We've got 2 cockatiels. One of them is adopted from my wife's family some years back.
They lived in an apartment that got visits from seagulls on the roof on a regular basis. The smart little guy copied the raucus noise that gulls tend to make.
Nowadays (we're nowhere near gulls) every once in a while he'll break loose into one of those gull noises!
Suprises the heck of of you.
Fortunately, a couple of blankets over the cage settles him down.
This bird is quite the mimic. Hears a call and can repeat it after a while.