Bird migration is one of the great mysteries of the world but research conducted by an environmental scientist at the University of Technology, Sydney has shown that genetics, not learned behaviour, fuels these flights.

An acknowledged pioneer researcher in southern hemisphere bird migration, Dr Ursula Munro, has just finished an 18-month study of behaviour differences between migratory and non-migratory birds of the same species, and she has reached some dramatic conclusions.

Dr Munro has studied the beautiful little silvereye bird, with its olive back, russet flanks and circle of white feathers around its eye.

Within the silvereye species, there is a subspecies that migrates and one that does not. The Tasmanian silvereye braves the Bass Strait and can fly as far as Queensland in late March, returning in early September. The mainland silvereye stays in the same area of NSW. This anomaly gives Dr Munro good basis for research.

Dr Munro has kept 17 Tasmanian birds and 15 mainland ones in individual cages for the past 18 months. Each bird was kept in a controlled environment, with even light, no parents, and no natural habitat. Some of the birds were juveniles when caught, so they could not have learned migration behaviour from their parents.

"They had no access to the environment, rains or flowering patterns," Dr Munro said. "If a bird migrates, do they learn it? Or are they genetically conditioned to prepare for the long trip? By my results, migration must be influenced by the birds’ genetic make-up. I’m getting striking differences in orientation, moult and body condition between migratory and non-migratory silvereyes."

In the controlled environment the Tasmanian birds still prepared to travel, showing clear directional preferences, increasing food intake in advance of the Spring migration and moulting at fixed times. The mainland birds were "all over the place" in their orientation and moulted over a much longer time.

"This is the first time that anything like this has been done on migration here in Australia. We know so little about it that it makes it very difficult to protect our migratory birds and develop management plans for them," Dr Munro said.