They are so remarkable they rose to become a favourite pet the world over, but now they are rebounding in numbers in their original diminutive size in aviaries in Amaroo, Bungendore, the Sydney suburb of Croydon and beyond.
Budgerigars have been so mutated over the years that they dwarf the original bush budgies, but breeders such as Joe Forshaw in the ACT and Warren Wilson of Sydney have never forgotten the wild birds from their boyhood days.
Sixty years ago, Mr Wilson was on his way to the races at Parkes with his grandfather when they saw a green paddock among the lumpy, brown, ploughed fields. When a passing truck blew its horn, the ''paddock'' took off.
''There were hundreds and hundreds of thousands of budgies. They swooped up, creating a cloud blocking out the sun,'' Mr Wilson said. ''After 10 or 15 minutes, they landed on the paddock and it became green again.''
Mr Forshaw grew up in Dubbo where wild parrots sparked a life-long fascination. He become a world-leading expert on parrots and bred wild budgies on the north coast.
Back then a breeder and sanctioned importer of English budgies told him he could not enter his wild budgies in shows because there was no class for them. ''I remember saying 'but these are the [original] budgies','' Mr Forshaw said.
Mr Wilson said there were about 17 members of the Australian Bush Budgie Organisation, an offshoot of Budgerigar Rare and Specialist Exhibitors of Australasia and the Sydney Royal Easter Show now has a bush budgie section.
Mr Forshaw and Mr Wilson have never met, but they share same enthusiasm for the birds.
''They are becoming popular as people realise they are a beautiful little bird,'' Mr Forshaw said.
''A bush budgie is far more active and very funny, a real fun thing to have around,'' Mr Wilson said. ''They are tiny, they get right into stuff, they are devils for punishment, they love acrobatics. I breed mine on a colony system, so they decide when they want to breed.''
He has about 70 and, after rain, the hens disappear into nesting boxes and chicks hatch 18 days later - the same number of days it takes for grass seed heads to appear. ''It's like someone telling them: 'It rained, go nest, because when you're ready the seeding grasses will be ready and you can feed your chicks'.''
Mr Wilson said bush budgies could be aggressive. ''If a hen goes into the wrong box there's a donnybrook on, but they'll breed like steam far better if you set up a colony aviary. If you have five hens, put seven boxes in. With only five boxes they'll fight over the bloody things. You can bet your boots that two hens will want the same box.''
Mr Forshaw said budgies had never survived overseas in any feral population except in Florida, but even there they depended on feeders.
Bungendore bird fancier Bob Elgood, who bred Mr Forshaw's bush budgies, said the bush birds were hard to find, which is reflected in high prices they fetch, even though they were easy to breed.