Like a human child learning to speak a language, juvenile songbirds also need to learn their songs by first listening to their parents and other adults of the same species.
As with humans, this learning process results in small changes from generation to generation, leading to characteristic differences in song amongst geographically distinct populations of the same species. These are called song dialects.
Now, a new study has found that nestling pied flycatchers (Ficedula hypoleuca) as young as 12 days old, preferentially react to hearing songs from their own dialect, compared to the songs of another species and even different populations in their own species.
By broadcasting songs to almost 2,000 nestlings and observing their responses, researchers were able to show that young flycatchers respond to songs that are more similar to those from their own dialect, by begging for food.
“These results establish that birds are ‘tuned’ from a young age to recognise their own populations’ songs, which focuses subsequent learning,” says lead author of the study David Wheatcroft, an Associate Professor in the Department of Zoology at Stockholm University, Sweden.
Pied flycatcher song is produced by males and plays an important role in female mate choice. They co-occur with the closely related collared flycatchers (F.albicollis), but occasionally they crossbreed to produce infertile offspring.
Researchers analysed songs from 168 individual pied and collared flycatcher males to get an understanding of song variation, and found that pied flycatcher songs from seven European populations form clearly defined dialects.
They found that young pied flycatchers could discriminate against the song of the collared flycatchers even if the two species did not co-occur in the same area.
“We have shown that interactions with collared flycatchers in particular are not required for the emergence of discrimination against their songs,” the authors write.
The dialect-specific response may help to prevent pied flycatchers from learning the songs of closely related species, and likely promotes a pre-mating reproductive barrier between the collared and pied flycatcher.
How are they doing this? Wheatcroft says that an explanation could be that nestlings recognise their own dialect innately.
“If differences in early song responses among populations are truly innate, it would suggest a remarkable co-evolution between a cultural trait and the genes underlying it.
“Singing the local dialect is thought to help adults attract appropriate mates.”