Imma Perfetto
Cosmos science journalist
We’ve come a long way from the fantastical idea that birds migrate to the Moon when they disappear each northern hemisphere winter. But while migratory bird behaviour in Europe and North America is widely studied, comparatively little is known about the southern hemisphere.
Now, scientists have finally revealed the existence of a structured bird migration system in Australia. They used 16 years of weather radar data from Australia’s Bureau of Meteorology to monitor bird migration patterns from Tasmania to northern Queensland and show that it is distinctly different to northern hemisphere migrations.
“We were very excited to discover millions of birds migrating in Australia each year, escaping cold southern winters by moving up the east coast,” says Xu Shi, a University of Queensland (UQ) PhD candidate who led the study published in the journal Current Biology.
“Birdwatchers have known for a long time that some Australian birds migrate, but never before have we been able to study the phenomenon so clearly.
“Weather radars can tell us how many birds are flying, when and in which direction they’re moving.”
The team analysed data from 10 weather radars to investigate the pattern of bird movement for day and night across the whole year. While they found that most bird movements happened in the autumn and spring, the patterns of migration varied from year to year.
“The data showed lots of variation in migration direction, timing, and intensity from year to year when compared to northern hemisphere birds, which are very rigidly tied to seasons,” says Shi.
“For example, the tiny Silvereye, Zosterops lateralis, migrates from Tasmania to as far as southern Queensland.
“But they might not all do that every year and sometimes they migrate shorter distances.”
Unlike in the northern hemisphere, the researchers suggest that migration in Australia is dominated by “facultative migrants”. Rather than being obligated to migrate, these are birds that may “adjust their decision, timing, and the distance of migration in response to environmental cues, such as food availability and meteorological and climatic conditions”.
They also found that, unlike birds in the northern hemisphere, many Australian birds migrate during the day rather than at night. The researchers are not yet sure why this is.
Study co-author Professor Richard Fuller of UQ says the discoveries pave the way for conservation efforts to protect Australia’s birds.
“Birds that migrate within Australia are often overlooked by legislation, and until now we’ve known very little about which species migrate, where they go and when they do it,” says Fuller.
“Our research shows that a considerable number of birds migrate within Australia, which highlights the need for more research into their migration patterns.
“By enabling researchers to further explore how climate change and environmental shifts affect bird migration, our findings can help us better protect birds in Australia and globally.”
