Embryos are still red and slimy already capable of vocalizations. A study published in The Royal Society on Monday, September 6, proves the ability of nestlings not yet hatched to become familiar with the sounds around them and respond to them, in the bud, with small noises.
Researchers sensitized eggs of five different bird species to the music of various bird calls for seven years. All were receptive, with the sounds of their own species eliciting a stronger response from their brains than the song of an alien species. Still nestled in their eggs, these virtuosos are already beginning their vocal learning.© Sciences et Avenir, ROMONA ROBBINS PHOTOGRAPHY Chicks are able to hear sounds when they are still in their shell.
Even the “non-learning” birds remained attentive. Indeed, a historical classification distinguishes two categories of birds. On the one hand, “vocal learners, like Darwin’s finches, are able to invent new songs or imitate those of others. On the other hand, the “non-learners”, the penguins, for example,keep the same repertoire, from their family, all their lives.
Should the classification of birds be reviewed?
This binary system of voice learning is nevertheless considered too simplistic by researchers in recent years. A spectrum that nuances the degrees of vocal learning by species would be more appropriate.
At one end would be, for example, the passerines, able to retain and learn to sing songs broadcast through loudspeakers. At the other, quails that know only the chorus of their kind.
Still, others have a thin inner ear. Gull embryos hear warning cries from their parents. So, as soon as their egg hatches, they are more defensive and are particularly attentive to alarm signals. Zebra finches can see their behavior change in adulthood. It would be modified by the lullabies that their parents sang to them in the embryonic state.
Thus, while it cannot yet be said that this learning changes the behavior of birds after hatching, researchers believe that sound would prepare embryos for life outside the egg.