A world-first Deakin study has revealed how early trauma in birds affects their ability to memorise songs that are crucial for their survival – and how this could have implications for human development.
These new findings, recently published in Proceedings of the Royal Society of London B: Biological Sciences, could be the key to understanding the effects of early-life stress on speech and language development in children. Humans are the only other group of animals distinct from birds to show dedicated parts in the brain for vocal learning, so linking these two wouldn’t be unreasonable.
Professor Kate Buchanan, lead researcher and avian behavioural ecologist, emphasises the importance of this discovery, saying songs remembered by birds are used for their day-to-day survival. Mating songs, as well as calls to protect each other from predators, are all learnt from the father from a young age. However, due to increased stress from changes in their climate and habitat, their ability to accurately recall these songs is being impacted.
Buchanan mentions how this pattern can be seen in human language development.
“Of course, it would be unethical to run experiments with children to determine if stress affected vocal learning. But the data we have gathered in this study suggests that stress affects how neural connections form, and when and how auditory memories are formed. It’s entirely plausible that such effects are common to birds and humans.”
Although it’s already known that early-life stress affects human speech and language development, the new research will be able to give us an indication as to the mechanism behind the process. As part of the study, two groups of zebra finch nestlings were observed, one in normal conditions, the other with restricted food supplies. The latter group grew more slowly at first, but caught up near the fledgling period and did not differ in mass when they became adults.
However, when tested on their ability to respond to a recording of their father’s song, the group on restricted supplies were less responsive, finding it harder to recognise the acoustic signal. Buchanan added that, “the brain’s response to the playback of familiar, recently heard songs was reduced in nutritionally deprived birds too, showing that early-life stress also affects the ability to recognise and remember sounds learnt in later life.”
Co-author Dr Alizee Meillere suggests that these findings suggest that those who experience early-life stress have a decreased ability to recognise other members of their species for as opposed to those who grew in ideal conditions.
“They are social birds,” states Meillere, “They need to know who is part of their group in order to recognise them, to settle into a territory and integrate into the population. So, learning this dialect is important.”
This goes back to the significance of birdsong in communicating and attracting a mate. If the males fail to have a complex song, female birds will disregard them. It could also lead to infertile eggs from cross-species mating, which would not happen if the song is memorised correctly.
With increasing unstable conditions due to climate change and other environmental degradation, birds have had to cope with more stressors, and only through understanding how these affect them can scientists better protect and ensure their survival.
Long-term experiments will be conducted as part of Deakin’s further research to observe if and how these impacts are transmitted across generations. Hopefully, this would also shed more light on our development as human beings, and how similar stressors can affect us in our day-to-day life.