Phoebe Snetsinger, 68, from St Louis, Missouri, died instantly when a tour minibus overturned in Madagascar last Tuesday as she slept in the back. Other passengers escaped with injuries.
Mrs Snetsinger took up her bird-based globetrotting after she was diagnosed with cancer 18 years ago, and became famous through catching in her binoculars more than 80 per cent of the planet's known bird types.
Her final total stood at more than 8,300 out of about 10,000 known species - a feat thatearned her a place in the Guinness Book of Records, and which no fellow twitcher is near to challenging.
Her travelling - she had just returned from Australia before going to Madagascar three weeks ago - began after doctors diagnosed cancer in 1981 and gave her a year to live. She once described how "the world birding started with a death sentence". The mother-of-four set off on an almost non-stop series of journeys to exotic locations - and when her cancer went into remission she continued travelling.
Mrs Snetsinger, who was in Madagascar with a specialist bird-watching tour group, had in her final days added five extra species to her world list, including the rare helmet vanga (Euryceros previstii), a shrike- like bird found only in the eastern part of the island.
The UK's leading rare bird seeker, Lee Evans, who earned himself a Guinness Book record for the number of bird species seen in Britain in a year (359 in 1990), got to know her during his world travels and spoke of being "deeply saddened" by her death.
"In my several meetings with her at various points around the globe, I was always bowled over by her sheer enthusiasm for birding," Mr Evans said.