Could prenatal sound discrimination predict vocal complexity later in life?

Background: Greater complexity of the learned vocal repertoire has been shown to increase mating and territory defence success in songbirds. Vocal learning in some songbird species begins in the egg and these songbird embryos can discriminate the sounds of different birds. Here, we test if prenatal sound discrimination positively correlates with song complexity in the Superb Fairy-wren (Malurus cyaneus). We use a habituation/dishabituation approach in natural and cross-fostered nests to measure prenatal sound discrimination of female vocalisations and later quantify observed song repertoire in fledgling sons and daughters. Results: Superb Fairy-wren fledglings produced learned songs consisting of 6-11 different elements by 12 weeks of age. Using multiple regression analysis, both prenatal sound discrimination strength and parental song complexity (total number of vocal elements) positively correlated with a fledgling's song complexity. The number of parental vocal elements was unrelated to the embryos' sound discrimination score. Conclusions: Prenatal sound discrimination strength was positively related to vocal complexity later in life. From previous research, we know that individuals with greater learned vocal complexity may have higher fitness. Therefore, characterizing the causes of prenatal sound discrimination can inform our understanding of fitness trajectories when phenotypes are shaped by learned cross-generational experience. Future research should explore causes of variance in prenatal sound discrimination.