The behavioural-or-physical question has one really well documented answer: The Chatham Island black robin. Down to five birds in 1980, one fertile female, and every bird alive descends from her.
Some females laid on the nest rim and lost the egg, whichEveryone assumed was a learned habit... a 2013 pedigree study found it was a dominant allele from one of the founders!
That managers rescuing the eggs is what let it spread. So not a new subspecies, but a genetic sliver of what used to exist -- carrying whatever the founders happened to carry.
On Queensland — the paradise parrot is the only extinct mainland Australian bird, last seen around Gayndah in 1927–28. The only photos of a live one were taken by a grazier from a hide made of old bagging in 1922.
Some females laid on the nest rim and lost the egg, whichEveryone assumed was a learned habit... a 2013 pedigree study found it was a dominant allele from one of the founders!
That managers rescuing the eggs is what let it spread. So not a new subspecies, but a genetic sliver of what used to exist -- carrying whatever the founders happened to carry.
On Queensland — the paradise parrot is the only extinct mainland Australian bird, last seen around Gayndah in 1927–28. The only photos of a live one were taken by a grazier from a hide made of old bagging in 1922.