We posted last week about adult male Zebra Finches teaching their young with "baby talk." Now here's another post about bird learning, this one about how the mothers of two species of fairywren call to their chicks even before they hatch—and yes, the unborn chicks seem to learn the call.
Before you get too skeptical, remember that recent research has demonstrated that human babies can learn speech sounds at 30 weeks of gestation—that is, before they're even born.
Now, to birds. Nine species of fairywrens live on the Australian continent, where they frequently show up in suburbia. They're small songbirds, and the males are often deep blue or red. Diane Colombelli-Négrel and Sonia Kleindorfer, of Australia’s Flinders University, performed a series of experiments on the Superb Fairywren (Malurus cyaneus).
First, they discovered that Superb Fairywren embryos seem to pay attention when their mothers call to them: their heart rate lowers, just like it does in humans and other animals when they're paying attention. The researchers then investigated the heart rate in a different fairywren species, the Red-backed Fairywren (Malurus melanocephalus). They were joined by Jenélle Dowling and Mike Webster from the Cornell Lab of Ornithology.
Female fairywrens start calling to their unhatched chicks soon after they finish laying, and they stop calling several days after the eggs hatch. Later, when the hatched chicks beg for food, they make some of the same sounds they heard in the egg. The obvious question is, do the chicks really learn their mother’s calls, or do they make these sounds by instinct?
To answer this question, the researchers switched Red-Backed Fairywren eggs among a group of nests to see whether the chicks would call like their genetic mothers (by instinct) or like their foster mothers (by learning). It turned out that the chicks' calls were more similar to those of their foster mother.
Why have a similar call? Well, the next study determined that Red-backed Fairywren parents give more food to chicks whose calls are similar to their own. Since cuckoos often lay eggs in fairywren nests, having a "password" can help parent fairywrens know which chicks are theirs.
Next, the researchers investigated whether adult fairywrens retain any of the call information they learned in the egg. It is commonly believed that chicks don't start learning their adult songs until they're at least 10 days old. With the aid of computer acoustic analysis, the researchers found that the songs of young adult fairywrens more closely resembled the songs of their mothers than they did any other females in the same population. This "family resemblance" might help fairywrens recognize one another so they can share information about resources and dangers. It could even help prevent inbreeding.
These startling discoveries about in-egg learning are just the beginning of what could be further study in embryonic learning in other birds and mammals.
Check out this article from the Cornell Lab of Ornithology for more details on the fairywren research and some awesome sound.