New Caledonian crows make hooked tools from soft twigs to scoop insects out of holes. Other animals that use tools: chimpanzees, parrots, alligators and crabs.
The crows found the desired stems even when they had been disguised with leaves from a different plant species.
Convergent Evolution: The crows lack a neocortex (assumed to enable advanced cognition). They instead have densely packed clusters of neurons.
We’re not the best at every mental task, e.g. chimps have better short-term memories. Ranking the intelligence of animals might be pointless. The real question is how well that animal is adapted to its niche.
Which makes the “Crows Could be the Smartest Animal Other Than Primates” title ironic. The authors didn’t follow their own advice.
A New Caledonian solved an artificially constructed puzzle involving 8 distinct steps. It had learned how the individual steps work, but solving them in sequence is a greater challenge.
Crows have a natural curiosity. They cheekily grab scientific equipment and fly off with it in the aviary. Young birds especially love to play.
Sidenote: (probably exxagerated War of the Crows) .
There are anecdotes of crow intelligence too, e.g. using cars at a crosslight to crush cashews in Japan (more in this HN thread )