one behind, and one or two on each side, but you’re not interacting with the cars 50 meters away so you’re not distracted by them.” (It helps, he notes, that European starlings have the advantage of lateral eyesight, giving them a field of vision that extends almost all the way around their bodies.
)
© Photograph by Nick Dunlop Taken near a nightly roost site, starling flocks will often stay high in the sky when they feel threatened by an aerial predator, whether it be a falcon or a hawk. These widely changing shapes can be quite beautiful, especially when combined with dramatic evening light. Once they feel out of danger, they drop quickly to trees below.
Although each bird is interacting with its nearby neighbors, every bird’s movements affects and is affected by the entire group, allowing information to travel across the flock at a constant speed. The result is collective decision making so agile that a signal to turn, usually initiated by a bird on the outskirts, can flash through a flock of 400 birds in half a second—a speed of 90 miles per hour.
Sky dancers
The various shapes and patterns the birds create during murmurations have picturesque names: vacuole, cordon, flash expansion.
Perhaps most fascinating in appearance are the dark bands that radiate through a cloud of starlings like a moving stream, says Charlotte Hemelrijk, professor of evolutionary life sciences at the University of Groningen in the Netherlands.
These “agitation waves” look from the ground as if the starlings are drawing together more densely. But actually they are visible when the birds bank upward, tilting to show a larger area of their wing to observers below. In other words, in addition to clocking the surrounding seven birds, they’re playing follow the leader. “Our latest models show that they are copying the behavior of the nearest bird, causing the motion to roll through the flock,” Hemelrijk says. (Read why birds matter, and are worth protecting.)
Hemelrijk has also found evidence that these patterns serve to confuse predators, such as hawks and other birds of prey, and make it more difficult for them to pick off stragglers. Using sophisticated computer modeling, Hemelrijk has documented patterns of collective escape specifically tied to the movements of a predatory hawk or falcon.
Mysterious murmurations
Why European starlings circle the sky in such gigantic flocks for so long is a much more perplexing question.
The most common explanation—sometimes known as the “safer together” hypothesis—is that the swarms are a protective response against predators. But Heppner and Cavagna say that defies logic; they point out that the birds could simply return directly to their roosts, rather than amassing into huge formations and spiraling across the sky.
“You would think they would want to minimize flying time, but instead they go through this spectacular display for half an hour to 45 minutes, burning up energy at a ferocious rate,” Heppner says.
“And meanwhile they’re actually attracting predators. it’s like they’re saying, We’re here, we’re here. You have to ask yourself, how did a mechanism like this evolve?”
Another possible explanation, sometimes called the “warmer together” theory, suggests that murmurations function to advertise a roosting site, attracting greater numbers of birds to the flock to conserve body heat.
In an attempt to solve the mystery, researchers from the University of Gloucester and the Royal Society of Biology compiled data from more than 3,000 murmurations, data that volunteers in 23 countries collected in 2014 and 2015. The results, published in 2017, showed no correlation between temperature and murmuration size, leaving little support for the warmth hypothesis.
The study also reported the presence of a hawk, falcon, or other bird of prey in just under a third of the murmurations, offering some support for the predation theory—yet leaving unexplained why the birds join together in such lengthy performances.
An act of pure beauty?
On one characteristic of the starlings, though, researchers are in agreement: the birds are remarkably intelligent. When Heppner kept starlings in captivity for his research, he says, “they were so good at picking the locks on their cages, we had to put padlocks on them.”
With the birds’ brain power in mind, is it possible that murmurations are simply their conscious expression of a sheer joy of movement? (Read more about animals that “dance.”)
“In the absence of a predator, I do think it’s possible to see these displays as a sort of dancing,” says the University of Groningen’s Hemelrijk.
“We don’t want to attribute too much intention, but they’re certainly very excited. They do this for a very long time sometimes,” she says, “when they could just go to sleep.”
Although each bird is interacting with its nearby neighbors, every bird’s movements affects and is affected by the entire group, allowing information to travel across the flock at a constant speed. The result is collective decision making so agile that a signal to turn, usually initiated by a bird on the outskirts, can flash through a flock of 400 birds in half a second—a speed of 90 miles per hour.
Sky dancers
The various shapes and patterns the birds create during murmurations have picturesque names: vacuole, cordon, flash expansion.
Perhaps most fascinating in appearance are the dark bands that radiate through a cloud of starlings like a moving stream, says Charlotte Hemelrijk, professor of evolutionary life sciences at the University of Groningen in the Netherlands.
These “agitation waves” look from the ground as if the starlings are drawing together more densely. But actually they are visible when the birds bank upward, tilting to show a larger area of their wing to observers below. In other words, in addition to clocking the surrounding seven birds, they’re playing follow the leader. “Our latest models show that they are copying the behavior of the nearest bird, causing the motion to roll through the flock,” Hemelrijk says. (Read why birds matter, and are worth protecting.)
Hemelrijk has also found evidence that these patterns serve to confuse predators, such as hawks and other birds of prey, and make it more difficult for them to pick off stragglers. Using sophisticated computer modeling, Hemelrijk has documented patterns of collective escape specifically tied to the movements of a predatory hawk or falcon.
Mysterious murmurations
Why European starlings circle the sky in such gigantic flocks for so long is a much more perplexing question.
The most common explanation—sometimes known as the “safer together” hypothesis—is that the swarms are a protective response against predators. But Heppner and Cavagna say that defies logic; they point out that the birds could simply return directly to their roosts, rather than amassing into huge formations and spiraling across the sky.
“You would think they would want to minimize flying time, but instead they go through this spectacular display for half an hour to 45 minutes, burning up energy at a ferocious rate,” Heppner says.
“And meanwhile they’re actually attracting predators. it’s like they’re saying, We’re here, we’re here. You have to ask yourself, how did a mechanism like this evolve?”
Another possible explanation, sometimes called the “warmer together” theory, suggests that murmurations function to advertise a roosting site, attracting greater numbers of birds to the flock to conserve body heat.
In an attempt to solve the mystery, researchers from the University of Gloucester and the Royal Society of Biology compiled data from more than 3,000 murmurations, data that volunteers in 23 countries collected in 2014 and 2015. The results, published in 2017, showed no correlation between temperature and murmuration size, leaving little support for the warmth hypothesis.
The study also reported the presence of a hawk, falcon, or other bird of prey in just under a third of the murmurations, offering some support for the predation theory—yet leaving unexplained why the birds join together in such lengthy performances.
An act of pure beauty?
On one characteristic of the starlings, though, researchers are in agreement: the birds are remarkably intelligent. When Heppner kept starlings in captivity for his research, he says, “they were so good at picking the locks on their cages, we had to put padlocks on them.”
With the birds’ brain power in mind, is it possible that murmurations are simply their conscious expression of a sheer joy of movement? (Read more about animals that “dance.”)
“In the absence of a predator, I do think it’s possible to see these displays as a sort of dancing,” says the University of Groningen’s Hemelrijk.
“We don’t want to attribute too much intention, but they’re certainly very excited. They do this for a very long time sometimes,” she says, “when they could just go to sleep.”
 - European utilities are offering a slew of offshore wind farms, eager to cash in on high valuations as investors hungry for stable returns increasingly flock to the sector, people close to the matter said. Demand for such assets has surged as environmentally-conscious investors and industries such as oil and gas seek green power in order to meet goals to achieve net zero emissions in line with the 2015 Paris climate agreement. Denmark's Orsted, Switzerland's Axpo, Germany's EnBW and Sweden's Vattenfall are all marketing offshore wind assets that are either at project stage or completed, four people familiar with the matter said. Specialised infrastructure investors including FSI, Equitix, PGGM, APG, MIRA, Omers, Glennmont, IFM, CDPQ, Omers, Ardian, as well as oil majors are being targeted in the various auctions, the people said. "There is a massive influx of capital and it is driven by pension funds and insurance companies," said Mortimer Menzel, partner at Augusta & Co, which specialises in renewables deal advisory. "It drives utilities to recycle their assets because, quite frankly, they're getting a higher price today than they did last year and the window won't be open forever," he said, adding there was a huge scarcity of assets at the moment. For utilities, selling stakes in farms or projects is part of their strategy to get these assets, which usually require spending of at last 1 billion euros ($1.2 billion) apiece, off the ground. Orsted, the world's No.1 developer of offshore wind farms, is in talks to sell part of its 900 megawatt (MW) Borkum Riffgrund 3 project to an investor in a deal worth up to 2 billion euros, the people said. Glennmont Partners has been seen in pole position as a buyer but talks have not yet been finalised, they added. Meantime, Axpo has already kicked off the sale of its 24.1% stake in the 400 MW Global Tech I farm, located about 100 kms (62 miles) off Germany's North Sea coast, the people said. Axpo has already approached potential buyers including owners of adjacent wind parks like APG and Macquarie as well as EnBW, which may be able to reap synergies from a potential combination, one of the people added. Video: Deutsche Post DHL CEO 'very optimistic' about company's sustainable fuel target (CNBC) Pause Current Time 0:33 / Duration 2:54 Unmute 0 LO CaptionsFullscreen Deutsche Post DHL CEO 'very optimistic' about company's sustainable fuel target Click to expand Other investors in Global Tech I, which entered operation in 2015 and produces enough electricity to supply about 450,000 households, have also signalled their willingness to exit, and a buyer could get a majority in the business, the people said. Orsted, Glennmont and Axpo declined to comment. GRAPHIC: European offshore wind investments - https://graphics.reuters.com/ENERGY-EUROPE/dgkpleqbqvb/chart.png Valuations for renewables assets have soared, with the global FTSE cleantech index more than doubling over the past year on demand from investors, including oil majors who are under increasing pressure to find new sources of profit. "The historical gap between returns from oil & gas upstream and renewables has significantly narrowed," said Maria Garijo, co-head of EMEA power investment banking at Bank of America. "However, big oil is likely to prefer to tread carefully when investing in renewables in the near term as they continue to adapt their financial frameworks and fulfil their dividend commitments." Despite the pandemic, 2020 has been a record year for offshore wind financing in Europe, climbing to 26.3 billion euros last year, according to industry body WindEurope. EnBW is expected to mandate advisors for the sale of a stake in its 900 MW He Dreiht project, to be located about 110 kms west of Heligoland in the North Sea, in autumn, potentially launching an auction later this year or in 2022, the people said. The company said that while for now its operating focus regarding He Dreiht remained developing the project until an investment decision has been taken, funding partnerships are part of its renewables business model. In May, Vattenfall is expected to send out information packages in the planned sale of a stake in its Dutch 1.5 GW Hollandse Kust Zuid wind park, which is slated to go online in 2023, the people said. Vattenfall, which communicated the sales plans last year, declined to comment on the timeline of the deal, adding that RBC Capital Markets is helping it to find an investor. "We call this asset ownership flexibility," it said. In a sign of how big interest in renewables assets currently is, Spain's Iberdrola is getting unsolicited bids for some of its wind farms, including Germany's 476 MW Baltic Eagle project, the people said. But while the company, which in 2019 sold a stake in its East Anglia One wind park, is looking for partners to finance the construction of Baltic Eagle, it is aiming to retain full ownership, they added. Iberdrola declined to comment. ($1 = 0.8472 euros) (Additional reporting by Isla Binnie and Jacob Gronholt-Pedersen; Editing by Emelia Sithole-Matarise)){kind=link}
