A new study has found that crows go through painstaking efforts to create tools — this behavior allows them to get more food and is probably what led to them developing advanced cognitive abilities.

A crow standing proud with the tool it crafted. Image credits: Pedro Barros da Costa and Rutz Groupd.

We’ve known that crows are smart for quite a while. Their ability to use tools and solve puzzles has impressed scientists time and time again, but not that much is known about how this behavior benefits them in the wild. In a new study, Scottish researchers focused on New Caledonian crows, birds which live on the remote tropical island of New Caledonia in the South Pacific.

New Caledonian crows 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. It’s not easy to make tools when you don’t have hands, and all you’ve got is your beak and feet.

A crow using its tool to stir out some food. Image credits: James St. Clair.

“It’s a painstaking sequence of behaviours,” explains lead author Dr James St Clair, from the School of Biology, University of St Andrews. “Crows seek out particular plant species, harvest a forked twig, and then – firmly holding it underfoot – carve, nibble and peel its tip, until it has a neat little hook.”

This behavior has been previously observed, but the St. Andrews researchers wanted to quantify the crow’s return on investment from manufacturing hooks, so they recorded how much food crows with hooked tools get, compared to crows with straight tools. The results were stunning: hooked tools yield between 2 and 10 times more food than regular tools.

It’s not the early bird that catches the worm — it’s the skilled hookmaker.

“That’s a huge difference!” says project leader, Professor Christian Rutz from the University of St Andrews. “Our results highlight that even relatively small changes to tool designs can significantly boost foraging performance.”

This could also explain why the birds have such a great incentive to learn to develop tools. Researchers still don’t know if this ability is innate — whether the birds inherit it from their parents, or they learn it by observing others. But either way, these are some very clever birds.

“In nature, getting food quickly means that birds have more time and energy for reproduction and steering clear of predators. It’s really exciting that we were able to measure the benefits of these nifty crow tools,” adds study co-author Professor Nick Colegrave from the University of Edinburgh’s School of Biological Sciences.

The paper ‘Hook innovation boosts foraging efficiency in tool-using crows’ is published in the journal Nature Ecology & Evolution (22 January). DOI: http://dx.doi.org/10.1038/s41559-017-0429-7.

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