Researchers have documented wild crows creating and using hooked tools. While experiments in controlled settings have shown that New Caledonian crows, widely considered as one of the most intelligent species of bird, can fashion tools with hooks to reach food, no one had previously recorded this in the field. Using tiny video cameras attached to the birds, scientists were able to capture the exact moment that some of the crows made the implements, giving them insight into how the birds use such tools in the wild.
New Caledonian crows are well-known for their innovative use of tools. Numerous experiments have shown how the birds can use their bills to whittle twigs and leaves to make tools that allow them to extract food, such as grubs and insects, from hard-to-reach places. Not only that, but they’ve also been shown to display “meta-tool” use, in which they use one tool to retrieve another, which they then use to get the food, and to also use twigs to investigate and prod something they’re unsure of. But getting evidence of this in the wild has always been tricky.
New Caledonian crows are renowned for their problem-solving skill, such as the one shown here demonstrating one of Aesop’s fables. PLOS Media/YouTube
“New Caledonian crows are notoriously difficult to observe,” explains Dr. Jolyon Troscianko, who coauthored the study, “not just because of the challenging terrain of their tropical habitats, but also because they can be quite sensitive to disturbance. By documenting their fascinating behavior with this new camera technology, we obtained valuable insights into the importance of tools in their daily search for food.”
The researchers stuck the tiny cameras to the birds’ tails, and designed them so that they would drop off after a few days of recording, allowing the team to retrieve them and watch the birds’ behavior. They did this to a total of 19 individuals, and recorded over 10 hours’ worth of footage. During this period, they filmed two instances of the crows crafting hooked tools in the wild. They then used these to extract grubs from crevices in trees, and to search through leaf litter on the floor.
The cameras also gave the researchers further insight into the birds’ tool-using behavior. “In one scene, a crow drops its tool, and then recovers it from the ground shortly afterward, suggesting they value their tools and don't simply discard them after a single use,” says Dr. Christian Rutz, another of the authors of the study published in Biology Letters. In fact, they even observed the crows storing the tools in tree holes, to keep them safe so they can use them again later on.