One unhatched egg was left in the nest.
The chick was incubating the egg while the parents were away from the nest. The chick was 6 or 7 days old. We once observed children incubating eggs on June 7, 2021 (See website.). Only one of the three chicks incubated the egg. We would like to know the sex of the chick, but it was not possible. Unfortunately, this egg did not hatch.
It is too early to conclude from this observation alone that the chicks will incubate the eggs. More observations are needed.
The following site showed the other chick incubating the eggs (website).
See the video for the rest of the story. Please subscribe to my channel on YouTube. The name of account is “hachi ai“.