Hawaiian crows are among the world's only birds with an ability to forage for food using tools, scientists have said. While crows are known to be particularly smart, this rare and remarkable behaviour had so far only been identified among corvids in New Caledonian crows.
For many years, scientists have been baffled by New Caledonian crows' sophisticated tool-making skills. Using sticks, the birds are able to recover food from intricate locations.
However, the evolutionary origins of this species' impressive tool behaviour remain a mystery, because no naturally tool-using birds from the same genus have been identified to date to allow scientists to make comparisons.
In the study published in the journal Nature, scientists have finally observed advanced tool use in another crow, the Hawaiian crow – also known as alala.
This bird became extinct in the wild at the beginning of the century, and just over a hundred remain in captivity today, but it managed to impress scientists as it displays a particularly high level of intelligence.
Selecting and using the 'tools'
In this study, researchers worked with 104 of 109 surviving Hawaiian crows. They tempted them with meat buried in holes and narrow crevasses within wood. They found out that 78% of them spontaneously used stick tools to probe for food that they could not reach. They also appeared to carefully select the sticks they were going to use, or even to cut them when they were too long.
" We were surprised at just how good alalas are at using tools, they are just incredibly fast, even compared with New Caledonian crows. We have also observed alalas selecting different types of tools, exchanging them when they were not happy with the tools", said lead author Christian Rutz, from the University of St Andrews.
The team also found that tool use varied with age, with 93% of all adult crows using tools compared to 47% of younger birds. What was incredible is that young crows appeared to naturally develop abilities with tools, even without the opportunity to learn from their elders. This suggests that proficient tool use is a species-wide capacity.
Both birds have evolved in similar environments on remote tropical islands, and since they are only distantly related, the authors believed their technical abilities arose convergently. "This supports the idea that avian foraging tool use is facilitated by ecological conditions typical of islands, such as reduced competition for embedded prey and low predation risk", the authors write.
Next, the scientists will release some of the crows in the wild to observe them and see if this ability with tools is also present and not simply developed in captivity.