Fairy-Wren Babies Need to Call Password for Food

Password culture is not unique to the tech-savvy human race, so it seems. Fairy-wren babies need to utter a password if they have to be fed by their mother, a new study reveals.

Researchers from Flinders University in Australia have found that female superb fairy-wren birds (Malurus cyaneus) teach a single unique note to the embryo in their eggs before they are hatched, so that the chicks can incorporate it in their "begging calls" for food after birth.

The password helps the mothers to identify their own chicks from the offspring of cuckoos that invade their nests. Parasitic cuckoos are known to lay their eggs in other birds' nests. Once the mother fairy-wren finds that the chick is not its own, she will abandon the nest and start a new family again.

"Parents and others attending the nestlings will only feed them if their begging calls contain the learned password," Sonia Kleindorfer, of Flinders University in Australia, said in a statement.

The birds teach the song to their mates and helpers by singing a "solicitation song" away from the nest. Experts also noticed that the begging calls of the chicks differ from one nest to another.

When they carried out cross-fostering experiments, where they swapped the eggs from one nest into the other, they found that the chicks made begging calls that was similar to the calls made by their foster mothers, and not by their own mothers, which suggests the password is actually learned.

Experts also conducted another experiment where they placed a loudspeaker playing a different begging call under a nest. They noticed that the birds did not feed their own chicks when they heard the wrong call from the loudspeaker.

This is indeed an interesting discovery which goes to show that the female fairy-wrens not only pass on their genes to their chicks but are also able to pass on the cultural trait to its offspring even before they are born, said the researchers.

The findings of the study, "Embryonic Learning of Vocal Passwords in Superb Fairy-Wrens Reveals Intruder Cuckoo Nestlings," are published online in the journal, Current Biology.