By creating miniature video cameras and attaching them to wild New Caledonian crows, two researchers from the UK have obtained footage showing how the resourceful birds fashion hook-like stick tools that they then used to hunt for insect prey.
Thanks to their invention, Dr. Jolyon Troscianko from the University of Exeter and Dr. Christian Rutz from the University of St. Andrews were able to record two instances of the tropical corvids constructing their tools—including one that took a crow a little over one minute to build.
The birds then used their tools to help them search for food in tree crevices and leaf litter on the ground, the study authors reported Wednesday in the journal Biology Letters. This marks the first time that the tool-making behaviors of these crows has ever been caught on film.
“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. We were keen to get close-up video of birds making these tools under completely natural conditions,” Dr. Troscianko, a postdoctoral researcher in Exeter’s Biosciences Department, said in a statement.
Footage shows that crows place a high value on their instruments
Dr. Troscianko noted that it is “notoriously difficult” to observe New Caledonian crows, due to their tropical habitats as well as the fact that they can be easily disturbed. “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,” he added.
So how did they do it? They created special, tiny video cameras that weighed roughly the same as a British two-pound coin, and attached them to the tail feathers of the crows. Each camera had a miniscule radio beacon integrated into it that allowed the researchers to recover them after they had monitored the birds for a few days, Dr. Ruiz explained.
“These cameras store video footage on a micro-SD card, using technology similar to that found in people’s smart phones. This produced video recordings of stunning quality,” he said. The team used a total of 19 cameras, and as they reviewed footage, they found two instances of the tropical birds fashioning the bug-catching tools out of twigs and leaves.
The researchers said they had to go through the footage frame-by-frame because the activity was hard to spot at first, and not only did they catch two instances of the birds fashioning these tools, but they also saw one crow recover a finished tool that it had dropped. Dr. Ruiz believes that this indicates that the crows value their tools, and do not simply dispose of them after use.