Finches and Bad Parents: Why Some Birds Don't Listen
When it comes to zebra finches, you have your highly social ones, which learn their foraging skills from their parents. But it turns out that anxious finches, which are exposed to high levels of stress hormones soon after hatching, will learn only from adult birds totally outside of their natural-born family--in fact, they ignore their parents' guidance and learn skills from a network of other adult finches.
Cambridge University researchers recently wrote in the journal Current Biology about these findings regarding the behavioral changes in young Taeniopygia guttata. They believe that spikes in stress during early development may serve as a cue to the young birds that their parents are doing something wrong. At that point, the fledglings switch their social learning strategy to learning from other flock members.
This change of path may help the juveniles avoid a negative feedback loop, possibly the result of low-quality parental investment or food scarcity at birth.
These changes could impact important population-wide processes, such as migration efficiency and the establishment of animal culture, the researchers said in a release.
"These results support the theory that developmental stress may be used as an informative cue about an individual's environment. If so, it may enable juveniles to avoid becoming trapped in a negative feedback loop provided by a bad start in life - by programming them to adopt alternative, and potentially more adaptive, behaviours that change their developmental trajectories," said Dr Neeltje Boogert of Cambridge, a co-author of the study, in the release.
Scientists looked at 13 broods of zebra finch hatchlings, feeding half of them with physiologically relevant levels of cortisone, the stress hormone, dissolved in peanut oil; and the other half with just plain peanut oil-for 16 days, from the age of 12 days old, the release said.
Once the chicks were old enough to eat on their own, they were released with their families into one of two aviaries in which they could freely fly. Researchers tracked their movements using radio tags called PIT tags (Passive Integated Transponder), about the size of a grain of rice. When a bird visited a feeder, its PIT tag was scanned, the release noted.
From these PIT scans, the scientists found that the juveniles that received cortisone from a young age spent more time with unrelated birds and were less choosy about which birds they foraged with; the control group stayed near their parents and foraged with the same flock mates, according to the release.
When the birds were asked to solve a puzzle, the control group mimicked their parents in solving the puzzle. The developmentally stressed chicks copied unrelated adult birds and didn't look to their parents at all.
"If developmentally stressed birds occupy more central network positions and follow many others around, this might make them especially efficient spreaders of disease, as stressed individuals are also likely to have weakened immune systems," said Boogert, in the release.
Next, scientists will explore implications for the spread of avian pox or flu, and other important population-level processes.
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