Originally Posted by
nirofo
It almost certainly won't be a flying juvenile Blue Tit with a ring on just yet, they've only just started nesting this year. They will normally lay 7 to 10 eggs, but even up to 14 occasionally, incubation is usually 14 days and fledging of the nidicolous young is about 19 days. So, working that back to when she layed the first egg, that's 19 days to fledging, plus 14 days incubation, plus lets say an average of 10 days to lay 10 eggs, (1 per day). Total to one fledgling leaving the nest = 43 days or 2nd March for first egg , it's possible but extremely unlikely ? The bird you saw was probably a poorly marked adult individual, possibly a female as they are not usually so well marked as males.