When baby zebra finches are stressed in their early life, they stop listening to their parents. This might sound like typical teenage behavior, but the effects of stress early in life for these finches surprised researchers when they observed their behavior as young adults.
"No one has really looked at how early-life stress might affect social behavior later on," Dr Neeltje Boogert told IFLScience. Boogert, from the University of Cambridge, authored the study alongside her colleagues from the Universities of Oxford and St Andrews. The results are published in Current Biology.
The study contained 13 broods of zebra finch hatchlings. Within each brood, half of the chicks were fed peanut oil: these were the control chicks. The other half were fed peanut oil mixed with dissolved corticosterone: a hormone associated with stress. The hatchlings were fed this oil treatment every day for 16 days when they were 12 days old.
When the finches became independent, they were each fitted with a tiny chip so that the researchers could monitor them. For the next 40 days, the zebra finch families could interact with each other in an aviary, out of isolation so that the researchers could see how the birds searched for food and interacted. The researchers noticed some sharp differences between the control chicks and the artificially stressed chicks.
The control chicks stayed close to their parents and their flock. However, the stressed finches were more likely to ditch their family and spend time with birds unrelated to them.
The scientists set up a test to see how the two different types of birds decided to solve problems. They set up a tray with regions filled with a tasty spinach treat which was covered with a lid that the birds had to remove to reach the food.
Zebra finches solving a hidden food puzzle. Dr Neeltje Boogert.
The stressed out birds were actually faster than their control counterparts at learning how to get to the food. Even without copying their parents.
Boogert expressed how her prediction of the stressed birds' behaviors was subverted, "I expected them to not have too many friends," or to be "socially marginalized if you will."
"And I was expecting that they would be a bit dumb, that they wouldn't know what to do. But it turns out that actually the stressed out birds are much faster at solving the puzzle, and they've got a social learning strategy,
"Instead of copying their parents what the stressed birds do is copy exclusively unrelated adults. And they supplement this social learning with individual learning, so they don't only copy, they're also more inventive."
The researchers postulate that this success is because the stressed birds are used to depending on their own ability to try new things. Alternatively, these finches could be copying behavior from a larger pool of adult birds and are increasing their chances of success. Whatever the reason, not one of the stressed finches looked to their parents for help.
Boogert wants to expand the field of her research from an aviary to the wild. Studying birds in an aviary is better than isolation, but the wild is better still. She has an inkling that these stress patterns in young birds in the wild may have some unexpected and potentially deadly consequences.
"There might be effects on, for example, disease transmission. So it appears that these stressed out birds are highly social, so they follow around unrelated birds." This could make the transfer of diseases such as avian flu spread much more rapidly among birds that have suffered stress as chicks.