The ancestors of modern birds may have survived the asteroid strike that wiped out the rest of their kin by living on the forest floor.
The new theory, based on studying fossilised plants and ornithological data, helps explain how birds came to dominate the planet.
The asteroid impact 66 million years ago laid waste to the world’s forests.
Ground-dwelling bird ancestors managed to survive, eventually taking to the trees when the flora recovered.
“It seems clear that being a relatively small-bodied bird capable of surviving in a tree-less world would have conferred a major survival advantage in the aftermath of the asteroid strike,” said Dr Daniel Field of the Milner Centre for Evolution at the University of Bath.
We already know that the early ancestors of modern birds were probably capable of flight, and relatively small in size.
Scientists have now pieced together their ecology to better understand how these partridge-like bird ancestors managed to avoid destruction in a particularly bleak moment in the Earth’s history.
“Teasing these stories from the rock record is a challenge when the action took place over 66 million years ago, over a relatively short period of time,” said Dr Field, who led a team of UK, US and Swedish researchers.
The plant fossil record shows that the asteroid caused global deforestation and extinction of most flowering plants, destroying the habitats of tree-dwelling animals.
Birds didn’t move back into the trees again until the forests recovered thousands of years later.
“The recovery of canopy-forming trees such as palms and pines happened much later, which coincides with the evolution and explosion of diversity of tree-dwelling birds,” said Dr Antoine Bercovici from Smithsonian Institution.
The researchers found that once the forests had recovered, birds began to adapt to living in trees, acquiring shorter legs than their ground-dwelling ancestors and various specialisations for perching on branches.
They eventually diversified into ostriches and their relatives, chickens and their relatives, and ducks and their relatives.
“Perhaps the best modern analogue for one of the surviving birds lineages are modern tinamous – this is a modern group of flying relatives of ostriches: they are relatively small bodied, and live on the ground,” said Dr Field.
Today’s “amazing living bird diversity can be traced to these ancient survivors”, he added.
The research is published in the journal Current Biology.
Songbirds known as Japanese tits communicate using human-like rules for language and can mentally picture what they’re talking about, research suggests.
by Brandon Keim
Hear a word, particularly an important one — like “snake!” — and an image appears in your mind. Now scientists are finding that this basic property of human language is shared by certain birds and, perhaps, many other creatures.
In a series of clever tests, a researcher has found that birds called Japanese tits not only chirp out a distinctive warning for snakes, but also appear to imagine a snake when they hear that cry. This glimpse into the mind’s eye of a bird hints at just how widespread this ostensibly human-like capacity may be.
“Animal communication has been considered very different from human speech,” says Toshitaka Suzuki, an ethologist at Japan’s Kyoto University. “My results suggest that birds and humans may share similar cognitive abilities for communication.”
Perhaps this went unappreciated for so long, says Suzuki, simply because “we have not yet found a way to look at the animals’ minds.”
Over the last several years, Suzuki conducted a series of experiments deciphering the vocalizations of Japanese tits — or Parus minor, whose family includes such everyday birds as chickadees and titmice — and describing their possession of syntax, or the ability to produce new meanings by combining words in various orders. (“Open the door,” for example, versus “the open door.”)
Syntax has long been considered unique to human language, and language in turn is often thought to set humans apart from other animals. Yet Suzuki found it not in a bird typically celebrated for intelligence, like crows or parrots, but in humble P. minor.
Once he realized that birds are using their own form of language, Suzuki wondered: what happens in their minds when they talk? Might words evoke corresponding images, as happens for us?
Suzuki tested that proposition by broadcasting recordings of P. minor’s snake-specific alarm call from a tree-mounted speaker. Then he analyzed the birds’ responses to a stick that he’d hung along the trunk and could manipulate to mimic a climbing snake.
If the call elicited a mental image, Suzuki figured the birds would pay extra-close attention to the snake-like stick. Indeed they did, he recently reported in the journal Proceedings of the National Academy of Sciences.
In contrast, when Suzuki broadcast a call used by tits to convey a general, non-specific alarm, the birds didn’t pay much notice to the stick. And when he set the stick swinging from side to side in a decidedly non-snakelike manner, the birds ignored it.
“Simply hearing these calls causes tits to become more visually perceptive to objects resembling snakes,” he writes in PNAS. “Before detecting a real snake, tits retrieve its visual image from snake-specific alarm calls and use this to search out snakes.”
Rob Magrath, a behavioral ecologist at Australia National University who specializes in bird communication, thinks Suki’s interpretation is consistent with the results. He also calls the work “truly delightful.”
“I love the way that Suzuki employs simple experiments, literally using sticks and string, to test ideas,” Magrath says. Similarly impressed is ecologist Christine Sheppard of the American Bird Conservancy. “It’s incredibly challenging to devise an experiment that would allow you to answer this question,” she says. “It’s really neat.”
MINDS OF THEIR OWN
Sheppard says it makes evolutionary sense for animals to possess a ‘mind’s eye’ that works in tandem with their communications: It allows individuals to respond more quickly to threats. Suzuki agrees, and believes it’s likely found not only in P. minor and their close relatives, but in many other birds and across the animal kingdom.
“Many other animals produce specific calls when finding specific types of food or predators,” he says. He hopes researchers will use his methodology to peek into the mind’s eyes of other animals.
For Sheppard, the findings also speak to how people think about birds: not just as pretty or interesting or ecologically important, but as fellow beings with rich minds of their own.
“When I was in school, people still thought that birds were little automata. Now “bird brain” is becoming a compliment,” she says.
“I think this kind of insight helps people see birds as living, breathing creatures with whom we share the planet,” she says.
The birds seem to buffer humans from West Nile virus, according to a new study, especially in cities with more patches of old-growth forest.
by Rusell McLendon
The northern cardinal is one of North America’s most familiar songbirds. From the scarlet feathers and pointed crest of males to the rich, rhythmic songs of both sexes, it’s an unmistakable icon of countless American forests, parks and backyards.
And as a new study demonstrates, northern cardinals are much more than just scenery and a soundtrack. As part of eastern North America’s native biodiversity, they can also play a key role in keeping ecosystems — including humans — healthy.
That’s according to new research from Atlanta, where a team of scientists wanted to figure out why more people don’t get sick with West Nile virus (WNV). The mosquito-borne virus is zoonotic, meaning it can be spread between humans and other animals by a “bridge vector,” a role played by Culex mosquitoes for WNV.
Since WNV was introduced to the U.S. in 1999, it has become the country’s most common zoonotic disease carried by mosquitoes, causing more than 780,000 infections and 1,700 deaths. But for some reason, the virus sickens people in some areas more than others. It’s abundant in both Georgia and Illinois, for example, showing up in nearly 30 percent of birds tested in Atlanta, compared with 18.5 percent in Chicago. Yet only 330 human cases have been reported throughout Georgia since 2001, while Illinois has seen 2,088 human cases since 2002.
“When West Nile virus first arrived in the United States, we expected more transmission to humans in the South, because the South has a longer transmission season and the Culex mosquitos are common,” says senior author Uriel Kitron, chair of environmental sciences at Emory University, in a statement. “But even though evidence shows high rates of the virus circulating in local bird populations, there is little West Nile virus in humans in Atlanta and the Southeast in general.”
The reason for that difference has remained a mystery for years, prompting a three-year study by a team of scientists from Emory, the University of Georgia, the Georgia Department of Transportation and Texas A & M University. They collected mosquitoes and birds from various sites across Atlanta, tested them for WNV, and analyzed DNA from their blood meals to learn which birds they’d been biting.
“We found that the mosquitoes feed on American robins a lot from May to mid-July,” says lead author Rebecca Levine, a former Emory Ph.D. student now working at the U.S. Centers for Disease Control and Prevention (CDC). “But for some unknown reason, in mid-July, during the critical time when the West Nile virus infection rate in mosquitos starts going up, they switch to feeding primarily on cardinals.”
Previous research has shown American robins act as “super spreaders” of WNV in some cities like Chicago, Levine adds. Something about their blood creates a favorable environment for WNV, so the virus amplifies wildly once a robin is infected, meaning the birds can more efficiently pass it to new mosquitoes when bitten.
But cardinals have the opposite effect. Their blood is like an abyss for WNV, leading the researchers to describe the birds as “super suppressors” of the virus.
“You can think of the cardinals like a ‘sink,’ and West Nile virus like water draining out of that sink,” Levine says. “The cardinals are absorbing the transmission of the virus and not usually passing it on.” Cardinals seem to be the top suppressors of WNV, the study found, but similar effects are seen in birds from the mimid family — namely mockingbirds, brown thrashers and gray catbirds, all of which are common in Atlanta.
Humans use a unique call to request help from honeyguide birds, and the birds also ‘actively recruit’ human partners. This is two-way teamwork, scientists say, a rarity between people and wildlife.
By Russell McLendon
When a human makes that sound in Mozambique’s Niassa National Reserve, a wild bird species instinctively knows what to do. The greater honeyguide responds by leading the human to a wild beehive, where both can feast on honey and wax. The bird does this without any training from people, or even from its own parents.
This unique relationship pre-dates any recorded history, and likely evolved over hundreds of thousands of years. It’s a win-win, since the birds help humans find honey, and the humans (who can subdue a beehive more easily than the 1.7-ounce birds can) leave behind beeswax as payment for their avian informants.
While this ancient partnership is well-known to science, a new study, published July 22 in the journal Science, reveals incredible details about how deep the connection has become. Honeyguides “actively recruit appropriate human partners,” the study’s authors explain, using a special call to attract people’s attention. Once that works, they fly from tree to tree to indicate the direction of a beehive.
Not only do honeyguides use calls to seek human partners, but humans also use specialized calls to summon the birds. Honeyguides attach specific meaning to “brrr-hm,” the authors say, a rare case of communication and teamwork between humans and wild animals. We’ve trained lots of domesticated animals to work with us, but for wildlife to do so voluntarily — and instinctively — is pretty wild.
Here’s an example of what the “brrr-hm” call sounds like:
“What’s remarkable about the honeyguide-human relationship is that it involves free-living wild animals whose interactions with humans have probably evolved through natural selection, probably over the course of hundreds of thousands of years,” says lead author Claire Spottiswoode, a zoologist at the University of Cambridge.
“[W]e’ve long known that people can increase their rate of finding bees’ nests by collaborating with honeyguides, sometimes following them for over a kilometer,” Spottiswoode explains in a statement. “Keith and Colleen Begg, who do wonderful conservation work in northern Mozambique, alerted me to the Yao people’s traditional practice of using a distinctive call which they believe helps them to recruit honeyguides. This was instantly intriguing — could these calls really be a mode of communication between humans and a wild animal?”
To answer that question, Spottiswoode went to Niassa National Reserve, a vast wildlife refuge larger than Switzerland. With the help of honey hunters from the local Yao community, she tested whether the birds can distinguish “brrr-hm” — a sound passed down from generation to generation of Yao hunters — from other human vocalizations, and if they know to respond accordingly.
She made audio recordings of the call, along with two “control” sounds — arbitrary words spoken by the Yao hunters, and the calls of another bird species. When she played all three recordings in the wild, the difference was clear: Honeyguides proved much more likely to answer the “brrr-hm” call than either of the other sounds.
“The traditional ‘brrr-hm’ call increased the probability of being guided by a honeyguide from 33 percent to 66 percent, and the overall probability of being shown a bees’ nest from 16 percent to 54 percent compared to the control sounds,” Spottiswoode says. “In other words, the ‘brrr-hm’ call more than tripled the chances of a successful interaction, yielding honey for the humans and wax for the bird.”
The researchers released this video, which includes footage from their experiments
This is known as mutualism, and while lots of animals have evolved mutualistic relationships, it’s very rare between humans and wildlife. People also recruit honeyguides in other parts of Africa, the study’s authors note, using different sounds like the melodious whistle of Hadza honey hunters in Tanzania. But aside from that, the researchers say the only comparable example involves wild dolphins who chase schools of mullet into anglers’ nets, catching more fish for themselves in the process.
“It would be fascinating to know whether dolphins respond to special calls made by fishermen,” Spottiswoode says.
The researchers also say they’d like to study if honeyguides learned “language-like variation in human signals” across Africa, helping the birds identify good partners among the local human population. But however it began, we know the skill is now instinct, requiring no training from people. And since honeyguides reproduce like cuckoos — laying eggs in other species’ nests, thus tricking them into raising honeyguide chicks — we know they don’t learn it from their parents, either.
This human-honeyguide relationship isn’t just fascinating; it’s also threatened, fading away in many places along with other ancient cultural practices. By shedding new light on it, Spottiswoode hopes her research can also help preserve it.