A crow and a parrot have shown scientists what their bird brains can do in a remarkable contest of cleverness.

The result was effectively a draw. Each participant overcame a series of testing tasks, while finding different challenges more difficult or easy.

Kermit, the kea parrot, and Uek, the New Caledonian crow, were both confronted with a “multi-access box” barring their way to a food reward.

The birds had a choice of four solutions to the problem. They could pull a string tied around the reward, open a window using a hook-shaped lever, insert marbles into a chute so that they knocked the reward within reach, or insert a stick-like tool into the side of the box to poke the food out.

Six parrots and five crows took part in the study, but only Kermit and Uek mastered all four tasks.

The scientists allowed the birds to select a preferred solution and then blocked it off, so they had to work out another. One by one they were asked to overcome each obstacle in turn. For Kermit, the most difficult task was using a stick as a tool - something keas never did in the wild, unlike New Caledonian crows.

Austrian biologist Alice Auersperg from the University of Vienna, who led the study, reported in the online journal Public Library of Science ONE, explained: “The kea’s curved beak makes it impossible for them to hold a stick aligned with the head. Kermit overcame this constraint by developing a complex technique, involving several steps: he first held one end of the stick against the box opening, holding it laterally inside its beak.

“Thereafter he exchanged his beak with his foot, still pressing the tool’s end against the opening. Finally, he grabbed the other tool end with his beak and pushed the tool through the opening, manoeuvring it until the stick’s tip hit the reward. Kermit’s behaviour gave a strong impression of acting towards a purpose.”