It can take years of practice for birds to perfect the melodic songs passed down from their parents. However, it seems some birds get a head start by learning to imitate their parent's calls while they are still inside their eggs.
Learning to mimic their parent's songs is essential to all basic social interactions, including finding a mate, warning neighbors of predators and recognizing relatives. While such advanced learning has previously been observed in Superb Fairywren nestlings, researchers were interested to see if the behavior extends to other species, too. So the recent study, led by researchers from Flinders University, Hunter College, and Cornell University, focused on the birds' close relatives: Red-backed Fairywrens.
While observing the birds, researchers found that all Red-backed Fairywren females called to their eggs while incubating them, and for five to six days after they hatched. As a result, the offspring's calls were found to be more similar to their mother's.
"Fairywrens have become a new model system in which to test new dimensions in the ontogeny of parent-offspring communication in vertebrates," said Mark Hauber, one of the study researchers from Hunter College in New York City.
When nestlings produce calls that resemble those of their mother, parents put more effort into feeding their offspring.
With that in mind, researchers hypothesized that fairywen parents could use early call trainings to identify any alien or unwarranted nestlings, such as parasitic cuckoos. However, their study showed that Red-backed Fairywren mothers did not increase calls to their nestlings when more cuckoos were around.
Furthermore, researchers thought that if a nestling's call was more similar to that of their parent's, it would indicate they were the most vigorous and the best learner out of the bunch. Parents would then invest more resources into the ones that demonstrated they were most likely to thrive.
"Because fairywrens have high predation rates, we originally placed microphones under Superb Fairywren nests to record alarm calls against predators twenty-four seven," explained Diane Colombelli-Négrel, one of the study researchers from Australia's Flinders University. "As a result, we discovered embryonic learning in Superb Fairywrens."
Similar methods were used to record the vocalizations of Red-backed Fairywrens from 67 nests across four breeding seasons in Queensland, Australia. Researchers also played back recordings of begging nestlings to test parents' responses.
"Prenatal vocal learning has rarely been described in any animal, with the exception of humans and Australian Superb Fairywrens," said University of Queensland's Dr. William Feeney, who is an expert on the interactions between cuckoos and host birds. "In this study, the authors present data suggesting that, like the Superb Fairywren, Red-backed Fairywrens also learn their begging calls from their mother. This result is exciting as it opens the door to investigating the taxonomic diversity of this ability, which could provide insights into why it evolves."
Their study was recently published in the journal The Auk: Ornithological Advances.
