Tag Archives: crow

Clever crows can grasp the concept of ‘zero’

Crows are some of the most intelligent creatures in the world, not just of the bird kingdom. They use tools, which they’ve crafted themselves, to reach otherwise inaccessible food; remember people’s faces and even hold grudges; understand water displacement better than some human children; and solve highly complex puzzles involving intricate steps. Bearing all of this in mind, it’s no surprise to learn that scientists have found that crows can also understand the concept of zero.

Credit: Pixabay.

Zero — the abstraction for nothingness — is a pretty challenging concept to grasp. Studies have shown that humans generally don’t fully grasp it until kindergarten, and civilization required quite the thought leap in order to incorporate the concept into mathematics — it didn’t become incorporated into our number system until the fifth or sixth century A.D in India.

Despite being skilled mathematicians in their own right, the Mayans and Romans never used the concept of zero as a mathematical abstraction, though, of course, they understood the concept of nothing or having nothing. 

Although it might sound trivial today, the concept of “nothing” was revolutionary for numbers, and went on to change mathematics from the ground up. It underpinned the development of calculus, which is strongly entrenched across modern fields of science.

“The Indian [or numerical] zero, widely seen as one of the greatest innovations in human history, is the cornerstone of modern mathematics and physics, plus the spin-off technology,” according to Peter Gobets, secretary of the ZerOrigIndia Foundation.

Besides humans, scientists previously found that rhesus macaques and even honeybees can understand zero as an abstract concept. The huge leap between macaques and honeybees suggests that many other animals may also possess this ability.

In a new study, researchers at the Institute of Neurobiology at the University of Tübingen in Germany made their own investigation by studying crows, promising candidates considering their proven track record of completing brainy tasks.

The team of researchers led by Andreas Nieder, a professor of animal physiology, had a lot of experience working with carrion crows having previously shown that the birds can count and encode numbers in specific neurons in their brain. The crows had to interact with a computer monitor in front of them where one to four black dots appeared on a gray screen. This image was followed by a new frame that contained either the same number of dots or a different number of dots.

The trained crows had to peck the screen or move their heads if the number of dots coincided, and had to remain perfectly still if the dots didn’t match. Since the crows selected the correct pairs 75% of the time, the researchers concluded that crows could count, despite some errors that most frequently occurred when the frames had a similar number of dots (i.e. the crows mistook a three-dot subsequent screen for a four-dot screen). Scientists refer to this phenomenon as the numerical distance effect, which has been observed before in monkeys and humans.

Now, six years later, the researchers repeated the experiment with an additional blank screen, representing no dots or “zero”. Just like other countable numbers, the crows showed that they could discriminate zero. Notably, the numerical distance effect was preserved even in situations involving the blank screen. For instance, the crows were more likely to mistakenly peck the display when a screen with a single dot or two dots was shown than when three or four dots were shown.

“This is an indication that they treat the empty set, not just as ‘nothing’ versus ‘something,’ but really as a numerical quantity,” Nieder told Live Science.

Nieder and colleagues worked with two trained carrion crows that had glass-coated wires implanted into their brains in order to monitor their brain activity. The implants were made in a region of the brain known as the pallium, found close to the back of the brain. The pallium is involved in high-level cognitive functions.

This way, the researchers recorded patterns of brain activity that reflected how the crows perceived numerical values in relation to one another.

“They are inherently representing this ordinality aspect of numbers, this ordering along a number line, so that after one comes two and after two comes three, and so on,” Nieder added.

What’s more, the new study showed, the crows’ different neurons lit up in response to the blank screen, which became less and less active as more dots popped on the screen. The further away from zero, the less specific brain activity the researchers recorded.

Corroborating data on the birds’ behavior with their brain activity, the researchers in Germany concluded that crows must be able to grasp the concept of zero. That’s remarkable since the lineage of mammals like humans and birds split many millions of years ago, well before the extinction of the dinosaurs, yet the two seem to still share overlapping cognitive abilities. This suggests that evolution independently equipped mammals and birds with high-level cognitive functions.

The findings appeared in The Journal of Neuroscience.

Jackdaws can distinguish ‘dangerous’ people from friendly ones

The results of a new study suggest that jackdaws, a relative of the crow, can learn which humans are ‘safe’ and which are ‘dangerous’.

Image credits John Haslam / Flickr.

The birds use cues from their fellows to learn which humans are to be seen as a threat, reports a team from the University of Exeter. Furthermore, they are able to recognize individual people and react to them based on their perceived threat level.

Cawing murder

“One of the big challenges for a lot of animals is how to live alongside humans,” said lead author Victoria Lee, a Ph.D. researcher at the Centre for Ecology and Conservation on Exeter’s Penryn Campus in Cornwall.

“People can provide some benefits, such as the food at bird feeders, but in some cases humans are also a threat.

The crow family of birds, to which the jackdaw (Coloeus monedula) belongs, is known for its intelligence. Crows can make and use tools, recognize our faces, and are quite good with puzzles. According to the Cornell Lab of Ornithology’s allaboutbirds, “crows have more than 20 calls,” with the most common being “a harsh caw” which can take many different meanings depending on its quality or length.

Jackdaws themselves resemble crows but have distinctive gray neck plumage and irises. There are four subspecies of Jackdaw. All are loud, boisterous and live in relatively small groups but are very social. They’re also able to learn from the group which humans to hide from, the findings suggest.

Lee’s team worked on three sites in Cornwall (34 Jackdaw nest boxes) during the 2017 breeding season. One of the researchers put on a mask and came close to their nests while the rest of the team played recordings of either ‘scold calls’ or ‘contact calls’ (the latter of which suggests no threat).

“Scold calls are antipredator vocalizations given by jackdaws to recruit others to mob a predator,” the paper notes.

The second phase of the experiment had the researcher (with the mask) return to the nests after some time, and see if there was a difference in their behavior. There was. The birds that had heard scold calls returned more quickly to their nests than the others.

Jackdaws that were played scold calls when first seeing the masked researcher returned to their nest quicker (in 53% of the initial time), while birds that heard contact calls took relatively longer (63% of the initial time) on average. The team notes that the calls did not appear to influence how long birds took to enter their nest box, or how long they spent inside, only how quickly they returned to them.

“Being able to discriminate between dangerous and harmless people is likely to be beneficial, and in this case we see jackdaws can learn to identify dangerous people without having had a bad experience themselves,” Lee explains.

The paper “Social learning about dangerous people by wild jackdaws” has been published in the journal Royal Society Open Science.

Where crows go in the winter — and other stories about migration

When winter comes, not all crows react the same. Some stay right where they are, toughing out the frigid days as they best can. Others choose to move to warmer areas, returning only when the cold has faded away. This is called a partial migration.

Image credits: M. Jones.

Animal migration is a spectacular behavior that has fascinated humans since times immemorial. But most people aren’t aware that the most common form of migration in animals is actually partial migration — where just a fraction of the individuals migrate, and the other stays in place. This phenomenon is almost ubiquitous amongst migratory animals and has been reported in some species of fish, birds, amphibians, insects, and mammals. Despite all this, partial migration remains relatively understudied.

In order to address this shortcoming, Hamilton College’s Andrea Townsend and her colleagues captured crows in large winter flocks in Utica, New York, and Davis, California, fitting them with satellite transmitters to track their movements. The scientists also collected blood and feather samples.

Researchers found that most crows do migrate — not just to escape trying weather, but to breed. In total, 73% of western crows and 86% of eastern crows migrated at least some distance to breed, with an average journey of around 500 kilometers.

Interestingly, birds that stayed put one year also stayed put the next one — and the same thing was observed about migrating crows. It seems that their migratory behavior doesn’t change from year to year, and the birds don’t change strategies. However, they were more flexible when it came to where they spent the winter.

Researchers also note that tracking crows’ migrations (and that of other urban-dwelling creatures) are more important than ever because their migratory patterns are affected by climate change and increasing levels of urbanization.

“If you live in a place, usually a city, with a huge winter flock of crows, you are seeing migratory birds that came south for the winter as well as your local, year-round crows,” says Townsend. “Personally, I find the sight of an 8000-crow roost exhilarating, but if they or their feces are driving you crazy, you can at least take comfort in knowing that most of them will disappear in early March.”

But perhaps the most intriguing part is how much we still don’t know about these common creatures. We see them ever so often, but they’re still shrouded in mystery.

“It is surprising how much remains unknown about the seasonal movements of most partial migrant species, and this is especially true for variability among populations,” adds the Smithsonian Migratory Bird Center’s Emily Cohen, an expert on migration patterns who was not involved with the study. “This kind of information about populations-specific annual movements is not trivial to collect, but is fundamental to understanding most aspects of the evolution and ecology of species.”

The study “Where do winter crows go? Characterizing partial migration of American Crows with satellite telemetry, stable isotopes, and molecular markers” has been published The Auk: Ornithological Advances.

New Caledonian crow that made a paper card from scratch in order to receive a reward. Credit: Sarah Jelbert

New Caledonian crows can make tools from memory

New Caledonian crows are quite possibly the smartest birds out there. Their most impressive intellectual feat is their uncanny tool-making ability. Now, a new study shows that the crows are capable of fashioning tools from memory, which was thought to be impossible to do for a bird.

New Caledonian crow that made a paper card from scratch in order to receive a reward. Credit: Sarah Jelbert

New Caledonian crow that made a paper card from scratch in order to receive a reward. Credit: Sarah Jelbert

Corvids, the cosmopolitan family of oscine passerine birds that numbers crows, ravens, and rooks, are really smart. They play ahead, remember human faces, and solve puzzles.

New Caledonian crows — which live on the remote tropical island of New Caledonia in the South Pacific — are known for using twigs to stir beetle grubs and other small prey out of hiding places. They’re able to do just fine with straight twigs, but sometimes, they fashion hooked twigs — all using just their beaks and feet.

In another mind-boggling example, researchers have witnessed not one, but two crows inserting sticks into objects to carry both at once. Some of these objects were too cumbersome to carry by beak alone, which is telling of the birds’ ingenuity.

But among all of these achievements, one study published in 2002 documented a behavior that has been puzzling scientists ever science. In the study, the authors followed a captive New Caledonian crow called Betty thatt took a piece of wire, bent it into a hook, then retrieved some food otherwise out of reach. Betty used the wire after another crow had taken all the available hooks.

All of this made Alex Taylor, a researcher at the University of Auckland in New Zealand, very curious. How were these birds learning such a sophisticated behavior? The New Caledonian crows’ behavior suggested that the birds were using a sort of “mental template matching,” forming a mental picture of the tool-making process they’d seen in another bird, then copying it. This is also how humans learn new skills, through cultural transmission.

“Under the mental template matching hypothesis, New Caledonian crow tool designs could be passed on to subsequent generations if an individual used or observed the products of tool manufacture (such as their parents’ tools), formed a mental template of this type of tool design (a mental representation of some or all of the tool’s properties), and then reproduced this template in their own manufacture,” the authors of the new study wrote.

Taylor and colleagues devised an experiment to test their hypothesis, involving eight crows that were trained to drop bits of paper into a vending machine. The New Caledonian crows learned that they would be rewarded with food only when they introduced cards of a specific size, either large ones measuring 40 x 60 mm or small cards measuring 15 x 25 mm.

After this initial round of training, all the pieces of papers were taken away and replaced with a single large sheet of paper that couldn’t fit into the vending machine. The scientists then watched with their jaws dropping how the birds tore up the large piece of paper to fashion smaller pieces that matched the sizes that would earn them a reward. According to Taylor and colleagues, this is an example of “manufacturing by subtraction.”

This suggests that the crows formed a mental image of the desired object, which they then materialize into a new tool, the authors reported in Scientific Reports. Now, the researchers think that crows might also possess the ability to improve tools over time, something which they hope to test soon.

Critically endangered crow is highly skilled tool user

An international team has proved the mental prowess of a critically endangered species: the Hawaiian crow is really good at using tools.

Smart birds

A captive Hawaiian crow (‘Alalā) using a stick tool to extract food from a wooden log. ‘Alalā have relatively straight bills and highly mobile eyes — morphological features that may aid their handling of bill-held tools.
Credit: Copyright Ken Bohn/San Diego Zoo Global

For decades, the New Caledonian crow has baffled scientists with its ability to use tools. This species uses stick tools in the wild by finding small twigs and probing them into holes in logs to extract insects and larvae. They also manufacture tools by breaking twigs off bushes and trimming them to produce functional stick tools. They sometimes also exhibit meta-tool usage – they use tools to create other tools, something which requires very complex cognitive abilities.

These crows were considered an anomaly because no other corvid (crow) species exhibited such a developed intellect. But this new finding paints a completely different perspective.

“The exciting wider context is, if you have only a single species using tools, you’re trying to explain a singularity, and scientifically you’re not really winning with that,” said Christian Rutz, a behavioral ecologist at the University of St. Andrews and the lead author of the study. “But a second species provides leverage for cautiously asking evolutionary questions about how they evolved … and perhaps even to start speculating about the origin of tool use in humans.”

“I think the plot is thickening,” he added.

For over ten years, Rutz studied the New Caledonian crows. He showed that without anyone showing them how, the birds pick up twigs with their beaks and use them to scrape up food, a behavior not exhibited by any other bird species. With over 40 species of crows in nature, they seemed like the likely candidate… but which one? Crow species are generally understudied because most members live in small groups, in threatened or remote communities. Rutz couldn’t really afford to randomly fly and hope for something to happen.

But then, after a decade, he had his Eureka moment: unlike most species, New Caledonian crows have straight beaks. He performed a quick image search and found another species with the same characteristic – the large, all-black Hawaiian crow, known to Hawaiians as the ‘alalā.

Critically endangered

The ‘alalā is now sadly extinct in the wild but a last-ditch effort to preserve the species was somewhat successful. A few members still exist, in a breeding program in captivity. Without wasting much time, Rutz called the program manager, Bryce Masuda. It was a strange phone call.

“I said, ‘Look this may sound a bit crazy but I have a hunch your birds may be tool users,'” he recalled. “And the guy replied, ‘oh yeah, they do all sorts of funny things with sticks.'”

A captive Hawaiian crow (‘Alalā) using a stick tool to extract food from a wooden log. Virtually the entire species does this, without needing to be taught. (Ken Bohn / San Diego Zoo Global).

That’s when he knew he hit the jackpot. The Hawaiian crows had been using tools all along, but no one really understood – or if they did, they didn’t publish anything about this. Scientists working in the program told Rutz that they “had occasionally seen birds using stick tools at our two breeding facilities, but hadn’t thought much of it.”

After a quick observation period, they confirmed the theory.

“We tested 104 of the 109 ‘Alalā alive at the time, and found that the vast majority of them spontaneously used tools,” says Masuda. Current evidence strongly suggests that tool use is part of the species’ natural behavioural repertoire, rather than being a quirk that arose in captivity, according to Rutz: “Using tools comes naturally to ‘Alalā. These birds had no specific training prior to our study, yet most of them were incredibly skilled at handling stick tools, and even swiftly extracted bait from demanding tasks. In many regards, the ‘Alalā is very similar to the New Caledonian crow, which my team has been studying for over 10 years.”

Because so few ‘alalā survive at all, basically the entire species was studied. Many biologists expressed their compliments.

“Most studies in our field investigate just a handful of subjects, so it is truly mindboggling to see an entire species tested,” comments Professor Thomas Bugnyar, a corvid expert at the University of Vienna, Austria, who was not involved in the study.

Dark wings

In 1964, world-renowned primatologist, Dr Jane Goodall published a landmark paper in which she provided the first detailed report of tool use in wild chimpanzees. It was the first time a non-human species was shown to use tools. “Now we must redefine tool, redefine Man, or accept chimpanzees as humans,” she said. Two years after that, she also showed that Egyptian vultures use rock tools to open ostrich eggs. She was excited to hear about the new crow study and says we can already draw some comparisons between how primates and birds use tools

“I love learning about the discovery of tool use behaviours in other species of animals. This latest finding is especially wonderful. With two tool-using corvids, the well known Galapagos finches, and one vulture in the list of tool using birds, we can now make comparisons with avian and primate tool using. Each of these discoveries shows how much there is still to learn about animal behaviour, and it makes me re-think about the evolution of tool use in our own earliest ancestors.”

But the story isn’t necessarily a happy-ending one. As we said, the ‘Alalā is critically endangered – it’s extinct in the wild. Its reintroduction might be successful or it might fail, we don’t know. This means that one of the smartest creatures out there might be gone.

“Let this discovery serve to emphasise the importance to conserving these and other animal species so that we can continue to learn ever more about the range of their behaviour before they vanish for ever in the 6th great wave of extinction. We owe it to future generations.”

Credit: Wikimedia Commons

Crows are the first non-human animals we know of that employ tools to carry objects

Credit: Wikimedia Commons

Credit: Wikimedia Commons

Corvidae birds have exceptionally large brains and are adept tool users, despite having no hands, let alone opposable thumbs. New Caledonian crows are no exception. Scientists have witnessed captive crows add another remarkable tool use to their already rich repertoire. Not one, but two crows were seen inserting sticks into objects to carry both at once. Some of these objects were too cumbersome to carry by beak alone, which is telling of the birds’ ingenuity.

Four such instances were observed by researchers at Lund University in Sweden, including the slipping of a wooden stick inside a metal nut or into the hole of a large wooden ball. In all instances, both stick (carrying tool) and the hooked objects were flown away by the crows, the researchers reported in the journal Animal Cognition.

Scientists are not sure at this point if this kind of behaviour is employed by other crows or Corvidae members such as ravens in the wild. It’s possible that one of the crows was the innovator, and the other captive individual observed, learned and mimicked this. It’s really difficult to tell at this point, judging from the actions of only two individuals. But if you were to ask me, I see no reason why wild crows aren’t doing this already — to carry food too big for their beaks, for instance, and stash it for later use. Indeed, a 2002 paper published in Science recounts how a New Caledonian crow named Betty took a piece of wire, bent it into a hook, then retrieved some food otherwise out of reach. Betty was also captive, though.

Tools and objects used for insert-and-transport tool use. a Experimental square wooden stick. Credit: Animal Cognition, Springer

Tools and objects used for insert-and-transport tool use. A is an experimental square wooden stick. Credit: Animal Cognition, Springer

Wild crows doing the same wouldn’t be surprising considering their track record. Time and time again, animal behaviorists have observed crows doing amazing things with their environments to solve new problems. Besides crafting hooks to reach food from sticks, crows can recognize people’s faces and understand water displacement on the same level as a child. That’s among other amazing things. Most people don’t hold crows in high esteem due to their allegedly repulsive appearance (I think they look very cool, actually), which is a shame. By judging crows by their cover, they might be missing out on a spectacle of nature. Me, you and crows aren’t all that different in many ways.

 

This is a Eurasian Jay mated pair engaged in food-sharing. Credit: Ljerka Ostojic

Birds can infer their partner’s desires, revealing a whole new depth of mind

The Eurasian Jays are among the most intelligent birds studied thus far by biologists, belong to the corvids, a group of birds that also includes crows. The latter are especially gifted, as they’ve been observed making use of tools, associate faces with behavior and even recognize when a fellow crow has died. Quite crafty fellows. Ravens, which also belong to the same family of birds, use gestures to communicate with their peers.

This is a Eurasian Jay mated pair engaged in food-sharing. Credit: Ljerka Ostojic

This is a Eurasian Jay mated pair engaged in food-sharing. Credit: Ljerka Ostojic

Back to the jays, though, since this time they’re at the center of attention after researchers at Cambridge University found that males would often feed their partners based on what the females’ desires. This suggests that jays are capable of recognizing and understanding the internal life and psychological states of others – something scientists call “state-attribution”.

A bit of background on the jays feeding behavior, first. You would think anything remotely looking like food would do for the jays, but these monogamous birds are quite picky. It’s well known that jays often stockpile food for later use, not only out of a sense of security for tomorrow’s meal, but also for variety. Bet you didn’t know that.

The researchers tested pairs of jays to see how well the male partner could infer the female’s intentions. Thus, the pairs were separated; the female was introduced in a compartment where it was fed with one particular larvae, either wax moth or mealworm – both considered delicacies in the jay world. In the meantime the male would watch from an adjacent compartment through a transparent window.

The pairs were then reintroduced. They found that when the male was given the chance to present food to his mate, he would offer the female a kind of food she previously didn’t have access to. So for instance, if the female was initially fed one type of larva, the male would choose to present the other type of larva the female hadn’t ate yet. Something most welcomed by the female, as the researchers note.

Multiple types of food were used, but the behavior was the same – the male would diversify the female’s food, known it would be to her liking. Visual access was also varied, allowing the researchers to prove that the males needed to see what the females were eating in order to present the best mix. This rules out the possibility that the female might signal the male with some sort of sign to bring a desired kind of food.

“Our results raise the possibility that these birds may be capable of ascribing desire to their mates – acknowledging an ‘internal life’ in others like that of their own,” said Ljerka Ostojic, who led the research. “Ascribing internal states to other individuals requires the basic understanding that others are distinct from the self and others’ internal states are independent from, and differ from, one’s own.

The implications of this are quite extraordinary, since it puts the jays in a behavioral and psychological range previously thought to be reserved to primates only – an ability to infer your peer’s minds. Scientists refer to this as the “theory of mind”, which I recommend you look up a bit.

Findings were reported in the journal PNAS.

A male raven showing off an object in his beak to his peers. "Hey raven-lady, look at my thing! Here's some stuff, wanna touch it?" (c) Thomas Bugnyar

Ravens use gestures to point out things and communicate

We’re inclined to think that gestures are reserved to species which at least possess some kind of articulated limbs. However, scientists have shown that wild ravens purposefully gesture, making it the first time this type of be­hav­ior has been ob­served in the wild ex­cept in the clos­est rel­a­tives of hu­mans, primates.

A male raven showing off an object in his beak to his peers. "Hey raven-lady, look at my thing! Here's some stuff, wanna touch it?" (c) Thomas Bugnyar

A male raven showing off an object in his beak to his peers. “Hey raven-lady, look at my thing! Here’s some stuff, wanna touch it?” (c) Thomas Bugnyar

Sure, you might argue that you’ve seen your dog maybe come out at you and move or touch you with its snot to show you a certain direction, most likely where you keep your food. Researchers claim, however, that these aren’t naturally developed gestures, instead, they’ve been infused by training.

In the new study, Si­mone Pi­ka of the Max Planck In­sti­tute for Or­nith­ol­o­gy in Mu­nich, Ger­ma­ny, and Thom­as Bugn­yar of the Uni­vers­ity of Vi­en­na ob­served wild rav­ens in the Cum­ber­land Wild Park in Grü­nau, Aus­tria. What they observed amazed them greatly.

RELATED: Urban birds have bigger brains

The ravens would use their beaks in the manner a human uses its hands to show and of­fer ob­jects such as moss, stones, and twigs. Like all super-efforts on Earth, these gestures were directed towards the opposite sex. As if gesturing wasn’t enough, the ravens would sometime interact with each other using the object, as the researchers could observe the ravens touching or clasping their bills together, or by manipulating the item together.

“Most exciting is how a species, which does not represent the prototype of a ‘gesturer’ because it has wings instead of hands, a strong beak and can fly, makes use of very sophisticated nonvocal signals,” Pika told LiveScience.

Ravens, and their close relatives, crows, and magpies, have been found to be of extreme intelligence for a bird, some actually rivaling great apes in tests, and rav­en mat­ing pairs show rel­a­tively com­plex com­mu­nica­t­ion and high coop­era­t­ion. The latter part is of severe importance since a further study of the raven, correlated with other data, might help decipher the origin of gesture in human beings.

“Ges­ture stud­ies have too long fo­cused on com­mu­nica­tive skills of pri­ma­tes on­ly. The mys­tery of the ori­gins of hu­man lan­guage, how­ev­er, can only be solved if we look at the big­ger pic­ture and al­so con­sid­er the com­plex­ity of the com­mu­nica­t­ion sys­tems of oth­er an­i­mal groups,” said Pi­ka.

The researchers’ findings were published in the latest issue of the journal Nature Communications.

Urban birds have bigger brains

Researchers have concluded that urban dwelling birds forced to adapt and innovate in a concrete environment have a larger brain, relative to their body size. In the process, scientists have found family traits are key to identifying why certain birds thrive in certain European cities, and consequently generally in urban environments.

Urban bird achievers include tits, crows, nuthatches and wrens which all come from families of related species that have large brains compared to their bodies. Living in the city is no easy task, one which breaks the natural pattern of trees, plains and so on these species have been used to for thousand of years, and whose habitat has significantly changed over the past few hundred years as the industrial age boomed, and urban centers flourished.

Living in the city requires innovation and adaptation, and for that you need a bigger brain, and scientists took to find out why some particular species of birds are doing much better than others in the city. With this in mind, researchers from the Evolutionary Biology Centre, Uppsala, Sweden and the Donana Biological Station, Seville, Spain studied 82 species of birds from 22 families. Focusing on 12 cities in France and Switzerland, they aimed to find out why some species of bird are more successful in urban environments than others.

“We were interested whether behavioural flexibility can increase the chance of a given species to successfully colonise cities,” explained evolutionary biology expert Dr Alexei Maklakov.

“After all, a centre of a modern city is a novel and rather harsh environment for most species and the ability to sustain a varied diet or develop novel foraging techniques and perhaps utilise non-standard nesting places, can be beneficial.”

Previous studies have highlighted the link between larger brains and behavioral innovation in birds and mammals, and this one provides results no different – birds breeding in city centres, or “urban adapters” as the team called them, were found to have larger brains relative to their body size. This adds even more value to the hypothesis that brain size is a key factor for animals’ survival in urban environments.

Some small-brained species, such as barn swallows, survive in cities though, very well too, but to the scientists conducting the study they cannot be considered true “urban adapters” according to Dr Maklakov.

“Some of [the small] brained species are lucky enough to find niches in urban habitats that are by coincidence a pretty good approximation of their original habitat,” he said.

Dr Maklakov suggests that the specific ecological niches which support small-brained species are simply exceptions and thus cannot be considered true “urban adapters”. The team say their findings could prove useful for future conservation efforts.

“[The study] suggests that some species and even whole families of birds are less likely to adapt to novel conditions and if we want to see them in the cities we will have to create patches of their original habitat,” said Dr Maklakov.

Their findings are available in the journal Biology Letters.