Crows are no bird-brains! Scientists have for the first time demonstrated how the brains of crows produce intelligent behaviour when the birds have to make strategic decisions.
Researchers have long suspected that corvids - the family of birds including ravens, crows and magpies - are highly intelligent.
Behavioural biologists have even called crows "feathered primates" because the birds make and use tools, are able to remember large numbers of feeding sites, and plan their social behaviour according to what other members of their group do.
This high level of intelligence might seem surprising because birds' brains are constructed in a fundamentally different way from those of mammals, including primates - which are usually used to investigate these behaviours.
Neurobiologists Lena Veit and Professor Andreas Nieder from Eberhard Karls University of Tubingen in Germany investigated the brain physiology of crows' intelligent behaviour.
They trained crows to carry out memory tests on a computer. The crows were shown an image and had to remember it. Shortly afterwards, they had to select one of two test images on a touchscreen with their beaks based on a switching behavioural rules.
One of the test images was identical to the first image, the other different. Sometimes the rule of the game was to select the same image, and sometimes it was to select the different one.
The crows were able to carry out both tasks and to switch between them as appropriate. That demonstrates a high level of concentration and mental flexibility which few animal species can manage - and which is an effort even for humans.
The crows were quickly able to carry out these tasks even when given new sets of images. The researchers observed neuronal activity in the nidopallium caudolaterale, a brain region associated with the highest levels of cognition in birds.
One group of nerve cells responded exclusively when the crows had to choose the same image - while another group of cells always responded when they were operating on the "different image" rule.
By observing this cell activity, the researchers were often able to predict which rule the crow was following even before it made its choice.
The study published in Nature Communications provides valuable insights into the parallel evolution of intelligent behaviour.
"Many functions are realised differently in birds because a long evolutionary history separates us from these direct descendants of the dinosaurs," said Lena Veit.
"This means that bird brains can show us an alternative solution out of how intelligent behaviour is produced with a different anatomy," Veit said.
