For purposes of the graph, "Fledged" chicks are those which
have reached the age of 7 or 8 weeks at one survey date, and in the next
survey they are absent from the nest. The "fledged" chick numbers
will be added together at the end of the season.
The graph will be updated as surveys occur.
Clicking on the graph will open it in a new larger window or tab.
Thanks to Glenn Woodford for this video of
a survey in action: