Mother Fairywrens Teach Chicks in Their Shells

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. 

Female Songbirds: Quiet for Good Reason

Female birds are capable of song in 71% of songbird species, So how come we don't hear them as often as we hear the males? New research indicates that sometimes female songbirds have good reasons to stay quiet. 

Sonia Kleindorfer, a behavioral ecologist at Flinders University in Adelaide, Australia, studied the singing patterns of female and male Superb Fairywrens (Malarus cyaneus), a small Australian songbird species. Like the females of many species, female Superb Fairywrens often sing for territorial defense, sometimes even when they're on their nests. They use a melody known as a "chatter song." The male uses it too, but he is not as often near the nest when he sings.  This is a key difference, since singing alerts predators such as rodents, cats, and foxes. Kleindorfer investigated whether male singing or female singing poses a greater risk.

During the nesting seasons of 2013 and 2014, Kleindorfer and her colleagues monitored male and female singing on and near 72 wild Superb Fairywren nests, as well as the eggs and chicks in the nests. The scientists counted a nest as “attacked” if eggs or chicks vanished in under 25 days. In other words, if eggs disappeared unhatched or chicks disappeared before they were capable of fledging, researchers assumed they'd been eaten. 

Kleindorfer's team leaned that both males and females sang the chatter song more often when they were just beginning to nest. They sang it less often when they had eggs and chicks in the nest, and with one major gender difference: The males sang away from the nest and the females near or inside it. In fact, some females never sang at all, and some sang only in response to their noisy mates. To put it differently, the females sang less when doing so would endanger their nests. Proof? The scientists baited artificial nests with quail eggs and broadcast female chatter songs infrequently (six calls per hour) and frequently (20 calls per hour). Predators ate the eggs at 40% of the "frequent" nests, but at only 20% of the "infrequent" nests: the quieter nests were safer for the kids. 

Jordan Price, a behavioral ecologist at St. Mary’s College of Maryland, posits that danger to the nest could be the reason that female songbirds of other species sing far less than their partners—or not at all—when they're the primary on-nest parents. It's even possible that, generally, male songbirds sing not to attract mates but simply because there's no reason for them not to. The females, on the other hand, have to be more wary.