Yes as I said by one very experienced aviculturalist who took 5 years to achieve his first success. I am not aware of any other captive breeding until the recovery program established a breeding program in the 1990's.
Either way, captive breeding was learned 20 years ago at least. Enough, for a fast breeding parrot, to have a captive insurance population in the thousands.
Now that made me laugh. You obviously don't know much if anything about the wild condition of the parrots. They migrate about 600km. The first quarter of the migration is across a wilderness, ie no walking tracks let alone roads, The second quarter is through a region with one north-south road servicing fewer than a dozen small settlements. The last half is across an open ocean with a couple of islands available for rest. Only one island has a settlement. Arriving on the mainland they disperse along a coastal strip a 1,000km long, much of which is not accessible by car.
Much, but not more difficult than follow a thrush all across the USA.
On the mainland, only part of the area has habitat used by the parrots. And it would become more easy to find, if birds had transmitters put on the breeding grounds, which would give away their location from >10km away.
Do you have any sources suggesting that introduced birds are a threat to orange-bellied parrots? As for predators you seem to be suggesting gunmen should be patrolling a 1000km of coast, shooting every hawk and falcon on sight. The birds evolved with predators, they are not the cause of their current predicament.
Birdlife official site, for a start:
Orange-bellied Parrot (Neophema chrysogaster) - BirdLife species factsheet
Conservation and Research Actions Proposed
(...)Control predators at mainland sites. Control feral cats at King Island site.(...)
I am beginning to understand why professionals don't engage with this site.
I appreciate your self-criticism. I, indeed, would very much welcome information from a professional.
