A 13th-century illustration of an Australasian cockatoo debunks the myth Australia was "a dark continent" and reveals trade routes around the country's north were flourishing as far back as medieval times, a study shows.

Researchers found the illustration in a manuscript that was either written by or belonged to Holy Roman Emperor Frederick II.

It is the oldest-known European illustration of the bird, found in a book dating from between 1241 and 1248, and pre-dating other European illustrations of cockatoos by 250 years.

The manuscript includes 900 drawings of falcons and other animals kept by the emperor. Four of the images are of a white cockatoo — a gift from an Egyptian sultan to Frederick II.

The manuscript includes 900 drawings of falcons and other animals. ( Supplied: Biblioteca Apostolica Vaticana )

Heather Dalton from the University of Melbourne, who contributed to the research published in the journal Parergon, said the find challenged "the British view" that Australia was "a dark continent".

"The significant thing is that this parrot provides a window to a world of quite busy trade to Australia's north," she said.

"The discovery of these images … highlight the fact that during the medieval period, merchants plying the waters just to the north of Australia were part of a flourishing trade network that reached west to the Middle East and beyond."

Dr Dalton said while many scholars were aware the Sultan had given a "white parrot" to Frederick II, few were aware there were surviving images of the bird.

The research team looked at the details, such as the shape of the crest and the colouring of the cockatoo, and concluded it was likely a female — either a sulphur-crested cockatoo or a yellow-crested cockatoo.

Sulphur-crested cockatoos are found in Australia, Papua New Guinea and some Indonesian islands. Yellow-crested cockatoos are native to Indonesia and East Timor.

The International Union for Conservation of Nature considers yellow-crested cockatoos to be critically endangered, with their population estimated to be less than 3,000 globally.

Cockatoos travel well with people, being gregarious and long-lived, making a perfect gift, Dr Dalton wrote.

"In captivity, they can have lifespans of up to 80 years and Australian greater sulphur-crested cockatoos have been known to live up to 120 years," she said.

"The journey along trade routes would have taken years, and their chances of surviving would have been much higher than the majority of animals."