"As a behavioral ecologist studying nestlings in bird nests, I have always known that baby birds respond to sounds in their environment, whether it be the rustling of leaves or the parents calling out to them," Mark Erno Hauber, one of the researchers who carried out the study, told Medical Xpress. "Yet, when I became a neuroscientist, I was surprised to find that avian neurobiologists considered the nestling bird an auditory tabula rasa—without the ability to fully hear and process acoustic stimuli."

The lead authors of the recent paper are Ph.D. students Nick Antonson from University of Illinois and Moises Rivera from City University of New York. In collaboration with Hauber and other biology researchers, these researchers have been investigating both nesting and embryonic hearing in birds for over 20 years. Their studies focused on a variety of species, ranging from cowbirds to fairy-wrens and zebra finches.

"The current study came about because recently, we discovered that the auditory forebrain in zebra finch embryos inside the egg is activated to conspecific song playbacks over silence," Hauber said. "We preserved the study's specimens, and for the current study, we assessed whether epigenetic markers were also detectably altered by different playbacks of con- vs. heterospecific songs (and silence). Interestingly, we found less genome-wide methylation in response to zebra finch songs than to heterospecific songs."