Ellen Phiddian
Cosmos science journalist
In the 1940s and 50s, Dutch scientist Albert Perdeck kidnapped more than 14,000 starlings and kicked off a debate that rages in ecology to this day.
Do the birds learn to migrate, or is their behaviour instinctive?
A new study, published in Biology Letters, might have settled the matter.
Perdeck and his team captured starlings in the Netherlands, which were on their winter migration southwest towards Britain and France. They attached rings for identification, and transported the birds to Switzerland and Spain where they were released in different groups.
Perdeck wanted to see if relocating the birds would change their final destination.
“Adult starlings adjusted their migratory orientation to reach their normal wintering areas,” explains lead author of the new research, Morrison Pot, from the Netherlands Institute of Ecology, who has re-visited the debate.
“Young starlings continued in a south-westerly direction – the direction they would have chosen when departing from the Netherlands – and reached ‘wrong’ destinations in southern France and Spain.”
So, were the juveniles born with an inherent drive to head southwest? Or were they copying other local starlings?
“Starlings are highly social animals and, according to some experts, the relocated young starlings may just as well have joined a flock,” says Pot. “If true, the migratory route is largely learned instead of inherited.”
Pot and colleagues headed to archives to examine data on local Swiss and Spanish starlings, which was unavailable to Perdeck when he was publishing his findings.
The researchers found that the relocated starlings had different migration paths to the Swiss and Spanish birds.
This means that the juvenile starlings were not copying other birds, but headed southwest of their own volition.
“Starlings travel independently and decisions about where to go are not overruled by the migratory behaviour of others,” says Pot.
This is backed up by another recent study led by some of Pot’s colleagues which found that starlings mostly navigate at night, making it harder to copy each other.
“In times of rapid changes in global climate and land-use, it is of great importance to understand whether migratory behaviour is largely inherited or learned,” says senior researcher Henk van der Jeugd, head of the Dutch Centre for Avian Migration and Demography.
“Although starlings are numerous and widespread birds that have adjusted to human dominated landscapes, their migratory behaviour is likely less flexible.”