Three tools are better than one for New Caledonian crows when it comes to attaining a treat, a team from the University of Oxford reports.
Captive crows were presented with four horizontal tubes. One of the tubes contained some out-of-reach food; the others contained long and medium-length hooks - but again, these were all out of beak's reach; a shorter hook-like tool was positioned nearby.
The researchers found that the birds picked up the short tool, then used this to grasp the medium tool, which they then employed to retrieve the longest tool from the tube, with which, finally, they could drag out the tasty morsel.
These birds, which are found on the Pacific island of New Caledonia, are known to use tools in the wild, but this study, published in the journal PLoS One, builds on their tool-using repertoire.
Footage courtesy of the University of Oxford's Behavioural Ecology Group