Fairy wren mothers set up an "IQ test" for their babies, and reward good learners with more food. Here's what's even crazier: the IQ test starts when the baby birds are still inside the egg. This is possible because even before birds hatch, they are nonetheless learning from sounds in their environment. (And birds aren't unique; even human babies in the womb begin to learn language from their mother!)
While the mother bird incubates her eggs, she often makes a specific repeated sound: "CHEEP CHEEP." Once the babies hatch, they adopt this CHEEP CHEEP as their distinctive "FEED ME" cry.
Amazingly, researchers writing in The Aukfound that the more similar the begging call to the call taught by the mother, the more food the mother doled out (see graph here)! In other words, babies that learned best get rewarded for it, somewhat akin to human parents who pay their kids for getting As. It is important to note that this was tested indirectly-- through an experiment that used playbacks to test a mother's food provision in response to call playbacks that ranged from dissimilar to very similar. Nonetheless- how intriguing!
The senior author asks, “As a parent, do you invest in quality offspring, or do you invest in offspring that are in need?” She concludes that if you're a fairy wren, it looks like you aim for quality.
Thank you to William Bernhardt for sending along this paper!
It turns out that baby red-backed fairy wrens also emerge chirping like their moms. And the more frequently that mothers had called to their eggs, the more similar were the babies' begging calls. In addition, the team set up a separate experiment that suggested that the nestlings that most closely mimicked their mom's voice were rewarded with the most food.