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Crows in New Caledonia Can Use Several Tools To Reach Food

Dec 23, 2015 03:17 PM EST

Recent footage of New Caledonian crows documents for the first time how the birds build and use complex tools in the wild. Researchers from the Universities of Exeter and St. Andrews discovered the tropical corvids will make hooked stick tools to reach food deep in tree crevices or hidden under leaf litter.

"While fieldworkers had previously obtained brief glimpses of hooked stick tool manufacture, the only video footage to date came from baited feeding sites, where tool raw materials and probing tasks had been provided to crows by scientists," Dr. Jolyon Troscianko, one of the study researchers and a Postdoctoral Research Fellow in Exeter's Biosciences Department, explained in a news release. "We were keen to get close-up video of birds making these tools under completely natural conditions."

To obtain a 'crow's-eye view' of this elusive behavior, tiny cameras were attached to the tail feathers of 10 crows. When combing through the video footage, researchers observed two instances of hooked stick tool making, as well as one crow spending time using the crafted tools to acquire otherwise inaccessible food. 

"New Caledonian crows are notoriously difficult to observe, 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," Dr. Troscianko added in Exeter's news release.

New Caledonian crows (Corvus moneduloides) are all-black, medium-sized members of the Corvidae family, native to the South Pacific island of New Caledonia. These birds have a broad diet, consisting of insects, eggs and nestlings, small mammals, snails, and various nuts and seeds - much of which requires strategic foraging.

"The behavior is easy to miss - the first time I watched the footage, I didn't see anything particularly interesting," Troscianko noted, "Only when I went through it again frame-by-frame, I discovered this fascinating behavior. Not once, but twice!"

To create their hook tools, researchers say the birds use their bills to whittle twigs and leaves into bug-grabbing implements. This innovative behavior is comparative to the tool-making abilities observed in primates. 

"In one scene, a crow drops its tool, and then recovers it from the ground shortly afterwards, suggesting they value their tools and don't simply discard them after a single use," Dr. Christian Rutz, from the University of St. Andrews, explained. "Crows really hate losing their tools, and will use all sorts of tricks to keep them safe. We even observed them storing tools temporarily in tree holes, the same way a human would put a treasured pen into a pen holder."

Their findings were recently published in the journal Biology Letters

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