Intelligence and flight allowed crows to colonize the world

Humans, crocodiles and crows have something in common, they have spread to all corners of the planet. From Barcelona to Australia, despite the enormous distance, we will find groups of animals such as owls, swallows, turkeys, crows or humans. All these animals are so far away because they managed to colonize almost the entire planet. But what makes them able to do so while other groups of animals have been reduced to small areas of the planet?

Co-led work between Washington University in St. Louis and the Center for Ecological Research and Forest Applications (CREAF) focused on crows to answer that question. One of the conclusions of the work was that crows could have colonized the planet thanks to their ability to fly long distances, a large body and use intelligence to solve problems and obtain new resources from each environment.

For researchers Daniel Sol and Joan Garcia-Porta, the first also a researcher at the CSIC and the second now in the Department of Genetics, Microbiology and Statistics at the University of Barcelona, ​​these three characteristics coincided correctly in the group of crows and allowed them to arrive to remote places, survive in environments of all kinds and adapt to them successfully.

What was the consequence of this global expansion? An exceptional diversification. The study shows that crows, as they spread across the world, produced new species at an exorbitant rate: more than 40 different species in just ten million years, species that changed their body size and beak shape to adapt. to new environments.

To reach these conclusions, the research team carried out an exhaustive analysis of a multitude of ecologically relevant traits: the size of the wings, the volume and shape of the beak, the dimensions of the body and the size of the brain. For this, he visited museums around the world to measure and compare skeletons of many species of corvids, that is, the family of crows that also includes rooks, magpies and jays, among other species.

“Natural history museums are amazing places, true biodiversity archives. In a small space you can see and compare an infinity of different species, many of them from distant corners of the planet”, explains Joan Garcia-Porta, also a member of the Institute for Research in Biodiversity (IRBio) at UB.

In parallel, the phylogenetic tree of the corvid family with genetic data to incorporate as many species as possible. Combining phylogenies and morphological traits, it was possible to verify whether these traits, in addition to helping to colonize the world, also accelerated the creation of new species.

Quasi-planetary distribution of crows, genus Corvus. / Miguel Vences

flying machines

The results of the study show that crows have relatively longer wings than crows. rest of corvids and they have larger body sizes. This allows them to fly great distances and, once they arrive at a new location, to be competitively superior. Being good fliers also helps you to randomly travel to remote places, which drastically decreases your genetic exchange between populations and facilitates the generation of new species.

To this we must add that each new location may have different conditions from the previous one, to which the species had to adapt, modifying its morphology with each new condition. This explains why, as crows spread across the world, they increased the number of species at great speed, producing a huge variation in body size and beak shape.

unique intelligence

ONE colonizing animal It must be able to survive in new environments that are certainly very different from the originals, from arctic to desert zones. What morphological characteristic facilitates being more or less able to adapt to a new environment? Daniel Sol’s research group has been working on this issue for many years and is very clear: the size of the brain.

“Intelligence in animals is demonstrated when an individual is able to solve challenges and overcome limitations or imbalances that occur when the environment changes. This implies having a relatively larger brain size, because it has been shown to be related to having more cognitive abilities and a lot of behavioral flexibility, a well-known characteristic of crows,” comments Daniel Sol.

With that premise, the team measured the brain volume of more than 76 species of crows and other corvids. The results were as expected, crows have a larger relative brain size than the rest of the corvids. “The fact that they have larger brains shows that crows may have greater cognitive abilities than other corvids, which allows them to have the necessary adaptability occupy environments as different as the arctic tundra and the Australian deserts”, explains Joan Garcia-Porta.

More than 3,000,000 observations

The researchers also wanted to see if, in fact, crows were able to live in climatic zones where no other corvid lives. To do this, they extracted more than three million observations of corvids from the eBird citizen science platform. This gave information about the climate space where the crows lived (where they were observed), and they were able to compare it with the climate space of the rest of the corvids.

The results, once again, showed that crows occupied a much wider climatic range than all corvids combined and that, in addition to replicating the climatic space occupied by other corvid species, they reach much more extreme climatic zones where no corvid can. survive.

“Crows offer us a fantastic opportunity to understand why certain organisms spread and diversify across the planet. We are one of those organisms and therefore understanding the processes of global expansion in other groups of animals we know if they can shed some light on our own journey across the planet”, concludes Joan Garcia-Porta.