Popular Science is trying to figure out if you can teach a robin to sing like a swallow, or a warbler to tweet like a canary… and, as far as researchers David Wheatcroft & Anna Qvarnström can tell, birds are born with their distinctive songs inside them:
For this study, the researchers examined the pied flycatcher and collared flycatcher, two birds that live on the same island in the Baltic sea. They knew that nestlings in each species would start to visibly respond to their species’ songs as early as 10 days after they hatched. The ecologists wanted to see if swapping out eggs in the nest (and having the other flycatcher species raise them) would affect the birds’ responses to song. In other words, could the baby birds be tricked into learning a totally new birdsong if that’s all they heard after hatching?
But the birds weren’t fooled by the old switcheroo. Collared flycatcher nestlings responded more strongly to recordings of collared flycatcher adults, opening their little beaks and looking around intently for the source of the noise—and basically ignoring the pied flycatcher songs. The pied flycatcher nestlings raised by collared flycatchers behaved in a similar way.
Then, the ecologists took the study a step further. They created hybrids of the two species and found that the resulting hybrid nestlings responded much better to pied flycatcher songs. That suggests to them that there was a genetic component to the song preference.
The full study is published in Nature Ecology & Evolution (abstract is free).