Researchers presented 10 birds with a box containing a cashew nut treat, which they could reach by removing five different interlocking devices.
One of the Goffin's cockatoos, called "Pipin", solved the complex mechanical puzzle unassisted within two hours.
Several other birds mastered the task after observing peers or being presented with the locks incrementally.
To reach the nut, the captive Goffin's cockatoos (Cacatua goffini) had to remove a pin, followed by a screw, a bolt, then turn a wheel and move a latch sideways.
"The progress of the birds towards the solution is unaffected by the fact that the goal is very distant," said Professor Alex Kacelnik from the University of Oxford's department of zoology, who co-authored the study.