Some birds learn mother's calls even before they hatch

Some birds start learning to imitate their mothers' calls even before they hatch, a new study has found.
Researchers from the Cornell University in US and Flinders University in Australia had earlier discovered that Superb Fairy-wren nestlings learn to imitate their parents' calls while still in the egg.
They wanted to see whether the behaviour extended to other species and to learn more about its ecological context. So they turned to the related Red-backed Fairy-wren.
All Red-backed Fairy-wren females in the new study called to their eggs while incubating, and most continued to call to their nestlings for five to six days after they hatched.

As a result, mother and offspring calls were more similar than would be expected by chance. Parents also put more effort into feeding nestlings with calls similar to their own.
"Fairy-wrens have become a new model system in which test new dimensions in the ontogeny of parent-offspring communication in vertebrates," said Mark Hauber from Hunter College in New York.

Though the researchers had hypothesised that fairy-wren parents could use calls to identify alien nestlings, the result of eggs placed in their nests by parasitic cuckoos, the rate at which Red-backed Fairy-wren mothers called to their eggs did not increase significantly when more cuckoos were present in the habitat.

Researchers speculate that the similarity of nestlings' calls to their own could also tip parents off about which nestlings are the most vigorous and the best learners, so that they can invest more resources in the ones most likely to thrive.
"Because fairy-wrens have high predation rates, we originally placed microphones under Superb Fairy-wren nests to record alarm calls against predators twenty-four seven," said Diane Colombelli-Negrel from Flinders University.
"As a result, we discovered embryonic learning in Superb Fairy-wrens," she said.
When they turned to Red-backed Fairy-wrens, they recorded vocalisations from 67 nests across four breeding seasons in Queensland, as well as playing 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 Fairy-wrens," said William Feeney of the University of Queensland.
The study was published in the journal The Auk: Ornithological Advances.