Zebra finches 'sing' to their unborn chicks to warn them of increasing temperatures. Chris Tzaros

According to new research, zebra finch adults sing a special song to their unborn chicks in order to warn them that temperatures are becoming too warm. This could be helping the growing birds prepare for a hotter world brought on by climate change. Uncovering such a mechanism represents an important advance in our understanding of how different species are adapting to climate change.

The ability of zebra finch embryos to hear external sounds allows the "Incubation calling", as it is known, to work. It is just one of many prenatal techniques many animals use to prepare their young for the world they will be born into. Ducks and chickens, for example, are known to 'call' to their eggs, so that by the time they hatch they are able to recognise their parent's voice.

However, little is known about how these kinds of behaviours relate to evolutionary and survival capacities, especially in a rapidly changing environment. Mylene M Mariette and Katherine L Buchanan from Australia's Deakin University, sought to address this lack of knowledge by studying incubation calling.

They hypothesized that these songs help the unborn chicks to anticipate their new environment, which they tested by recording the incubation calls of 61 female and 61 male zebra finches nesting in outdoor aviaries during naturally changing temperatures. They found that the parent finches only called to their eggs near the end of the incubation period and only when the temperature reached 26<sup>C or more.

This special incubation call caused the chicks to hatch sooner, the benefit of this being that it appears easier for smaller birds to cool themselves down in hotter temperatures.