Reading the comments farther down on the page, they indicate that there is quite a difference in age as well with the oldest being two weeks and the youngest 6/7 days.
When I look I usually see between 2 and 4 chicks, although they have 6 chicks. Probably the littlest are tucked down low. There was a person at the nest site yesterday (human on camera) who confirmed the 6 chicks.
