Scientists have found that certain species of bird sing to their eggs before they hatch. Zebra finches sing to their eggs in hot weather, possibly signaling the temperature to their developing chicks. This phenomenon, which has been previously unstudied, is detailed in a paper just published in the journal Science.
Developing embryos have been shown to be able to hear and respond to external sounds. Human fetuses, for example, can perceive and remember sounds from inside their mother’s womb. Zebra finches have been observed singing to their eggs. Researchers noticed that this happened at higher-than-average temperatures but the reasons for the behavior were unknown.
A team of researchers studied a group of zebra finches. They found that the finches sang to their eggs when ambient temperatures went above 78 degrees Fahrenheit. Eggs in the nest are kept at a constant temperature of 98.6 degrees and are not affected by the air temperature. The team wondered if the finches’ calls somehow prepared the chicks for the environmental conditions they’d face after hatching. They recorded the parents’ songs and played them to eggs in an incubator. Another set of eggs was instead exposed to regular zebra finch calls and not the temperature-specific songs.
Interestingly, the eggs that listened to the special songs hatched at a smaller weight and grew slower than the control group. This would actually be beneficial in hot weather since smaller birds cool down faster. Further analysis revealed that the birds in the experimental group were more reproductively successful as adults. The birds that heard the special song ended up having more offspring than their counterparts that heard regular bird calls.
The research team isn’t completely sure why the songs have such an effect on the chicks’ growth and adult reproductive success. The authors speculate that the parents’ songs somehow affect embryonic development. The findings may represent an important adaptation to increasing temperatures due to climate change.
Mylene M. Mariette & Katherine L. Buchanan. Prenatal acoustic communication programs offspring for high posthatching temperatures in a songbird. Science (2016).