This video from Australia is about superb fairywrens.
From the Cornell Lab of ornithology in the USA:
Baby Birds Learn Calls From Their Mothers While Still in the Egg
It turns out humans aren’t the only species that can hear sounds before birth. New studies from Australia find that some mother fairywrens call softly to their eggs. The chicks not only hear their mothers, they actually begin learning parts of her calls while still inside the egg. The calls may later serve as a sort of family password once the birds hatch. Read the story and listen to the calls.