The Norfolk Island Boobook Owl Ninox novaseelandiae undulata is one of the rarest birds on earth.
The boobook was almost extinct in the mid-1980s, with just one female bird left on the island - and therefore the world. Thankfully it has been saved from extinction through crossbreeding with closely-related morepork owls from New Zealand. After a concerted effort numbers grew to around 40 owls.
You can hear their particular 'boo-booork' call from dusk until midnight, especially on warm moonlit nights.
https://en.wikipedia.org/wiki/Norfolk_boobook
BYOP