- [Narrator] This experiment is designed to compare how New Caledonian crows and kea solve problems.

Wek represents the crows, and for the kea parrots, this is Kermit.

Their reward: a peanut.

Their challenge is called a multi-access box.

The first time both birds see the puzzle, they make the same choice.

They just pull the string.

Then the researchers take that solution away to see what they'll do next.

Wek uses the stick to poke the nut free, but this isn't a surprise.

- New Caledonian crows are very special because they're the only crow species that use tools in the wild.

They obtain a lot of their diet by using tools.

- [Narrator] Kea parrots don't use tools in the wild, but Kermit figures out a solution with the ball and chute.

Again, the researchers remove the option that's been used.

For Wek, the hole for the stick is taped over.

Wek has to try something else, so she tries the ball and chute.

With two choices left, Kermit just opens the door, reaches inside, and takes the peanut.

But Wek won't take this approach.

- The last thing a crow wants to ever do is stick its head in something.

They're extremely vulnerable if they do that and to stick their head inside that box, it could trap them in it.

- [Narrator] Wek still opens the door, but rather than put her head inside, she pokes the nut free with a stick.

Kermit's last option is the stick.

His curved beak makes it very hard to hold, but he still sees this as a potential solution, even though it's not easy.

Both birds found four different solutions to the puzzle, showing they're able to think flexibly.