How young do baby birds recognise family?

A small brown ground finch surrounded by red flowers
The small ground finch on Floreana Island in the Galapagos. Credit: D. Colombelli-Négrel, Flinders University

When do baby birds learn to sing? According to new research, the birds begin to take notes while still shell-bound.

A group of researchers based at Flinders University have found that even inside the egg, the heartbeats of baby birds change when their parents’ calls are played to them.

“This research will hopefully inspire more study into the remarkable capacity of animals to learn sound,” says Professor Sonia Kleindorfer, senior author on a paper describing the research, published in Philosophical Transactions of the Royal Society B.

The researchers examined five different species of bird: the superb fairy-wren, the red-winged fairy-wren, Darwin’s small ground finch, the little penguin, and the Japanese quail.

Fairy-wren hatchlings in a nest
Superb fairy-wren hatchlings in the nest. Credit: A Katsis, Flinders University

“We wanted a range of species among the so-called ‘vocal non-learners’ [penguins and quail] and ‘vocal learners’ [wrens and finches] but also with different lineages and developmental characteristics,” says Dr Diane Colombelli-Négrel, lead author on the study.

Vocal learners are creatures that learn to copy vocal noises from a tutor, while vocal non-learners figure out how to do it without being taught.

Read more: “You bloody fool!” The musk duck that learnt to swear

Red-winged fairy wren in the undergrowth
The red-winged fairy wren. Credit: Marina Louter

The researchers used a monitor to determine the heart rates inside 109 eggs from wild birds while they played different sounds.

“We measure heart rate in birds using a non-invasive technique developed by our team,” says Colombelli-Négrel.

“We use a digital egg monitor that measures light absorption changes due to embryonic blood flow.

“This method allows us to measure heart rate in the field and for eggs to be returned to their nests for hatching without any negative impacts.”

The researchers found that when the eggs were played calls from their own species, the embryos’ heart rates changed. This was particularly the case with the vocal learning birds.

Little penguin in dappled light
A little penguin on Troubridge Island. Credit: D. Colombelli-Négrel, Flinders University

Additionally, all species, became “accustomed” to unfamiliar bird calls: their heart rates reacted a lot initially, then calmed down as the sounds continued to be played.

Kleindorfer says this research has interesting implications for how animals learn sounds.

“By moving the time window for sound learning to the prenatal stage, this research direction opens pathways to measure neurobiological downstream effects of early auditory experience on behaviour and information processing.”

Colombelli-Négrel says the Bird Lab is keen to find out whether this inside-egg learning applies to other species of bird and are now listening in on in-nest behaviour-calling from mother birds in seven fairy-wren and grasswren species.

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