Only a single example of the brilliant blue macaw remains in its natural home in the forests of north-east Brazil, but as many as 50 birds are held in captivity by two wealthy parrot fanciers in Switzerland and the Philippines, according to the British-based World Parrot Trust.
Michael Reynolds, director of the trust, said a reintroduction programme could not go ahead because of the lack of interest of the collectors. "They are holding the future of the world's rarest bird in their hands," he said.
His comments came as it was revealed that nearly a third of the world's parrot species are now in danger of extinction. Habitat loss, such as the destruction of tropical forest, has now combined with the vast global pet trade to set 90 of the 330 parrot types on the road to disappearance, according to the trust and the World Wide Fund for Nature (WWF). This makes parrots the most endangered bird family on Earth.
Launching an international action plan to save them, the two bodies called for recovery teams to be set up for each threatened species and for wildlife trade rules to be much more strictly enforced. Dr Paul Toyne, WWF conservation officer, said: "Governments must take firm action to increase protection for forest habitat and enforce the convention which regulates the trade in wild animals."
Species teetering on the brink of extinction include the world's biggest parrot, the flightless kakapo from New Zealand, down to 56 individuals; Lear's macaw from Brazil, with fewer than 150 birds; and the echo parakeet from Mauritius, down to eight birds 15 years ago, but now, thanks to a captive breeding programme, with a population of more than 100.
Mr Reynolds named the two private owners of Spix's macaws as Antonio DeDios, an industrialist from Manila who he said had 30 to 40 birds, and Dr Josef Hammeli, a Swiss dentist, thought to have 10.
But when contacted by The Independent last night, Dr Hammeli said he had sold his birds: "I have no more parrots any more. I stopped several weeks ago. I sold them all to another collector. I can't tell you his name but he lives in Switzerland. I stopped keeping them for health reasons."
Tony Juniper, policy and campaigns director for Friends of the Earth, and an international parrot expert who discovered the last Spix's macaw in the wild in 1990, was angryat the news of the sale.
He said: "The sale of these birds emphasises the disgraceful nature of the trade in endangered wildlife. It has more similarities to the trade in illegal works of art than it does to any serious conservation programme."
SPIX'S MACAW Cayanopsitta spixii. Now virtually extinct in the wild. One male remains in the north Brazilian state of Bahia. Discovered in 1990. Has been seen trying to mate with a Illiger's macaw, Propyrrhura maracana. Perhaps 50 in captivity.
RED-TAILED AMAZON Amazona brasiliensis. Found in the coastal areas of the Brazilian states of Sao Paulo and Parana, only about 4,000 to 6,000 birds remain.
LEAR'S MACAW Anodorhyncus leari. One of the world's rarest birds, with an estimated 139 left in the valley of the Rio Vasa Barris in Bahia, Brazil.
Large flightless parrot from New Zealand, hunted close to extinction by introduced predators such as stoats.
ST VINCENT AMAZON Amazona guildingii. About 800 thought to be left in its only home, the West Indian island of St Vincent. Hit by hunting and loss of habitat.