The songs that birds chirp may be genetically determined, Agence France Presse reports.
As they report in Nature Ecology and Evolution, Uppsala University's David Wheatcroft and Anna Qvarnström swapped eggs from the nests of pied and collared flycatchers. The pied flycatcher eggs were then raised by collared flycatchers and vice versa.
Despite being raised by different birds, the nestlings were more responsive to the songs of their genetic relatives, the pair reports. This suggested to the researchers that social experience didn't influence early song discrimination. AFP adds that when the birds reached adulthood, they then sang songs of their own species.
"Nestlings discriminate songs... even when they have been raised completely by parents from the other species," Wheatcroft tells AFP.
He adds that this suggests that being able to tell the difference between songs is not learned. "Song discrimination depends on genetic inherited factors," he says.
Wheatcroft and Qvarnström note in their paper that this can stabilize reproductive isolation.