Things birds pick up from their parents while still in the egg may play a larger role than once thought.
Birds may be able to provide information about the weather to their offspring through the eggshell.
This process is called embryonic learning and could in turn help baby birds prepare for the forecast.
The song appears to keep chicks from growing too large when the weather is hot and even affects the number of baby birds in the next generation.
The new study on zebra finches found that they sing to their eggs late in development to warn them about the warm weather once they hatch.
It was already believed that birds like chickens or quails, who have to fend for themselves when hatched, can hear through eggs.
This recent development shows that even birds that depend on their parents still receive weather advisory through the eggshell.
“This acoustic signal is potentially being used to program the development of offspring,” says Kate Buchanan, the senior author of the new paper.
“Hearing the call affects your rate of growth relative to the temperature that you experience.
“Animals have very subtle ways of inferring how the environment is likely to change, and (being able) to develop and adapt accordingly,” she added.
We’re only looking at the tip of the iceberg in terms of what we recognize so far… It is quite paradigm-shifting.”
They placed microphones in 125 nests of captive zebra finches living in an outdoor aviary.
The researchers realised that chicks might be listening from inside their eggs when they noticed that their parents sing a specific song when they were alone with the eggs.
The finches only sang this song when the weather was warm, and when their chicks were close to hatching.
“Because they only do it toward the end of the incubation, it really looked like they do it to communicate with the egg,” Mariette says, rather than just calling out because they are hot.